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ntonssiOHAL rufss or the corps of msisssBS. v. s. abut
No. t»
ENGINEER FIELD MANUAL
PARTS I-V!I
I RECONNAISSANCE
IL BK[DC.£S
ra. ROADS
IV. RAILROADS
V. FIELD FORTmCATlON
VI. ANIMAL TRANSPORTATION
VIL TABLES. W'OCHTS. MEASURES, AND
SPEanc GRAvmcs
PKETAAU) liNDEH TH£
DIKECnON OP THE CHCT OF CNCIKEf J13. U, a. ARMV
rPTH il*EVEEDJ EOmCN
I
.7)3
PROFESSIORAL PATERS OF THE CORPS OF EN6INEEKS. U. S. ARMY
No. 39
J ENGINEER FIELD MANUAL
I PARTS I-VII
I. RECONNAISSANCE , ;
IL BRnXiES
I IIL ROADS
i IV. RAILROADS
V. FIELD FORTIFICATION
VI. ANIMAL TRANSPORTATION
VH. TABLES. WEIGHTS, MEASURES, AND
SPEanC GRAVITIES
FIFTH (REVISED) EDITION
WAR DEPARTMENT.
Document Ko. 355.
Office of the Chief of Engineer »,
X
V
n:
War Dbpartmbnt,
Office of thb Chief of Staff,
Wctshington, Novemher 19, 1909,
The Engineer Field Manual, United .States Army, prepared under
the direction of the Chief of Engineers, United States Army, is
published for the information and guidance of all concerned ; it will
not be modified except by specific authority given in each case.
Any changes or suggestions that may occur to officers or others
using the manual will be submitted to the Chief of Engineers for
consideration in connection with the publication of future editions.
By order of the Secretary of War :
J. Franklin Bell,
Major Qeneral, Chief of Staff.
3
313648
War Department,
Office of thb Chief of Engineers,
Washington, Maroh 12, 1907,
The Adjutant General.
Sir : 1. By authority of the Secretary of War, six parts of the
Bneineer Field Manual, compiled under the direction of this office
by Lieut. Col. Smith S. Leach, Corps of Engineers and General Staff,
have been published In five separate volumes. These parts are :
Part I, Reconnaissance; Part II, Bridges; Part III, Roads; Part IV,
Railroads, and Part V, Field Fortification (in one volume) ; and
Part VI, Animal Transportation. Each of these six parts received
the approval of the Chief of Staff before its publication.
2. It is now desired to publish under a single cover these six
parts, revised and corrected, for issue to the service when ready for
distribution.
3. In addition to the correction of such Qprors as have been dis-
covered in the original editions it Is proposed to add some new matter
to bring the work up to date. The most important addition is a
description of the new types of instruments adopted in 1906. It is
also desired to add, In Part I, a brief description of the new military
survev of Cuba ; some additional topographical signs and symbols
recently prescribed by the General Staff, and a brief account of the
new system of angular measurement In mila adopted for position
finding by the Field Artillery ; to Incorporate, in Part II, a very
useful table of dimensions of floor systems for stated loads and
spans, and to incorporate, in Part V, a plate and description of the
Fort Riley redoubt, which presents several excellent features of
design. It Is proposed to add the new matter at convenient places
as nearly . in its topical relation as possible, but under a caption
"Addenda, 1907."
4. The mechanical work involved in the preparation and publica-
tion of this revised edition would be, roughly, as follows : Drawing
and engraving of four or five plates ; making of a consolidated index ;
composition of the equivalent of about three or four pages of text ;
composition of consolidated index (about 48 pages) ; electrotyping
of new plates, new pages of text, and new index ; repaging of Parts
II to VI, both inclusive, and printing and binding of 1,000 copies
of the complete work, the cover to have a pocket, a pencil tube, and
a broad flap folding over the back. The manuscript of a proposed
introduction and list of authorities is inclosed.
5. The matter in the six parts as now published is electrotyped ;
the electrotype plates are at the Government Printing Office. The
expense of drawing and engraving the new plates, of preparing the
new matter, and of making the consolidated index would be charge-
able to the appropriation carried by the Army appropriation act
approved June 12, 1906, " For pontoon material, tools, instruments,
and supplies required for use in the engineer equipment of troops,
including the purchase and preparation of engineer manuals," or
which there is an available balance sufficient for the purpose ; the
expense of composition, electrotyping, repaging existing electrotype
plates, and of printing and binding to be borne by the appropriation
lor public printing and binding. The paper for the work is on hand
in this office.
6. I have the honor to recommend that 1,000 copies of the revised
edition of the six parts of the Engineer Field Manual, as hereinbefore
described, and their accompanying plates be printed at the Govern-
ment Printing Office and furnished f©r ike use of this office on the
usual requisition, the cost to be paid as stated in the preceding
paragraph.
7. A copy of each of the parts as published Is submitted herewith.
Very respectfully,
A. Mackenzie,
Brig, Gen., Chief of Engineers, U, 8, Army.
4
ENGINEER FIELD MANUAL.
INTRODUCTION.
In April, 1899, the Chief of Engineers directed the commandant of
the Engineer School to enter upon the preparation of an Engineer
Field Manual. At the same time all officers of the Engineer Corps
who bad been in the field during the Spanish War were invited to
contribute data and suggestions, and many of them did so. At the
Engineer School the worJ^ of compilation was committed to the
Instructor in civil engineering, then Capt. Henry Jervey» and under
his control, and mostly by his own hand, a general plan of a manual
was worked out, manuscript and plates prepared on the subjects of
reconnaissance and bridges, and more or less complete notes on roads
and railroads.
The Instructions of the Chief of Engineers required a topical
division and publication by parts, as completed. The part on recon-
naissance was published In tentative form and distributed to officers
of Engineers and other arms and to a few civil engineers, for com-
ment and criticism. The parts on bridges and roads were sent in
manuscript to certain Engineer officers for like criticism. As a
result, the method of treatment of subject-matter and the mechanical
features of the book were definitely determined and it was decided
to revise the work already done to conform it to the modified plan
and to republish Part I.
At this stage, 1903, the pressure of work at the Engineer School
made it necessary to place this duty in other bands and it was de-
volved upon the commanding officer of the First Battalion of Engi-
neers, and shortly thereafter the relation of that officer to the
preparation of the manual was made personal, instead of ex officio,
and ail subsequent work has been by the same hand.
By July 1, 1906, six parts had been published — reconnaissance,
bridges, roads, railroads, field fortification, and animal transporta-
tion. These parts are now collected in a sii^e cover, with correc-
tions of errors which crept into the first edition and some additions
of new matter which baa become available since the flrat publication.
The most important of these additions, made by direction, of the
Chief of Stall, is the incorporation of the signs, etc., lor finished
maps, published by authority of the Secretary of War in 1904. A
few minor changes which have been approved will be noted.
The opportunity now first offers to make acknowledgement of
sources from which mj^t^riaX has been drawn and of assistance
rendered by persons in the preparation and publicatJU>n of the
manual.
As to authorities, a list is appended of works wbicli have been
consulted and from which facts or suggestions have been derived.
Other works have been consulted, but nothing having been taken
from or suggested by them, they are not mentioned. Th^ titles In
the list which appear in full-face type have been relied upon, more
or less, as standard and as guides to topics and arrangement. But
a single work seems to deserve further mention, and that is tb'^
5
^ SHeraXSR FI£IJ> KANTTAL.
tnoomi>*wiW« Trantwlne, the indebtedness to which Is too obvious
^o r««uire mention, but too important to permit it to be dispensed
Il|*»r^ Sub$t«ntiAlly no matter from any source is quoted. The
J.j^nor of space required everything used to be rewritten with a
x-i^K- t^ condensation. In addition to the works cited, much valu-
Zui^ infoTVOition^ e«&pecially as to railroads and field fortifications,
i*^ obtained ftv^m tne reports of military observers with the Japa-
jrn^ Mild Russian Armies and from fugitive publications as to the
«'^r In Manchuria. Of the latter, the Journal of the Eoyal Engi-
»^V« <*^ Great Britain deserves special mention.
■^ j<*^^.^\nsil assistance in the preparation of text has come exclusively
#v«^t%% brt>ther oKttcers of the Corps of ESnglneers, with the single ex-
lIv^*Vt*^ii <^t " Landscape sketching," paragraph 85, and plates 39 and
S^ *» Reconnaissance.** which was abstracted from material fur-
« -t%<Hl ^>f Prof. C. W. Lamed of the Military Academy. In verifying,
**'^^^^t^,tn]p:, and correcting the work of the compiler, many omcers
J^**'*^^ r^^ndered assistance in greater or less degree, and none who
J^*^X^ li«%d opiwrtunity to assist have refused. But a few have given
•***^ZL^|<»|| of time ana lalwr as to make mention by name an act of
<^* . L^l^ justice. Lieut. Col. Abbot, who has handled the manual in
«* *J** o(n<^^ *>' *^^ Chief of Engineers during the entire period of
t»j2^^,^-^r«tUm and publication, has contributed never-failing enthusl-
P*^J «s|icouragiMuent, and counsel, which have been of the greatest
t^'***^'^!^!^ assistance. Maj. Rees read critically the parts on recon-
^*^^i'^.^rtm*t». brldcea. and roads. Maj. Sibert and Lieuts. Johnston and
^*«*j^|.|mtf did the same for railroads. Capt, Connor read the same
S|**J* ^xi<i forwarded a paper of his own on the subject, from which
|*«*Y^» «iWtfK<^»<tlons were taken. Maj. Gaillard read the parts on field
^k^'^^^^litoatl^^u and animal transportation and made valuable sugges-
<»^^^V||%oatl^»u and anl
C^'^^'rL frt>m personal
t'**'*'" i men of the Second Battalion of Engineers, under the super-
^^'^ t »n <*' ^"J* Jw^^on, instructor of military engineering at the
v*'***lu»*er School. The names of these men unfortunately have not
K***v nu^dP ot record. These drawings were revised and those for
^**^'^ Jrt 111 and VI made by Sergt. Pihlgrem, of the First Battalion of
r»* * ,1 ,n»crfl, aBHlstod for a short time by Corp. Plugel of the same or-
Vi»*>Y^rttlon, The drawings for Parts IV and V and the Addenda
li***i*% made by Mr. S. P. HoUlngsworth, of Washington, D. C. The
>v«V^^lug, partial and consolidated, was done by Mr. G. T. Ritchie of
Uu**'-, jiirary of Congress. Mr. Pickering Dodge, chief clerk. United
^^'^♦A* Knglneer Office. Washington, D. C, contributed valuable
Ht«*.Vj|nnce in final proof reading.
LIST OF BOOKS CONSULTED.
w ^rr and Practice of Surveying. Johnson.
T^^?l^Ty Toposraphy and Sketeblngr-
^^« «A« and Formnlne. Lee.
Tf J»' r Surveying. Gillespie,
mgfter Railroads. Gillespie.
Rt^f-jjer^n Poclcetboolc. Trautwlne.
K^f Bridffe ESaulpagre and Pontom DrI
W'lHfary Bridges. Haupt
W*"^l and Pavement*. Baker.
'^^ «rtry Con»trnotion. Baker.
Hf ?.^av Construction. Byrne.
ffii^Imle Railroad Location. Wellington.
^""^ >«d Con«trnctlon* Webb.
Root.
.n Track* Camp.
Curves. Allen.
nrxRODTTCTiozr. 7
The Railroad Spiral. Searles.
The Roadmaater'a Aaalatant. Railroad Gasette.
liocomotlve Brealcdo^vna. Enterffenclea, and their Rem-
ediea. Fowler.
Text-book on Locomotives. International Correspondence Schools.
Train Rnlea and Train Dlapatchlns. Dalby.
Block Signal Operation. Derr.
Letters of an Old Railway Of&cial. Hine.
Manaal of Field Kngrineeringr* Beach.
Pleld Fortification. Fiebeger.
Manaal of Military Bnfflneerlnff. Ernst.
Attack of Fortified Places. Mercur.
Royal Engineers Aide Memoire.
Handbook of Modern Explosives. Eissler.
Woolwich Text-book, Parts I and II.
Chatham Text-book, Parts II and III.
Text-book of Field ESnslneerlnff. Phillips.
Field Fortilication. Hutchinson.
British Manual of Field Engineering. 1903.
Destruction of Obstacles in Campaign. Bornecque, Tr. Burr.
U. S. Field Service Reffnlationa.
Manual of the Quartermaster's Department, U. S. Army.
Horses, Saddles, and Bridles. Carter.
Packer'a Manual. Daly.
Treatise on Feeding and Training of Mules. Riley.
Military Transport. Furse.
PART I.
RECONNAISSANCE.
PART I— RECONNAISSANCE.
1. TopoflTvaplilcal reeonitalssancey as here treated, covers the
instruments and methods necessary for the production of maps of
SMALLi ARKAS and routes of travel of sufficient accuracy for tem-
porary military needs.
No reconnaissance sketch or combination of sketches can be expected
to cover with sufficient accuracy an area of more than about 2 miles
on a side. Areas up to 10 miles on a side can be satisfactorily
mapped for military purposes by running transit or plane table con-
trol traverse lines which will locate some landmark in each square
mile, adjusting the traverses, plotting the adjusted traverses, and
then filling in the control skeleton thus obtained by sketching.
For larger areas triangulation or traverse control of greater ac-
curacy is necessary and the curvature of the earth soon becomes a
factor. No map of an area over 10 miles on a side should be under-
taken without a thorough knowledge of the best modern practice in
topographic mapping such as that followed by the United States
Geological Survey.
2. The information to be obtained In a topographical reconnaissance
may be grouped under the headings of time, cover, resources, and
nomenclature. The map should permit a determination of the
time which a column will require to pass between any two given
points by ishowing the distance between them and the condition of
the road or country which must be traversed, as regards its effect on
the rate of march ; the accidents of ground which will afford cover
to the army or to the enemy; the location, quantity, and quality of
water, fuel, grass, etc., and should give to each feature its local name.
The last requirement is of great importance and is the one most often
neelected.
S. Tlte fundamental topoirraphical operation is the deter-
mination of the direction and distance of one point from another
point.
The direction of one point from another is composed of two ele-
ments : First, the angle made by the line joining the two points, with
a vertical plane passing through one of them. This angle is measured
in a horizontal plane and is called the astmnthj second, the angle
made by the line joining the two points, with a horizontal plane pass-
ing through one of them. This angle is measured in a vertical plane
passing tfirou^ both points, and for convenience will be called the
4. Asimntlia^-^As an infinite number of vertical planes may pass
throngb a given point, it is necessary to select one as the origin of
azimuths. In topographical reconnaissance the plane selected is that
of tlie magnetic meridian at the point. Its direction in a horizontal
plane Is the line of rest of a freely suspended and balanced magnetic
needle, and this line is the origin of asimuths.
From this origin azimuths are measured in degrees of arc from O
to 300, passing from the north point through the east, south, and
west to north again. Azimuths, of 0* to 90*^ are ia the northeast or
11
|» XKOXHSSE FIELD MANUAL.
flviit quaUr«nt (f\£, 1) : thoae of 90^ to 180*" are in the southeast or
Mv v-ioia QUttilrant ; those from 180** to 270" in the southwest or
tbuU ^uaUruut. and those from 270** to 360** in the northwest or
^vuiih ^uailraut.
A^Uuuths are bearings between stations taken in the direction of
uv<vgioH!i of the reconnaissance. Bearings taken in the other direc-
lluu ur«> called back aalmiatlis. If the stations are numbered in
tUi'k oixU'r they are occupied* a bearing from a lower to a higher
uuutben'd Ktatlon Is an azimuth, and a bearing from a higher to a
Wwt'r uumbei'^d station it a back azimuth.
TUo method of stating aKlmnths described above is that commonly
U«^l U\ Hurveylng when direction is maintained by carrylnar an
ii«lmutli« It la the simplest to understand and use, and permits the
auglu between any two lines to be read at a glance.
Thi^re are other ways of axpr«8sing aKimuths, adapted to special
iHkuUUUak4 or cli'vumstances. In astronomical work and tables the
aviuuuh It) reckoned from the flootliy through W., N., and £., 360** to
Kouth ugaiu. Any astronomical azimuth differs from the corre-
»l>ou^lng aurvey azimuth by 180**.
iu uavi)£atlou azimuths are reckoned from the mariner'a com-
|iH«ii« Aud are called bearinss. The dial is divided into 32
l^uliitH ftnd each point into anarter points. The names of the
LuUuU and their relation to survey azimuths are shown In figure 1.
taud Hurveyors reckon bearings in both directions from N. and S.
Their coiupaHses are graduated 90° in each direction from the N.
auil S. points and a bearing is stated by giving the angle and
diiHH'tlou from N. or S., whichever may be nearest, as N. 46"* W., S.
formerly such bearings were reckoned from the nearest cardinal
Mulut, N., S., 10., or W., as W. 40** N.. which corresponds to N. 46**
W. This method Is very convenient for giving directions in orders
and reports. It is shown in the middle circle of figure 1.
5. A wpeclal method of azimuth measurement has been adopted for
uae lu the fire control of field artillery. The unit, called a mil. Is the
arc whose length is one one-thousandth of the radius. By computa-
tion this arc is 3'. 437 + . This length is not commensurate with the
length of the circle being Contained In it 6,283.24 times. For con>
vt^nlence of graduation, the circle is divided into 6,400 equal parts,
ausumed to be mils, the angular value of each of which is 3'. .^75,
differing from the computed value by nearly 2 per cent, which error
enters into all determinations and Is neglected.
Kach change of 1 mil in azimuth corresponds to a change in posi-
tion In a direction perpendicular to the line of sight of one one-
thousandth of the range. This method reduces all elements of fire
control to functions of the range.
6. The compasa is the standard instrument for the determination
of azimuths in topographical reconnaissance. It consists of caae,
needle, oofd, pivot, and atop, figures 2 and 3.
The card may be llaLcd to the case or moT-able, attached to the
needle and revolving with it. The stop raises the needle from the
givot and clamps it against the glass cover. A good compass must
ave a needle sufiiciently magnetized to settle accurately attd a pivot
free from rust and roughness. If the needle becomes too weak^ it may
be reraagnetized by rubbing gently from pivot to point on a perma-
nent or electro magnet, each end of the needle to be rubbed on the
pole which attracts it. In returning the needle for another stroke
carry it a foot or more from the magnet. The pivot may be polished
with Putz pomade or similar Bubstances on a soft stick.
If possible, however, tusn in the defective cempafls and get a good
— ~- \jx place of it.
needle loses part of its magnetism if kept for a long tipe oat of
ane of the magnetic meridian. In atorhig a coaipasB eare
be taken to place it in the case or on the shelf with the N.
its needle pointing nbrth.
KBCOmrAISBAKCZ.
LI -7
— i±.:tEL ■ ::ai»*,
•* » "^ ;r.i
1 1 in*i
«^^t. *«*
, *•-« 'niL^ t -*» Hfci»c isak isi*
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uj H«i£iii^ 'U tt* -utei* n wont aty^
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- «4»i »r • *» oa»ii«fr in dtf«lli»ti^ from place
iSr^oXa ti ^-'^c -«*ttipi ttt « aingfe day's
BECOHHAISSAVCS. 16
Abnormal deflections of the needle, due to local disturbances,
are sudden and erratic and should not be distributed among all the
courses, but only among those in which there is reason to beiiere the
disturbance occurs.
A simple way to detect — not measure — such disturbances is to take
frequent back azimuths. If the position of the needle is normal at
both stations, the azimuths and back azimuth will differ by 180**. If
there is local attraction on the course, it will usually be stronger or
cause a greater deflection at one station than at the other, and the
azimuth and back azimuth will not differ by 180°.
Another way is, when taking the bearing to a station, to select a
well-defined point beyond and on the same course. On arriving at the
new station, take a bearing from there to the selected point ahead.
If it is- the same as the first bearing to that point, there probably is
no local disturbance. If the two bearings to the same point differ,
there probably is local disturbance.
A course in which local attraction is detected or suspected should
be noted, and if, on closing, an azimuth correction is necessary, it
should be applied to the suspected courses.
10. Gradients. — ^There can be but one horizontal plane through a
given point, and it may be determined by the spirit level or plumb line
without serious error. Gradients are measured by taking the angle of
the line of direction with a horizontal line through the point.
11. Gradients are commonly called grades or slopes and are ex-
pressed in degrees, as 1°, 2", 31°, 6V slope, etc.
Each angle corresponds to two slopes, one up and one down from
the initial point. Rising grades may be recorded with a + before, or
an B after the number of degrees ; falling grades with — before, or F
after. On a map, general slopes are indicated by an arrow pointing in
the direction of the drainage, with the gradient written beside it,
thus >. Road grades are indicated by an arrowhead at
top and bottom of the grade, the one at top pointing toward the road
and the one at bottom away from it, thus i . •
Gradients are also expressed by the relation between the change of
elevation-^rise or fall — ^and the corresponding horizontal distance.
This relation is stated in various ways.
By the rise in feet per 100 feet horizon or the foot rise as a per-
centage, as " the slope is 4 in 100, or 4 per cent."
By the foot rise for 1 mile of horizontal distance; as "the grade
is 50 feet," or "a 50-foot grade." This method and the preceding
are commonly used for railroad track grades.
By the number of feet horizontal corresponding to 1 foot rise; as
8 to 1, 10 to 1. This method is commonly us^ for slopes of em-
bankments and excavations when less than 45**.
By the foot rise corresponding to 1 foot horizontal; as, 1 on 1.
6 on 1. This method is commonly used for slopes of embankments
and excavations, etc., from 45** to 75*.
By the number of inches horizontal corresponding to 1 foot rise;
as, 3 inches to the foot, 1 inch in the foot. This method is com-
monly used for gradients of 70" and over and is called hatter.
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IKBOOSVAISSAHCE. »
13. The clinometer is the instrument adopted for measuring
gradients, T^ith the horizontal plane indicated by a spirit level. It
consists (fig. 4) of a sight tube. A, with a graduated, vertical arc, B,
fastened to it, and a level tube, €, with attached index arm, D.
revolving about a horizontal axis through the center of the vertical
aim. The bJase of the sight tube is a plane parallel to the line of
sight. Under the center of the level tube is an opening in the sight
tube, inside of which is a mirror occupying one-half the width of
the sight tube and facing the eye end at an angle of 45° with the
line of sight. A horizontal wire extends across the middle of the
sight tube in front of the mirror. When the bubble is brought to
the center, its reflected image seen from the eye end appears to be
bisected by the wire.
The central position of the bubble Indicates that the level tube is
horizontal, and the reading of the Index arm upon the arc Is the
angle between the axis of the level tube and the line of sight. This
reading should be 0° when these lines are parallel. The vertical arc
is graduated each way from 0° at its middle point. The index arm
has a double vernier whose smallest reading is 10' of arc. Gradients
of more than 45** are difficult to measure on account of the fore-
shortening of the level tube as reflected in the mirror.
When the vernier is set at 0°, the instrument may be used as a
hand level to locate points at the same elevation as the eye. The
graduation on the inner edge of the vertical limb corresponas to the
ordinary fractional method of indicating slopes, as 1 on 2, 1 on 10,
etc. This scale should be read on the forward edge of the index
arm, or in some forms on a special index mark on a shorter part of
the arm.
The level tube la maiie parallel to the Blarht tabe by the
adjusting screws E (fig. 4). To test and correct the adjustment,
place the instrument on a smooth surface, the more nearly horizontal
the better, and mark carefully the position of one side and one end
of the sight tube. Center the bubble by moving the indivx arm, and
read the vernier. Reverse the instrument, bringing the other side
and end of the sight tube to the marks. Center the bubble by
moving the index arm, and read again. Note and record for each
reading its direction from 0", whether toward or away from the eye
end of the sight tube. Note and record also the location of the eye
end in each position with respect to some fixed object, so that the in-
strument can be replaced in the first position or second position at will.
If the first and second readings are the same, the adjustment is
correct. If they differ, take the mean of the two and set the vernier
at that reading on the side corresponding to the first reading. Place
the instrument in the first position and bring the bubble to the
center by means of the adjusting screws B. For a check, set the
same reading on the side corresponding to the second reading and
place the instrument in the second position. The bubble should
come to the middle.
The grwLyrlty clinometer adopted in 1906 is shown in figure 5.
It consists of a circular case in which is a graduated circle con-
trolled by a pendulum. The line of sight is through the peep L and
a glass-covered opening at M. The zero line is engraved on the glass.
A mirror near the center reflects the scale back to the peep. Looking
through the instrument the object is seen on tbe zero line, and at
one end of the latter a graduation of the scale is visible. The gradu-
ations are from zero at the horizontal each way to 45°, the gradua-
tions and numbers for elevation being in red and those for depression
\n black.
A sliding bar at JT unlocks the spring-controlled stop, which, when
pressed, frees the pendulum and graduated circle, and when released
stops them again.
To use, move the locking bar F to free the stop H ; hold the in-
Btrument in the left hand with the forefinger on the stop; depress
stop ; bring line of sigbt oA^^objecf and read.
94346*— 17 2
BBOOmSTMSSAKCS. 1^
A type of hand level designed for slope readings is now gen-
erally preferred to the ellnometer. This hand level has horizontal
lines on the object glass, either reading degrees or per cent. With
the per cent graduations it Is possible to obtain differences of eleva-
tion without the necessity of using tables of degrees for differences
of elevation, but the degree graduation is suited for use with the exr
isting scales of slopes, and is generally preferred.
14. The determinatloii of flrradlentB by tl&e plmitli line iB
quicker and simpler, but less precise than with the clinometer,
though exact enough for ordinary purposes. If a line of sight be
taken along the edge of a board and a line be drawn on the board
perpendicular to the sighting edge, this line, when the board is held
in a vertical plane, will make the same. angle with the plumb line
that the sighting edge makes with the horizontal, or, in other words*
will indicate the gradient (fig. 6.).
Such a construction is called a slope board and is readily im-
provised. The scale may be constructed by sweeping an arc of a
circle AB (fig. 6) from the point C, at the intersection of the per-
pendicular and the sighting edge. From the perpendicular at D
lay off each way on the arc chords equal in length to the radius CD
divided by 57.3« It is convenient to take a radius of 5.78 inches, or
5i inches scant, when the chords will be iV inch, or a radius of 7 A
inches, when the chords will be i inch, accordingly as the scale used
is graduated to tenths or eighths.
Short radial lines drawn at the ends of the chords form a gradu-
ation in degrees. The scale may be drawn on the lower edge of
the board by prolonging the radial lines as indicated in the figure.
The plumb line is suspended from the point G.
In use, the board is held so that the plumb line swings free but
very close to the board. The sighting edge is directed to the object
and when the line is steady the board is quickly tilted so that the
line draws across the edge. The board is then turned to a hori-
zontal position or nearly so, and the reading taken ; or, when' the
-line is steady, it may be pressed against the board with the finger
and held In place until the reading is taken. With a straight scale
and for steep grades the latter method is better.
15. Blevationa. — From the alope and distanee the elevation of
a point above an assumed plane of reference may be derived. The
dilleremee of helffbt of any two points is known by comparing
their elevations above a common plane^ called the plane oC reCer-
ence* or datnn&.
The plane of reference is taken low enough so that no point of the
area to be covered bv the reconnaissance will be below it. This makes
all elevations positive. Knowing the height of a point above this
Elane of reference, the elevation of any other point may be obtained
y taking the gradient and distance to that point, deriving from
them the dlfBerence of height between the two points, and adding this
difference to the elevation of the first point if the gradient is rising,
or subtracting it if the gradient is falling.
The elevation for a given gradient and distance depends upon
whether the distance is measured along the gradient or along the
harizontal. Distances paced are along the gradient. Those measured
with a chain will also usually be on the slope, though sometimes care
is taken to hold the chain horizontal, in which case the table for
horizontal distances is to be used. Those determined by intersections
or scaled from a map are along the horizontal.
The differences of elevation corresponding to various gradients and
any distances may be taken from the following tables :
EHQINSBE riELD KASnAL.
Tablb II.
DUTarauw of slrvBtlao (or he
02707
OT0I7
owrs
2«7I3
06125
09837
noes
aXTTi
22743
25477
»i239
01570
023SS
03141
09924
0*719
0787S
09459
12043
15SW
10130
23i3»
2&S0O
32757
303*3
40070
4389S
5i8«l
The dirferensp of elcTfttlon
MiKW mn; be obtalaed by n
tbe aDslu or gradient, Table
BSCOlTNAISSAlfCS.
31
Table III.
17.
Differences
of elevation
for gradients of 0"
and 30*
\ and
difltances measured on the slope.
.
Oradi-
. Difference of elevation for sloping distances of
— ^
entiii
de-
•
grees.
1
2
3
4
5
6
7
8
9
i
00087
00174
00262
00349
00436
00523
00611
00698
arm
1
00174
00349
00523
00898
00873
01047
01222
01396
01571
u
00262
00523
00785
01047
01309
01571
01832
02094
02356
2
00349
00698
01047
01396
01745
02094
02443
02792
03141
2i
00436
00872
01308
01745
02181
02617
03053
03489
03926
3
00523
01047
01570
02093
02617
03140
03663
04187
04710
4
00697
01395
02093
02790
03488
04185
04883
05580
06278
5
00871
01743
02615
03486
04358
05229
06101
06972
07844
6
01045
02090
03136
04181
05226
062T2
07317
08362
09407
7
01219
02437
03656
04876
06093
07312
08531
09740
10968
8
01392
02783
04175
05587
06959
08850
09742
11134
12626
9
01564
03129
04693
06257
07822
09386
109S0
12515
14079
10
01736
03473
05209
06946
08682
10419
12155
13892
15628
12
02079
04158
06237
08316
10396
12475
14564
16633
18712
14
02419
04838
07288
09677
12096
14515
10934
19854
21773
16
02756
05513
08269
11025
12361
13782
16538
19294
22U51
24807
IS
03090
061 SO
09270
15461
185il
'21631
24731
27811
20
03420
06840
10261
13681
17101
20521
28941
27362
3078»-
22
03746
07492
11238
14984
18730
22476
20222
20968
33714
24
04067
08135
12202
16269
20337
24404
28471
32539
36606
26
04384
08767
13161
17S35
21918
26302
30686
85070
30463
28
04605
09389
14084
18779
23473
28168
32863
37558
42252
30
05000
10000
15000
2000O
25000
30000
35000
40000
45000
Th« difference of elevation for any sloping distance and any angle
or gradient may be found by multiplying the distance by the «ine of
the angle, Table XIV.
Eixplanatlon of use of Tables II and III :
Rule. — From the line of the given gradient, take out the tabular
numbers corresponding to each of the figures of the given distance,
beginning at the right, and set them down ; each one place to the
left of the one above if. Retain the ciphers at the beginning of the
last tabular number taken out, if any. Other left-hand ciphers may
be dropped.
Add the tabular numbers, and point off from the left the number
of places equal to that of the left-hand figure of the distance,
counting any left-hand ciphers. The result is the difference of
elevation. In the same unit as the distance.
Bxamplea. — For the difference of elevation corresponding to a
gradient of 3** and a distance of 6,273 feet on the slope —
From Table III —
For 3 opp. 3* and under 3, 1570
For 7 opp. 3* and under 7, 3663
For 2 'opp. 3** and under 2, 1047
For 6 opp. 3" and under 6, 031 40 retain leading cipher.
As 6 is in 4th place, point off 4, 0328. 2900
Diff. of elevation >- 328. 29 ft.
88 ENGINEEK FIELD HAHUAi:.
2d. What difference of elevation for gradient of 5\ and horizontal
distance of 7,180.56 yards?
From Table II —
Opp. 5*" and under 6, 6250
Opp. 5° and under 5, 4375
Opp. 5* and under 8, 7000
Opp. 5" and under 1, 875
Opp. 5** and under 7* 06125 retain leading cipher.
7 is in 4th place, point off 4, 0628. 299000
Diff. of eleyatlon = 628. 299 yds.
18. Barometric levelingr* — The weight of the atmosphere at sea
level Is 14.703 pounds per square inch, equal to the weight of a
column of mercury 29.92 inches high, or a column of fresh water
84.7 feet high.
The aneroid barometer records the pressure of the atmosphere
in IncheSt the same as a mercurial barometer, .the reading being
taken from a pointer moving on a circular scale. The corresponding
elevation in feet is also shown on the dial of the aneroid barometer.
It must be carefully handled as it is sensitive to shocks. A screw
head will be seen through a hole in the back of the outer case by
which the needle may be brought to any desired reading, and the
instrument corrected whenever it can be compared with a standard.
With the aneroid, corrections for instrumental temperature can not
be made, and for this reason small pocket instruments are preferable;
as carried in the pocket they are not exposed to so great changes
in this respect.
The preasvre of the atmospliere irarieB with the altitude
above sea level, and it also varies with the moisture, temperature,
and latitude, which do not depend upon the altitude.
In measuring altitudes with the barometer these other causes of
Tariation must be eliminated so far as possible. It is best done by
simultaneous observatfon at both stations. If the stations are not
far apart all disurbing conditions will be substantially the same at
each and therefore eliminated, except temperature, which, with con-
siderable difference of altitude, will always be less at the upper than
at the lower station.
If 9imult(meou9 observations com, not be made, the stations should
be occupied with as little interval of time between as possible, and
better results will be obtained if the time of observation can be so
chosen as to take advantage of calm, bright, dry weather.
When the hygrometric conditions are very uniform an aneroid
read at Intervals on a day's march over a rough country will give
a fairly good idea of the profile.
BE00inrAI881JICB.
Dodltions and u
BBCOm-
Altitude
Difl.
BBTom-
Altitude
Dltt.
Baroc
0- Altitude
Dili.
above
Kr
reading.
sealeTBl.
0.01".
raKltag.
sea level.
0,01".
reldli
ig. sea level.
0.01".
fncAu.
Fat.
FiH.
Jnoko.
Fia.
Fett.
IlKkt
. JW,
Feti
18.0
^■^
-15,1
8,20)
Tt.
4 3,483
1
8,082
~ia.2
B 3380
W.3
3
u'.m
7,B«)
1 .2
A 3
377
1 .1
7 3
\k'n2
t!
:?
T,507
7,177
1 .0
37
8 I
973
11
7,388
a!o
3 !
i;;.'S»
7;iSl
3 :
570
10.0
7,004
470
o.a
688T
6 '.
0770
0.0
8,6M
J :
m
0538
m
0.8
n'.'m
0,423
1 '.s
s.g
u:.«s
:s
0308
2&
0 1
e,iM
m
»!o
eoso
m
n:is4
.1
5,887
iiS
III. -OS
.2
5,854
5, BIO
m
\\
S i
018
9.i
1(1:343
!»
r^^.
10 B
20
0 924
d.t
'j!'jn
25.0
4:968
id. 9
3 043
'j!h8
4 550
9.2
.3
4:«43
K.g
5 45S
0,»
l'!4M
4,535
10 7
0 306
0.2
1>..33
4,428
B,a
4,321
S 182
H
as
'.%
4^004
10 fl
116
10 5
30
0 OD
1 -01
»^1
X.0
3 809
2 -181
S-2
3,T94
m*
0.0
22
J
Is
a
■J
3>0
5 -451
"
u
ENGHrEXE PIEZiB XAHTTAL.
Table V.
20. Coeffllclei&ta for temperature correction. — ^Argument
(* + t')=Sum of temperatures at the two stations:
t+t'.
Coefficifint
C.
t+t'.
Coefficient
a
<+r.
Coefficient
a
9
0
-0.1024
o
60
-0.0380
9
120
+0.0262
10
—0.0915
70 .
-0.0273
130
+0.0368
ao
-a0806
80
-0.0166
140
+0.0472
30
-0.0608
90
-0.0058
ISO
+0.0575
40
-0.0592
100
+0.0049
160
+0.0677
60
-0.0486
110
+0.0156
170
+0.0779
60
-0.0380
120
+0.0262
180
+0.0879
Sxamples:
Station.
Sacramento.
Summit
Temper-
ature.
42.1
From table of elevations Sacramento — — 12. 7
Summit «= 6,901.0
t+t' - 102*
.-. C - +0.0070
.*. Temperature correction, 6,913.7 X 0.007
Biff. = 6,913.7
= +48.4
■
H
= 6,962.1 feet.
Station.
Barome-
ter.
Temper-
ature.
Ticwer
•
•
Inchet.
28.076
22.476
57.3
^DDer
3S.5
From table of elevations Lower
Upper
Dili.
t^t' « 96'».08
... c - +0.0004
.'. Temi)erature correction, 6,060 X 0.0004
7,867.0
1,807.0
6,060.0
+2.4
H - 6,062. 4 feet.
21. Use of compasses. — A good needle requires time to settle even
when the case is firmly supported, and the user should cultivate the
knack of catching it at the middle of its swing, which is the desired
reading. If the compass can be supported, it is always better to do
so. Then the sight can be carefully taken and the position of the
BBCONSAISSAKCE. 8ft
eye changed to read the needle. Wait till the swing gets down to
4^ or 5**, which It will usually do in a few seconds. Then catch the
highest and the lowest readings on the same swing and take their
mean for the true reading. If the first swings are very large, catch
the needle with the stop near the middle of the swing and release
it quickly. This will suddenly check the swings and shorten the time
in which the readings can foe taken.
In using the box compass without a support hold it sufficiently below
the eye, so that the swing of the needle can be seen. Point tne edge
of the lid in the required direction, catch the needle with the stop
in the middle of a swing and hold it stopped until the reading is
taken. Stop readings are less accurate ^an sight readings, as the
needle may be displaced slightly when off the pivot. When the stop
is used press it quickly and firmly. Always sight a fixed-card compass
from the south end of the card afld read the north end of the needle.
With the prismatic compass the stop is not used except to check the
tfwings. Utilize a support if practicable. The prism having been
adjusted for focus, as already explained <par. 8), adjust the case so
as to bring the scale into focus, and when the swings become small
read the extremes and. take the mean.
Compasses for night marching are on the inaxket, but are not very
reliable. They have the dial rendered luminous by a paint. After
exposure to the sun or strong daylight they give off light, at first
rather strong, but rapidly diminishing in intensity. After a few
hours they are not bright enough to be of much use.
The surest preparation for night marching is a provision for
Illuminating the compass by oc/dinary means without allowing the
light to be seen.
22. T6 determine the de^llnatiott of the compass s
First method; from flte 8un. — Prick a small hole in a piece of tin
or opaque paper and fix securely over the south edge of a table or
other surface perfectly level, so that the sunlight coming through
the hole will fall on a convenient place on the surface (fig. 9). The
hole may be 2 fleet above the table for long days and X8 inches for
short ones. Half an hour before to half an hour after noon mark
the position of the spot of sunlight on the horizontal surface at
equal time intervals of about 10 minute^. Draw a curve as bd
(fig. 9), through the points marked, and from point c in the hori-
zontal surface and in a vertical line with the kole a sweep an arc
ej intersecting bd in two points. The Hne eg, drawn from c through
a point on the arc midway between the intersection, is the true
meridian. The line bd illustrates the method merely, its form varies
with the sun's declination.
Second method; from the sun or a star. — -Observe the magnetic
bearing of the sun, a planet, or a bright star at rising and setting on
the same day, or at setting on one day and at rising on the next.
Take the difference between the sum of tne rising and setting azimuths
and 360°. One-half of this difference is the declination of the compass
or variation of the needle, east if the sum of the azimuths is less
than 360** ; west, if it is greater. In nslngr this method, the ob-
servations are better taken when the object Is just above the true
horizon, or at a gradient of zero. This can usually be done if a high
point is chosen for the observations. If it ean not he done, be care-
ful to take both observations with the object at the same gradient.
This is most important irith the san. Under the least favor-
able conditions an Inequality of 1° in the gradients at the times of
observation on the sun may introduce an error of i** In the result. If
nsins a star, choose one which rises nearly east from the point of
observation, and the inequality of a degree in gradients will not be
material.
The change in declination of the sun between observations can not
affect the result more than i°.
Both observations need not be made at the same point, but should
not be more than 10 miles apart in east and west or north and south
directions.
r
36
ENOZNEEB VIILD JCANTTAL.
<'>,:
Of
0
E
"^^
°/.:5>..
Slg.ll
BMP
0
BECaKKAISSAHCE.
27
The two foregoing methods are applicable in the fiorthem' or aouth-
em hemisphere.
Third method; from Polaris, — The true north pole is abont 1** 12'
distant from Polaris on a line Joining that star with one in the
handle of the dipper, and another in Cassiopeia's Chair (fig. 10).
One of these stars can be seen whenever Polaris is Tisible. The
Folar distance of Polaris is decreasing at the rate of 19'' a year,
t also varies during the year by as much as 1'. The latter variation
mav be neglected, and the former also for a series of years.
Imagine Polaris to be the center of a clock dial, with the line
Joining 12 and 6 o'clock vertical and with the position of one df the
lines described considered as the honr hand of the clock. The dis-
tance in Bsimuth of Polaris from the true north may be taken from
the following table :
Tablb VI.
23. Table aliovvlns tlie aalmutlfta of Polaris in different posi-
tions with respect to the pole. Epoch 1011 ; polar distance 70'.
Latitude 0** to 18" north. This table may be used until 1930.
Clock reading of —
Ari-
muth
of
Polar-
is.
Clock reading of—
Admuth
of
Polaris.
Clock reading of—
Azi-
of
Polaris.
1
Cass.
Z
TJrsae
Mai.
8
Cass.
z
Ursae
MaJ,
a
Cass.
Z
Ursae
MaJ.
XII:30
I
1:30
II
III
iin
viao
vn
viiao
vni
IX
X
18
85
49
61
70
61
IIII-^
V
V:30
VI:80
VII
VII ao
xao
XI
XI:30
XII :30
I
1:30
0 /
49
35
18
359 42
359 25
359 11
VllI
IX
X
X:30
XI
XI:30
II
III
nil
1111:30
V
V:30
0 /
358 59
358 50
358 59
359 11
359 25
359 42
For higher latitudes add to the small azinraths or subtract from the large ones, as
follows:
Lat. 19«-30% A. Lat. 51 •-53% V„.
Lat. 31 ^-S?', A. Lat. 56°-67% A-
Lat. 38"-42% A. Lat. 58''-59% ^%.
Lat. 43'*-46', A. Lat. 60*»-6I \ ^.
Lat. 47«-50% A.
It is well to keep track of the position of Polaris by noting it fre-
quently and taking the corresponding clock time. Then if on a
cloudy night a glimpse of Polaris is had, the observation may be
taken even though the other stars can not be seen.
24. For practical details of tlie observation, the following
may serve as a guide: Select a clear space of level ground not too
near buildings or any object which might cause local disturbance of
the needle. Drive a picket, leaving its top smooth and level, about
18 inches above the ground. Six feet north of the picket suspend
a plamb line from a point high enough so that Polaris, seen from
the top of the picket, will be near the top of the line (fig. 11).
The line should be hard and smooth, about -^ inch diameter. The
weight at the bottom of the line should hang in a vessel of water
or in a hole dug in the ground to lessen its vibration. Drive a
second picket in range with the first one and the plumb line a short
distance north of the latter. Make a peep sight by punching a hole
aboor ^ Inch dtsmetpr in a pieo> of paper and hold it oa the tx»
of thp flr^t picker: adjast it ^o rhar die sirar is behted the pioaip
line vrben looking rhrom^ rhe peep. Note the ponltion of one of the
.>4rar9 on tlie imai^liiary clock fttce at the mcmipnt the observatiiM is
Mk^n. Mark fhe poaLtioa of the peep oa the top of the ftrst pifcket
aniY I^y a straishredse or atrptch a line from that point tfMiehiBa the
plomb Mnt- to thf^ second picket. Place tbf north- aiid-«Miith edge of
fhe compasw box asrainnr rhe lint^ or i«rrai£hr(Mi)se and read the needle
Find the azbnnrb oi the star at the time oi. oteervntian frmn
Talvl** VI.
It the as. mft ^mWmrim (Table TI» and the — n<t»i: •€ tke
iw«dl« ar(> b«>th le«n or l^miUt gaaateM than 180^. tteir ^tfl. is
the deefiamttoBf c«»t If the meedle reading Is If—. ^r«at if it is
ST venter. If one of these quantities i» !««■ and the otlter svcAter
than 180*, add .'^60'* to the less*»r and take the difT. which is the
declination ; enat If after the addition is made the mee^le rending is
]ei»«9 ^rest if it is fpre«ter than the taboiated ax.
This m*^thod wiTI afre rp^nlt.^ trne to wfthin I".
^5. IMstnnee« pa^ssed over are ordinarily measnred by the stride
of a man or a hor^A. or by rhe r*»voltitiona of a wheel. IMstanees not
pSAfl^d over are determinpd by icte-rsection or are estimated.
PnelnjK on foot« — The len^h of a man's p«ce at a natural walk
Is atK>nt Zf> Inrhf'S. varying somewhat above and below. A stride
equals two paces. Each sketcher must determine his own length of
pace by wnlkinii; several times over a known distance. An unnatural
stride should never be taken. Knowing the length of a pace or step,
the measnrement of a distance is only a matter of counting steps!
The counting may be done mentally, and with practice becomes a
subconscious operation, leaving the attention free to take note of sur-
rounding objects and conditions. The greatest danger is of drop-
ping 100 paces. It Is better to keep a tally of the hundreds. By use
of a paee imlly all danger of error is avoided.
On level ground careful pacing will give distances correct to 3
per cent or less. The normal length of pace decreases on slopes.
Tlie decrease varies with the slope and with the direction* whether
ascending or d«>sccndlng. The following table gives the length of
fmce on slopes of 6^ to 80*, corresponding to a normal pace on a
eve I of 80.4 Inches.
Tabi«b YII.
Slopes.
TiSnKth of fltpp asoondlne. .
Leiiglti of step descendint;.
0'
30.4
30.4
5'
10«
15"
20"
19.7
26.4
25"
27.6
20.2
24.4
28.3
22.1
27.6
17.8
23.6
30*
15.0
19.7
Tor the jinme person, the length of step usually decreases with
fiitlgup. Hkcytclinrs stionld tost their pace when fresh and when tired,
nud If llUMo Is an nppreclnble difference, use one length tor the morn-
ing Hitd till' olhoi' length for the afternoon work.
20 A dlf^lnnco on n slope measured by foot pacing may be reduced
to the cot'i'ot't horlfontnl distance for plotting on the map by the
fnlhm'Ing tnlile. which takes account of the decrease In length of
i)H('e, Tublo VI T, and also of the reduction to the horizontal. Table
All. ThiR tnblp Ortu be used only when the length of pace has been
di*tei'nilned on level ground, which should usually be done. ¥^en a
cotiRtdornble stretch of road la found with fairly uniform slopes, a
spoolHl nvernge rntlng may be made over a distance involving a
•ali'ly rei>resotitntlve rnnge of slopes and this average rating mdy be
iBei! without Induction.
iiscoirHAXSSAjrcB.
bfl
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s
etc
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©a
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o
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ft
Pi
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p4
ft
■^Udt«>aOOi~lC4«tf<iOtvOOOtOO«4«WO«
^?d^S5c4b:c4i>:cJ5Je2^»ot^«5o5-;c4
00 -^l* O lO ^ r> CO 0» «(« O CO "^t 09 O 00 «0 •«!• C4
u} 0» C9 «9 Q C9 1>« 9 '^ oo i-i t^ C9 o» ^ oce c4
8s;
l8SSSfe2;S 55551
C4 000t^iOCOi-HOsQOcD'of<«OQCOC4-^cOX
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a»^ OQ C» go M OC COOC Ob 00 t«> ^ U3 ^ C>9 M <-<
O O O O O O O O O O O r-l *>i ^ ?l CO CO '^
aoa»oo*-ie<4coi-<«<'««<tocp'<4<e<iiooocoTt<cs
00 t^ CO Tf CO « f-f O QQ>- cp "^ e* O PO « "«J< CI
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O O f-4 T^ *^ 1-4 T-l i-H r-4 rH i-H Cl CO <^ *0 <0 CO r»
00 C^ C« 4-1 O O A 00 !«• Ni CQ C» e<l ao QO tH ««« t»
t* gi £2 ^ t* 'ff ^ t^ S* »^ od t^ i»i cd »(5 « ■'rf CO
u^oooo1-)co■^co^«aaoM^ou^ou>ou3
i-5»-5^o3cx5i^«rfui'^coc»5^c^t^o5c5c<l(pi
8oO'-ic><w«»<iocDt^o0^.e5iO"^^cQe3
^«•cO"^coe>^1-HO»oot*«o■<*<»-4oo^oc^o»cD^^
od«'*c4c5ot5u5M»-<^t^«dTi*^cioo5o^
oo<
J?5
CO CO^ 1
g
coot>-ooooTt(o»0'-<coe^oo-^©coc>iooTt<
SO»-HC'lC0'<TU*>COt--00»0000t*-Fj«CpcS
i-HT-t^i-li-ti-li-ti-ti-Sf-tNcC-^"5®t^00
^
^■*-^»O?OCD«Ot>.JC^Q0 0QM«© 0'<*<00 0»eO
®o»^CTeo<*»occ't*o5t«.co«0'^c*^c^f-(
Oi-t'-t'-^i-Hi-ti-t»-t»-«i^C>iCC'^»OCOt^00
• ■••••■•tttltCtfll
• ••••■•••••••■••■»
80 ENaiNZXR XTELD MASHJAL.
Table VIII gives directly the horizontal equivalents of the distances
usually occurring in foot pacing. If desired, other distances may be
obtained by combinations.
From 1 to 9, take the first figure, left-hand cipher Included, of 100
to 900 for the whole number and the second figure for the tenths.
From 10 to 90, take the first two figures, left-hand ciphers included,
of 100 to 900 for the whole number and the third figure for tenths.
For 290 take 100 + 190 ; for 440 take 140 + 300, etc.
Example : For the horizontal equivalent of 738 paces on a 5* rising
slope.
700 + 30-1- 8—632.8 + 27.1 + 7.2=667.1.
28. Pacing moiinted. — The average tcalk of a horse is a mile in
16 minutes, or Si miles per hour, making 120 steps, covering 110 yards
per minute, the step being 0.916 of a yard, or 33 Inches.
The average trot is a mile in 8 minutes, or 7i miles an hour, mak-
ing 180 steps, covering 220 yards per minute, the length of step being
1.22 yards, or 44 inches.
It will arenerally be foiind more con-venlent in pacing, both
on foot and mounted, to count the steps of one foot only, and multiply
the number counted by the stride of one foot, which is twice the
length of step given above. In this case the number counted is
doubled for use with the tables and scales given herein.
Tlntliiflr. — Counting the steps of a horse diverts the attention more
than is desirable, andf it is better to determine distances in mounted
reconnaissance from the times occupied bv the horse in passing over
them. A stop watch is the most satisfactory timer for this pui^
pose. The rating is done by ascertaining the time required to pasa
over a known distance. Time and step ratings should be taken
together by counting and timing at once. Ratings should be taken
before the reconnaissance, if possible, but for short stretches of hasty
work the averages given above may be used without serious error.
Horses travel better in pairs, and two men should be sent 6ut to-
gether, one to do the sketching and the other to give his entire atten-
tion to taking the time and keeping his horse at a regular gait. It is
better to rate the pairs together. If it has not been done, take the
rate of the timer's horse.
When a sketcher is traveling with a party and must keep their gait,
an occasional count of his horse's steps for a minute or two will give
a special scale for use in plotting.
29. The speed of a horse over road grades, even in moderately
hilly countries, is not affected by the slope sufficiently to make an
allowance necessary. Distances up and down grades measured by
timing in mounted reconnaiFsance will require no correction except
that to the horizontal, Table XII, which may be applied if the slopes
exceed 5** or 6°. This statement does not apply to distances
measured by mounted pacing or counting the steps of a horse.
30. The walk Is tbe normal aralt for reconnaissance. — If
greater speed is necessary, the timer may go on while the sketcher is
taking angles and plotting, the latter taking the trot or the gallop and
overtaking the. timer Just before he reaches the next station. This
method should be used only when the required distance can not be
covered at a walk.
If circumstances require short distances to be covered at a trot or
gallop, the times may be reduced to walking time by multiplying by 2
for the trot and 3 for the gallop.
31. The odometer is an instrument for recording the number of
revolutions of a wheel. The adopted form is in a leather case, 4i
inches in diameter by 21 inches thick (figs. 7 and 8). It is attached
by straps to the front wheel of a wagon (fig. 7). To read, the case is
opened, the registering train withdrawn, and the number of revolu-
The bearings of the odometer must be kept free from grit and may
oiled with fine oil used sparingly ; gummy oils or grease mnst not
BXCOSHAISSAirOE. SI
be used. If good oil is not to be had, rub the bearings with a soft lead
pencil*
Odometer readings are valuable as a rough check on a day's march.
They are not accurate, but are free from large errors. Two instru-
ments on the same wagon will not always agree. On heavy roads,
mud or sand, there is a slip, sometimes positive and sometimes nega-
tive.
Table IX.
32. Ifnmber of revoliitioiia per mile, of odometem attached
to wheels 36 inches to 48 inches diameter :
Diameter of wheel. Revolutions.
36 Inches . 560. 2
37 inches ..— ^ 545. 1
38 inches 530. 7
39 inches 517. 1
40 inches 504. 2
41 Inches - 491. 1
42 inches 480. 2
43 Inches 469. 0
44 inches 458. 4
45 inches 448.2
46 inches * 488.4
47 inches 429. 1
48 Inches 420. 2
Sise of irlieela of some military wagons : Ambulance, 36| inches ;
ponton (light) tool and chess, 42g inches; escort, 44} inches; ponton
(heavy), 45 inches; Army six, 47| inches.
33. BatlmatloB of dlataneea is a knack which may be culti-
vated by practice to a degree of accuracy far beyond that whidh is at
first attainable, and quite sufficient for the location of many objects
cflT the traverse line. Short distances are more closely estimated than
longer ones ; those on a level, than those up or down hill. When the
Intermediate ground can be seen, the estimation will be closer than
when it can not.
A rough estimate ist distance may be made from the velocity of
sound, as 1^ knowing the time that elapses betweai seeing and hear-
ing the discharge of a gun, or the fall of an ax. Note the time in
seconds nnd multiply by 400 for the distance in yards.
Distances across water are usually underestiinated. The distance
of the visible horizon on water in miles is 1.225 ifH; H being the
height of the observer above the water surface in feet.
A cartridge or other small heavy object fastened to a string 10
Inches long and allowed to swing throught a small angle or are will
beat half seconds approximately.
34. Tlfte location of a point by Intersection is done by
taking azimuths to it from two known points. As each of these
azimuths when plotted must pass through the unknown point, it
mast be at their intersection.
An observer at an nnkno'wn point may locate himself from
two visible known points by taking an azimuth to each. From the
known points plot the corresponding hack azimuths and they will
intersect at the point of observation. This process is called re-
•eetion. It is subject to errors of local attraction. (Par. 9.)
The accuracy of a location by intersection is affected by the rela-
tion of the azimuths and of the distances. The greatest accuracy
results when the azimuths differ by 90" or 270** and the distances are
equal ; in which case the two azimuths and the base form a right-
angled triangle. A difference of azimuths of less than 30 ** or more
than 330** should be avoided.
Brrors in length of the base, or distance between the known
points, affect the distances in the same proportion. If the base is 5
or lO per cent in error, both the distances will be in error in t^
same direction by the same percentage.
xHoarxxa raxs hahitai.
e most eBBllJ determined tram [ntenacttonB by plottlns
eratloD of Cbe unknown point maj be determined after the d
-. -, „ , .0 teotba and the laet tenth to-
htindredtbB.
Metallic tBpeii are ol IJnca with wires woven In lODgltudlnBll;.
Thej are eraduated In the same waj as tape chainB, and also la feet.
They stretch subtly.
right dlst
orefnllT whether
See that tbe Mn
hf end, and If the
the small dlvlsloii
i''%S"
le Bresped In both bsnds,
1 toward each other aloeg the rule, the tips
or pass, and by carefnily notlajf llieir relk-
e approximateli repn>duced at anf tlmi
ian5s, -'--'-- -'■- ■ ■- —
If a rule or rod (
down, with the oi
and tbe thumbs e
of the thorn ba mil
tlve positions a f._. __ _.,
by eraBpInK a atli^b In tbe bands, placing the thunibE In tbe proper
poaftion, and marhlng the outside of tbe hands. A length may be
measured In feet by pasxlng along IC hand over hand, placing first
tbe edges of tbK bands (ogptber and then the tburabs aa deacribed.
Every military tonographer ahould know the length of IiIb shoe,
his exact height, and tbe lengtb of his fore&nger. A copper cent is
It la Impra
■Fadostlno.
36, Table for «onveralon of lucheii and alxt
dirlmals i>t a foot and tbe reverse. The quantities In
thousandths of a toot. The decimal point la omitted.
JLMOiOrSMSSBMSCE,
Table XI.
37. X^HkB «f an lacfi In decimals of an Ivtilii
• t
A
tV
123
188
250
31S
375
438
t\
-»— — ■ —
1
625
— " 1 »
H
688
I
750
H
H
H
063
.500
563
813
— 1" ■
675
938
• 38. Ii«aii«tio» tofhe iiirrtacmtal'.^^Dlst&nces measured along
a slope may requJre'a borre'ction "before plotting th«fn on a map, as ali
map distances are, ov ar^ supposed to be, toeasut'ed In a horizontal
plane. Snch corrections, when made, ar^ called reduction to tbe
horlaontal. The following table gives Horizontal distances corre-
sponding to sloping' dIstaVices for gradients up to ^0°. This table is
to be nsed fa the same way as Tables II and III. The c<?rrectioh for
slopes of e** and less is too small to be ''plotted dn • the customary
scftlea and is UfeuaHy neglected. I& flat* ot <oi«lattfy rolling country
the correction wiH rarely bft necessaryi' i •.
Xable XII.
» }•
39. HorlsEohtal dlstatoceB foy irradjcnt^ of 0^ to 30* corr.espOi:\<|lr
ing^ to distances on thi? slope : \., r . ■ • ^
! »
. ... t
- » 1
■-■ '11 — ; A-'i — '-— i-i — -i 1 -' I ■ ' i i — «4** — •»'«* J *.
ffori^onW cligfances.for ^opin|: gUs^anceaof—
■ - - . ' ■ ■ ■' . . ' . .1 • ...'-.•
1^
X
i
; 2.
3
1 ,
1
i 4 ;
1
t
. 39994
. . 5 ,.
' ■ *» .
• . •••1.1
8-. ,
. -J.
1 »
.;.9 •
1
09998
19997
ao»9&
•49992'
. 59991
69989
' 79988
.89980
2
09994
19988
29982
39976
49969
59963
69967.
79961
89945
3
09986
19972
29959-
B9045
- 40931-
• -aSQlA
-«900ft
79600 i
89877
4
09076
19951
S9927
39902
i 49878
59854
69829
70805 \
89781
5
09062
19924
2»886
39848
408U)
50772
69783
7969&
89657
6
00045
19890
29886.
. 30781
49726
59671
• 60616
•» 79562'
• 80507
4
. 09025
19851
29776
39702
• 49627
59553
«9478
79404
'89329
8
09903
19805
29708
39611
49513
59416
69310
79221
89124
9
09677
19764
29631
39607
49384
59!$61
, «9138
79015
S8892
10
09848
19696
29544
39393
49240
59088
68036
78785
.88633
12
09781
19563
29344
30126
43907
58689
68470
78252
80033
14
09703
19406
29108
.38812.
48515
68218
. 67921
77624
87326
16
09fS13
19225
28838 t
,38450
48063
,57676
67288
, 76901
86M3
18
09510
19021
28532
. 38042
47553
67063
66674-
76084
85595
20
09307
18794
28191
. 37588
46985
5a3Sl
65778
75175
84572
22'
09272
18544
27815
37087
46359
55631
64903
74175
83446
24,
09135
18271
27406
36542
36252
45677
54813
^948
73084
82219
25|
09063
18126
27189
45315
54378
63441
72505
81568
26
08088
17976
26964
35952
44940
539^
62015
71903
80891
27
08010
17820
^488
35640
^ 44550
534S0
62370.
71280
80190
28
08829
17659
17492
35318
44147
52977
61806
70636
79465
29
08746
26238
34985
43731
52477
61223
69969
78716
30
06660
17320
25081
34641
43301
51961
60622
69282
77942
The horizontal distance corresponding to anv sloping dlstaocer and
a#»y angle or gradient may be found by multiplying the sloping dis-
tance by the cosine of the angle, Table XIV.
94346«— 17 ^3
84 . ENGINEB& VIELB HANUAI..
40. The protractor is an angular scale of equal parts used for
{>Iottlng azimuths. That adopted for reconnaissance Is the rectangu-
ar form (figs. 12 and 13). It Is graduated on one face, which will
be called the A face (fig. 12) from 0*" to 180 **» and on the other, or
B face (fig. 13) from ISC'* to 860". The graduation is clockwise on
both faces. It has a scale of inches and tenths along one edge. The
protractor may be used as ruler, scale, triangle, and parallel ruler.
To plot a arlven asliniitlft from a ari'ven polat, draw a
meridian through the point. If the azimuth is less than 180**, lay
the protractor down A face up with the center at the point and the
edge on the meridian, 0** to the north. Make a pencil dot on the
paper at the proper graduation on the edge of the protractor. Move
the protractor so that one of its edges passes through the two points
and draw a line, which will be the desired azimuth.
If the azimuth is more than 180**, lay the protractor down B face
up, 360** to the north, and proceed as before. The moving of the
protractor after setting off the angle and before drawing the line
may be avoided by adding a coanter-cloelc'wiae graduation to
the protractor. The sum of the two graduations at any point will
be 180**. Place the center of the protractor and the given azimuth,
read on the coanter-clockwi«e graduation, on a meridian, and
slide the protractor up or down, keeping the two points on the
meridian until one of the long edges passes through the given point,
when the azimuth mav be drawn along that edge.
A semicircular protractor is shown in figure 14. It is usually
double graduated, in opposite directions from 0** to 180**. With this
form an azimuth may be laid off and the line drawn along the diam-
eter without moving the protractor. Lay the protractor down with
the center on a meridian. If the azimuth is less than 180**, place
its number of degrees on the counter»cloekwl»e scale on the
meridian north of the center (fig. 15). If it is greater than 180**,
subtract its number of degrees from 360 and place the difference on
the clockwise scale over the north end of tne meridian (fig. 16).
In either case slide the protractor up or down, keeping the center
and the graduation on the meridian until the diameter passes
through the point, when the azimuth may be drawn along the
diameter of the protractor. Figure 17 shows a triangle graduated
for use as a protractor.
41. Improvtsed protractor*. — If a rule is at hand, a protrac-
tor may be made as described for slope board in paragraph 14 by
ext€nding the 1° graduations around a half or whole circle. If
wltlftoat compasaea, measure off the radius on a piece of paper,
stick a pin through one extremity for a center and a fine pencil point
through the other extremity and sweep the circle.
If wltliout a ralcy fold a piece of paper carefully through the
middle. The folded edge should be straight. Place the ends of the folded
edge toigether and fold again. The two edges now make an angle of
90^. Fold again through the middle and the angle will be 45"*.
Now fold in three parts and the angle is 15". Spread the paper out
flat and the creases will represent radii of 15" inte/vals. Tnese may
be divided into three equal parts by the eye, and the protractor will
then read to 5".
The hour graduations of a watch are 80" apart, and the minutes 6".
42. Tlie acale of a map is the ratio between dimensions on the
map and the corresponding dimensions on the ground. If the lengths
on map and ground were expressed in the same unit, the scale ratio
would always be expressed by the number of ground units corre-
sponding to the map unit. If 1 inch (map) corresponds to 120,000
inches (ground), the ratio, or scale, is plainly 1 — 120,000, or as
usually described, 1 to 120,000. This fraction is called the repre-
sentative fraction, and designated K. F. But ground distances
are so much greater than map distances that they are ordinarily ex-
-^ressed In a larger unit, which makes the scale ratio less apparent.
1 inch (map) equals 10,000 feet (ground), the scale is still 1 to
EBCOVVAXSBAHCX.
86
>?>v>>
a 60 cbTOnwAOoiioiioiao
100 TO THE FOOT.
ID to
SO
iiiiliiiiliiiilinil"iilii.ilniiliii-H sri
io
A
0
00
10 TO THE INCH.
U.S.
iimim
f T f Y V^^
Figr- 12. A Faoe
i5SSSSSSS5Sj5$SSJS^^
^
1^
m 99mmMomi»m9nm m
^
iinlniiliHilFinliinlmilmiliiiiliiiiliinH %
Flff. 18« B Face
0
00
iTiMiliinTiiiilmihiiiliiiiTT
Fur.14
s s
Ftir. 17.
Sid ENa»sx& vaasD icanital.
120,000, because 10,000 feet equal 120,000 inches. The map unit
Is almost al\Tays Indies, tience a good Tule for obtaining the
scale ratio is to reduce the given number of ground units to inches,
which will indicate the ratio.
Another method of stating scales, much employed in military map
makings is to take ratios which will give h* U ^* 3» 6, 12, or 15 Inches
on the map to 1 mile on the ground, and call the scales i, 1, 2, 3, 6.
12, or 15 inches to the mile. Sueh s^les can be put into terms
which express the ratio by dividing 63.360, the number of inches in
1 mile, by the number of Inches given in the scale. Thus, 1 inch to
1 mile equals 1 h- 63,360 ; 2 inches to 1 mile equals 1 -r 81,680 ; 3
inches to 1 mile equals 1 -i- 21420, etc.
The scale ratio is true for all viiita. If a scale ratio is
l-^9,600. 1 inch (map)=»9,600' inches (ground) ; 1 foot (map) =
9,600 feet (ground) ; 1 meter (map) =9,600 meters (ground), etc.
When the scale of a map is changed, as by reduction or enlarge-
ment, the B. P. changes too, and hence tne ratio should not be given
on maps which are to be reproduce.d. A linear scale ahoald be
draipvoL on every^ map. This will be enlarged or reduced with
the map and will always be true. Such a scale is ^Iso very conven-
ient for taking distances from the map. It consists of a straight-
line divided into equal parts which are numbered with reference to
the relation between distances on the ground and distances on the
map. The numbers relate to distances on the ground and the grad-
uations, or lengths set off on the line, relate to distances on the map.
A distance on the map equal to that from the zero of the scale to any
graduation corresponds to the tllstance on the gronnd represented
bv the number of that graduation. Steales are designated by" the' unit
of their parts, as scales of* lOilffsv .mettles of f eety scales of
meters, etc.
A scale might be constructed bv drawin&r a scale of inches on the
map and placing opposite the divisions the numbers expressing the
equivalent ground distances. It Is customary, however, because more
convenient, to take the numbers at intervals of JO, 100, or 1,000, or
multiples of them, and make the divisions of the line correspond. A
scale should be divided into a convenient number of equal parts
called primary divisions. The zerd Should be between the first
and second primary divisions, counting from the left. The primary
divisions are numbered from the zero to the right. The primary
division on the left of the zero is subdivided into smaller parts,
called secondary divisions, and these are numbered from the
zero to the left The secondary are usually J or j^y of the primary
divisions. . - -
To take off any distance from such a scale, put one leg of the
dividers on the primary division next below the distance sought, and
the other leg on the secondary division corresponding to the remain-
ing figures.
Figures 18 and 19 give scales for the usual range of topographic
maps, which may be taken off on the edge of a strip of paper and
transferred to a map. Figure 20 gives scales for plotting distances
measured by pacing on foot, and figure 21 for those by pacing
mounted. '
Scales may be constructed on strips of paper, wood, celluloid, or
metal instead of on the map, and are then called plotttngr scales.
The scales given in figures 18-21 are plottiflg scales. A distance
may be taken between dividers from any map and read by applying
the dividers to the proper one of these scales.
These scales are not engraved and can not be relied upon within
1 per cent. They are sufficiently exact for reconnaissance and, lu
fact, for most topographical drawing and scaling.
43. A series of points connected by azimuths and distances l^
called a traverse^ and the operation of determining the asimuths
and distances is called traversinar* The latter term' is usually
EECOHKAISSAKOS. ST
Fig. 18
R. F.—'i^=8!33 to f**633''6 to 1 mile.
10 987054321 0 10 f©et*
R. F. — T5o^ — "to' to f— 528'! to 1 mile.
10 9876648210 10 feet.
R. F. = sSo^'^V.^^ to \'=-U6J to 1 mile.
60 25 0 50 feet.
I I
R. F.= 600"""^^' ^^ l"= 105^6 to 1 mile.
/I
60 ^ 0 50 feet>.
[ ==1
R.F.= 4^-352' to r— 15" to 1 mile.
lOO 50 0 100 200 yds.
I »-l 1-4 1-4 l-l t-l i— I 1
R. F. — 5^=440' to f — 12" to 1 mile.
MO CO 0 100 200 yds.
R. F.= ^0^=833.3 to f'=6r34 to 1 mile-
100 0 100 200 800 400 600 yd».
R- F.— 10560 ="880' to r = 6" to 1 mile.
100 0 100 200 800 400 600ydfl.
R. Ff-^«1666:7 to r--3l'l7 to 1 mile.
IfiO 0
aoo
I — 1 1
R. F—jjIjo ~ ^7^° *® ^^ ^-^^ ^® ^ '""®-
100 0
T==r
1000 yds.
3
R. Fir- 52500 ""'*^^^*^ ^^ ^-2 ^*^ ^ '""'®-
logo 0
i-i i_i 1-1 n n ^-
1000
■ — I
9000 yds.
R. Ft- ^^zTT — 5280' to r— 1:'00 to 1 mile.
63360
1000 0
H H H H l-DE
1000
9000 yd&
R. Ff-i2g720^10560' to 1—0:50 to 1 mile.
1000 0 1000 aOOO 8000 4000 5000 yds.
HUWHtll. t I 1 IT
R. F.»'^.Lno=52800' to f=10 miles to I"
633600
10 9876548 2 10
10 miles.
3
( R. Ff-Y§g^-132000' to 1=25 miles to iT
10 0
10
3Z
20
30
40 miles.
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RECOSITAISSANaB. 41
extended to indtide all azimuths, distances, and elevations taken
while running such a line.
A traverse line with elevations along it may also be called a profile,
and when the traverse is run for the exprrees frarpose of taking the
elewitions, the operation is called proflllns^ and the line on the
ground and the plot of tt on paper are called proflles.
Distances in topography are so much greater than elevations that
both can not eonvenlently be represented on the same scale. It ^s
usual to take a scale for elevations called the -vertical scale, mvch
larger than the scale of distances, or horlsoiital aeale^ The ratio
of the two* scales is called the distortion or exassreration.
Ten or twenty fet»t to the Inch is a common scale for elevations. If
the horizontal scale ts 3 inches to the mile, the resulting distortions are
176 and 88 times. Both scales should always be written below every
profile.
Angles on a distorted profile are also distorted, and gradients can
not be plotted or read with an ordinary protractor.
Angles can be plotted or read on a profile by any . of the otb^r
methods of expressing gradients, paragraph 11 and Table I. The
horizontal distance is plotted to the horizontal scale and the corre-
sponding vertical distance to the vertical scale. A special protractor
may be made for any given distortion and nsed to plot and read
angles directly on a profile having that distortion. To make such a
protractor, lay oft a distance of 100 to the hbrtzontal' scale. At one
end of it erect a perpendicular and lay ott' on this, from the inter-
section, distances corresponding to 1**, 2", 3*, etc.; Tl%ble I, column H,
The.se distances must be laid off to the vertical scale, praw lines
through the points on the perpendicular anfl the other end of the
horizontal line. TJiese. lines represent the angles oil the profile
corresponding to the slopes on tbe fi^roiind.
44. Fleld-W'ork.— ^Measurements and additional notes may be ' re-
corded and afterwards plotted on a map or nla^ be plotted on a
map as taken or the two operations may be c6ifil)lned, as circum-
stances demand. A written report also will often be required.
45. A road sl^etch'coiislsts of a map gf the toad with ^ narrow
belt of oountry on either side. ' If roads, parallel and intersecting,
are not too far apart, the road sketches may bo Combined into a
fairly good map of tlje entire area.
The road Itself will, if practicable, be traversed with the degree
of precision already indicated as required for topographical recon-
naissance. If the couptry is open, so that long" 8igh|5 are possible, a
trained observer wjH ,gct better work by*. the use of the prismatic
compass and clinometpr. For shorter courses, when the object Is
of sufficient importance to use a chain for distances, the prismatic
compass and clinometer should also be used and the readings taken
with the greatest care.
Usually, however, the box compass will be used for azimuths and
the slope board for gradients, or else the sketching board, to be de-
scribed later, paragraph 55.
Side features will, if important, be located by intersection ;
otherwise by estimation. A convenient method Is to estimate the
distance of an object when it boars at right angles to the course and
plot it from that point. In such case the azimuth will be denoted
by B or L. Thus housb SOO R would mean a house at a distance of 300
units to the right on a lin^ at right angles to the course through
the point where the observation was taken.
4o. Traverslngr 'with compass and notebook, — Rule a col-
umn three-fourths of an inch wide down the center of each left-hand
page of the notebook. Select for the starting point some object or
point which can be identified by description. Standing at this point
Bight with the compass toward some object — tree, stump, telegraph pole,
or stone — that will serve as the second station of tne traverse line.
Note the reading of the compass and record It in the center column
42 ENCOHESE FXSU) XAEITAX.
ojf the notebook at the bottom of the first left-hand page, maklne also
the symbol for O 1. Observe and record also the azimuths of any
other objects which are to be located from 0 1. All the obserratlons
taken at this station are wrltt^i in order in the central colomn from
the bottom upward and are bracketed together with the station
symbol. The name of each object is written on the same horiaontal
line with its azimuth — on the right side of the page if on the right
of the traverse and on the left side of the page if on the left of the
traverse. If elevations are to be obtained, observe the gradients
from O 1 to the several objects and place each in the notebook next
to the corresponding azimuth.
Proceed toward O 2, counting paces. Halt when necessary to sketch
and measure offsets to objects on either side of the course, to take
bearings of intersecting roads, paths, streams, etc. When a halt is
made a mark is scored on the ground, the distance in paces from the
last O recorded in the central column, and the desired notes made.
Distances along the main line, azimuths, and gradient angles only
are re^rded in the central column. All descriptive matter relative to
side objects is placed outside of that column on the side corresponding
to that where the objects lie. Return to the scored mark and resume
the pacing, beginning with the number recorded at the halt, so that
the total count of paces at any point shall be the number taken since
leaving the last 0.
The center colunm of the page is taken to represent the line actually
paced and to be without width, so that offsets in the side sketches are
shown measured from the sides of the column and not from its center.
On reaching the second 0, record its distance from 0 1, draw a
horizontal line across the page, write 0 2 in the center column above
the line, and continue as before to 0 3.
It is well at 0 2 to take a back azimuth on 0 1. This should difPer
from the azimuth of 0 2 from 0 1 by exactly ISO**. A marked discrep-
ancy indicates error in observation or the effect of local attraction on
the needle, and should be investigated before proceeding. If a back
azimuth is taken it should be the first observation made and recorded.
When opportunity offers, take bearings on distant bends of the road,
spires, towers, hilltops, tail trees, etc., and enter the angles in the
center column with the name of each object written beside its bearings.
Endeavor to get bearings of the same distant object from several sta-
tions or from two stations at some distance apart. These, when
plotted, should intersect at a common point If the observed bearings
are correct and the compass bas not suffered local disturbance. It is
not to be expected In work of this grade that an exact intersection of
more than two bearings can be obtained except by accident.
When a sketcher at any point of the traverse finds himself in pro-
longation of a line that defines or bounds a feature of the country,
such as a fence, the edge of a wood, a reach of shore line of river or
lake, a gully, canyon, or ridge, a face of a building, or a stretch of
road or railroad, its bearing should be taken. The same rule should be
observed when Important features come into range with each other
from a point on the traverse. A valuable check on the relatly^ positions
of such features Is thus obtained.
If a traverse line is interrupted by any obstacle that interferes with
the measurement of distance, its width should be estimated and the
pacing resumed on the other side ; or, for greater exactness, make an
offset, perpendicular to the traverse line ft possible, long enough to
clear the obstacle, continue the traverse parallel to the original course,
and return to the latter after passing the obstacle by a second offset
naraUel and equal to the first and in the opposite direction ; or, locate
•'ints on the farther side by intersections.
17. The unit of measure should be cl«axlr stated in tlie
item. Ordinarily distances along the course are In paces, while
ima^ted offsets may be in paces, feet, yards, or fractions of a mile,
) their distances, and also according to the unit in which
r finds he can make the closest estimate.
BXcaniAisaAifCB. 4S
On the usual reconnaissance scales the dimensions of buildings,
width of roads, bridges, etc., can not be plotted to scale. They are
shown exaggerated^ and the true dimensions, if important, must be
given in figures.
4& Tbe best metliod of plottlngr is to plot the traverse lines
and the check bearings first. Then any error discovered by means of
the latter, or by closure on the initial or other known point can be
more readily corrected. When the traverse line has been adjusted,
the details on either side are plotted in and do not bave to be changed.
TMe outfit desirable for the method of traversing with compass
and notebook is the following: Notebook or sheets of paper ruled as
described, prismatic or pocket compass, pencil of medium hardness,
rubber eraser, pocket knife, 25-foot tape, a piece of twine 100 feet
long. The absolute necessities are the paper, the compass, pocket
knife or pencil sharpener, and rubber-tipped pencil. The tape measure
is to be used for making small measurements of distance or dimen-
sions. The cord is useful for measuring depths of water, heights of
structures, etc. It should be graduated to yards by knots.
49. Tlae topoflrrApltlc field notebook is designed to facilitate
the foregoing method of traversing. In addition to the central column,
it has columns on either side in which to record the offset distances,
each of which is put down on the proper side of the central column,
avoiding the necessity of using the letters B and L, and eliminating
the liability of mistakes in confusion of the direction.
The opposite right-hand page is ruled In 1-inch squares, and has a
full-circle protractor graduated to degrees printed on it. This page
facilitates a hasty plot of the traverse with respect to which many de-
tails can be sketched in more clearly and certainly than they could be
recorded in writing. At the bottom of the page are scales of tenths
and eighths of incnes. The alternate pairs of pages are plain ruled
for notes and memoranda. Figures 22 and 23 show the arrangement
and illustrate the use of the book described.
60. TrAirerslBir wltM compass and drawlnar board. — ^The
observations are taken as in traversing with a notebook and compass,
but the traverse line and such offsets as come within the limits of the
sketch are plotted at once ; that is, the map is drawn as the observer
proceeds over the ground. A great advantage of this method is that
any large error in measurement is likely to be detected by the eye, as
the map is compared with the ground, and errors can be corrected on
the spot. The plotting scale of equal parts should be prepared before-
hand to suit the scale of the map. If this scale can be pasted or
drawn on the edge of the protractor opposite the angular graduation,
it is a convenience.
The sides of the sheet of paper should be letered N, E, S, and W to
correspond with the points of the compass. If the paper is ruled or
water-lined, the lines are taken parallel to the magnetic meridian.
Having observed the azimuth at Q 1, draw through the point desig-
natinsT that station a line having the observed azimuth. Azimuth
lines are erased finally as a rule, and hence should be lightly drawn
and with a fairly hard pencil. Prolong this line in the direction of
O 2 far enough to surely reach that 0. If other azimuths are taken
at 0 1, plot tnem also, and note on each the object to which it bears.
If the distance to the object is estimated, it may be laid off on the
azimnth and the position of the object plotted at once.
Proceeding toward 0 2 to take any desired side shot, halt abreast
of the object, plot the distance from 0 1 on the course, estimate the
distance to the object, and plot It in at that distance opposite the
point plotted on tne course and on the proper side.
Arrived at 0 2, lay off the entire distance from 0 1, and plot and
mark 0 2. Erase the azimuth line beyond 0 2; take and plot any
other desired azimuths. If any of them are to points previously
sighted to, make the intersections and plot and mark the points. In
plotting azimuths to side objects, it is better to draw only a short
part of the line near the object to avoid confusion of lines on th<^
sketch and especially near the station.
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ESCONNAXSSAKeXi
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46 ENGINSE& FIELD ICANUAL.
51. Tlae follo^lngr outfit Is desirable for travertsing by this
method : A thin, smooth board 12 by 15 inches, to which the paper is
attached by thumbtacks or rubber bands, prismatic or pocket com-
pass, clinometer or slope board, a rectangular protractor, a plotting
scale, lead pencil, No. 3 or 4, rubber eraser, 25-foot tape, 100 feet
of ttvine, watch, pocket knife, canvas cover for board and paper, note-
book. A field glass is also very useful. Good work can be done with
a less elaborate outfit, or with improvised arrangements for some of
those mentioned. The drawing board may be utilized as a slope board.
52. A road sketch will be long and narrow, and two or more
stretches should be got on a board if possible, in this way a board
of the size indicated will hold a fair day's work. When a section
runs off the paper mark it with a letter, as A, and make a note, Coii-
tiniied at B. Mark the beginning of the next section B and write
Continued from A.
Wherever else a road runs off the map, make a marginal note
" To , miles," giving the name and distance of nearest
settlement or conspicuous topographical feature. If the road crosses
one parallel to the main route, write also " To crossing,
miles.*'
53. Traverslngr 'with oriented dra^rlnir board. — A drawing
is said to be oriented when so placed that its true meridian is parallel
to the true meridian on the ground. When using magnetic azimuths,
making the magnetic meridians — ^inap and ground — ^parallel, may be
accepted as a proper orientation. Wnen a map is oriented, with any
given point vertically over the corresponding point on the ground, a
ruler held on the point or station on the map, and pointed in the
direction of any object gives the azimuth of that object on the map.
No angular measurements need be made. A compass is not neces-
sary, but It is very convenient as it affords the quickest means of
orienting the map.
54. To run a traverse by this method assume on the map
the initial point and the magnetic meridian, selecting them so that
the general direction of the traverse will coincide with the longest
dimension of the paper. Place the board over the first station ; lay
the compass on it with the north-and-south line parallel to the
assumed meridian, and turn the board until the needle reads north.
The board is then oriented, and must be in this position whenever
a sight is taken. It should also be level, as nearly as can be deter-
mined by the eye.
Place a ruler on the station point of the map and sight It in the
direction of any object which it is desired to plot. Draw a line
along the edge of the ruler and on It lay off to the adopted scale the
distance of the object if known or assumed. When all the desired
azimuths have been taken from the station, sight the ruler to the
second station and draw its azimuth, and then proceed to that
station, pacing the distance. Arrived at the forward station, plot
the paced distance, orient the board over the station, and proceed as
before. If any of the objects taken at the first station can be seen
from the second, new azimuths mav be taken to them which will
locate them by intersection (fig. .24). If no compass Is at hand,
orient the board arbitrarily at the first station, and at the second
station orient it by placing the ruler on the line between the two,
and sighting back to the station Just left. EMgure 25 shows the
relative positions of board and ground at four successive stations.
55. Traverslnsr with sketching board. — The sketching board
(small planetable) is a compact device for traversing by the oriented-
map method. The compass is set into the board, and a movable
index is provided which can be revolved to place it parallel to the
assumed meridian on the map. When the needle is* brought parallel
to the. wire the board is oriented. The needle may be parallel to the
index wires, but end for end, or ISO** out of its true position, in
n^hich case the sketcher la turned completely around, such a mls-
ke is so great and so obvious that it needs no preventive, but a
tcher may note at the outset whether the N or 8 end of the
&BcoinrAZS8Jkjrcx.
47
Position at 04
Traversing by plane table and ResectioD
iB ENGXKXUk VntJ} KANTTaL.
needle id toward the stud~wbich moves the wttes and keep it in this
position.
56. The Engineer Department has designed a standard reconnais-
sunce equipment (flgs. 26 and 27 )\ based solely upon the plane-table
method. All forms of sketching board, with ruler attached to the
board, have been discarded. The design and plan of assigning the
eciuipment to the several arms of the service has been approved by
the Secretary of War. The outfit is divided into equipment, which is
Sormanent, and' supplies, which are expendable. The complete out-
t is:
EQUIPMENT.
1 alidade^ 1 holder, timing pad.
1 board, sketching. 1 pace tally.
1 chest, sketching outfit. 1 pencil pocket.
1 clinometer, service, with case. 1 tripod, wood, folding.
SUPPLIES.
12 celluloid, sheets. 6 pencils, drawing, H.
2 erasers, rubber. 2 pencils, green.
6 pads, timing. 2 pencils, red.
72 paper, sketching board, sheets. 2 protectors, pencil point.
2 pencils, blue. . 2 tape, adhesive, rolls.
The approved distribution is one outfit, as listed above, to each
regimental and battalion headquarters of infantry, cavalry, and fleld
artillery, and three to each engineer totjl Wagon, giving six per com-
pany or three per mounted company. Headquarters of higher engi-
neer units and division or chief engineers not attached to engineer
units receive normally three such outfits, but division and chief en-
gineers may receive a larger number if they so requisition.
The alidade is a triangular scale, -10^ inches long, weighted at the
ends, is conveniently graduated and has blank spaces for pasting on
individual scales of paces, walk, trot, and gallop.
The board is of g-inch white pine, with end pieces to present
warping, and has screws over slotted washers in the ends to permit
of expansion. The needle is 3 inches long and quite sensitive. At
each corner of the board is a substantial clip to hold the paper firmly
in place. No plumb bob is provided, but a hole t» accurately bored
so that a plumb bob can be improvised and use made of the slope
scale on the board in case the clinometer should be lost. The plate
on the back of the board is let in flush so that the board can b»*
turned freely on the tripod for orientation and then firmly clampe<l
by a slight turn of the tripod screw. As the tripod is not used in
mounted sketching, holes have been bored at the corners of the board
for the insertion of a carrying cord if desired.
The tripod is of wood with telescoping legs, which fold to 15 incheR
or extend to about 40 inches and detach from the top for packing in
the container. The top, also of wood, is provided with a heavy-
thumbscrew for attaching the board, and is covered with felt to grive
a Arm bearing without sticking or binding.
The celluloid sheets are for use Instead of sketching paper during
rainy weather.
KECOSHAUSAIICZ.
EHQINEER FIELD MANUAI..
BEGONNAISSAJrCE. 61
57. A road reconnalsaance should procure datn on the
follofvinar subjects t
The road. — Gradients, especially the steepest ; width of roadway ;
if paved, width, kind, and condition of paving; width and depth of
side ditches, and whether wet or dry ; if not paved, character of
soil; sand, day, or gravel ; kind of fences and width between them.
The sketch should also show where the road is In embankment or
cutting ; where wagons can not double or pass, and where foot troops
can not march along the side between the wagon track and the
fences
Bridges. — ^Material of piers and abutments ; type and material of
superstructure, as girder, truss, arch, suspension, wood, steel, stone,
etc. ; width of roadway, and clear headroom ; safe load (see Bridges).
Of bridges over the road, clear width and height; over streams, the
nearest bridges above and below and whatever information can be
obtained about them.
The country. — Character of cultivation or natural vegetation ;
areas and densi^ of timber, underbrush, vines, especially poisonous
ones ; marshes and fords, Mnds of fences, nature of soil ; general
configuration of surface, especially high hills, long ridges or valleys,
bluffs or slopes too steep to scale, . and practicable routes to their
crests.
Streams crossed.^ — ^Name, width, depth, and surface velocity in
swiftest current; velocity noted as sluggish, moderate, quick, or
swift ; elevation of high-water marks in relation to the road ; which
bank is the higher at crossing and above and below, and how much;
accessibility of water for stock ; fords at or near crossing ; length,
depth, and steepness of approaches; levees or embankments, height,
and thickness on top ; if navigable, to what distance above and below
and for what class of vessels — steamers, flatboats, rowboats.
Towns and vUlasres passed through. — Name, location on map,
and population. Names of streets to be traversed. Material, as
stone, brick, frame, log; size, 1, 2, 3 stories, and distribution, close
or scattered, of the houses in those streets; gradients of Intersecting
streets ; location of railway depots, post, telegraph, and telephone
offices ; of drinking fountains and watering troughs ; of elevators,
storehouses, or other accumulations of food or forage ; of blacksmith,
wagon, and machine shops.
I^hen ordered to malce a complete examination of a
town ' or village note besides the foregoing, location and size of
Jtrlnclpal buildings, halls, court and school houses, churches, banks,
ails, and their ownership ; sources, maximum quantity and distribu-
tion of water supply ; sanitary conditions ana disposal of wastes ;
location of railroads, depots, freight houses, sidings, etc. ; for all
roads entering from the surrounding country the same information
as scheduled above for streets; location and extent of open spaces.
and of large substantial buildings standing apart ; location and extent
of blgb ground within range, especially that from which streets can
be enfiladed. ^, . , ^ .. ^ . .,.
Railroads crossed. — ^Name, gauge, single or double track, sidings
and loading platforms at point of crossing; crossing at grade, over
or under; distance and name of nearest station each way; direction
and distance of nearest roundhouse, shops, etc.
58. River reconnaissance. — Designate the banks as right or
left, the right bank being that on the right hand when looking
down the stream. If, when standing on the bank facing across the
stream, the current flows from left to right, the observer is on the
rifflit bank ; if from right to left, he is on the left bank.
if the stream is navigated, pilots and residents will know distances
by channel between landings with sufficient accuracy for the purposes
of a field reconnaissance. In making a traverse along the banks of
the liTer, it may be desirable to cross from one side to the other to
i^ AJ^IUHIIBI^ ^OBCI
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r^fA/.^, ^M*.' . *{/1j^ f/r ('•i»^^«;^y, tf.-^^A «V>-iM n/it be motv ttian 4 feet
F^'N^f/f f^<i» f-ttymSti, %^ 1f-H U^ lf.f»Mrj, stnA 2 (tftt 4 inches for
iff ft- if./f t^t^tfo ihifUi-tf ^.r* n^t\,f^ «A »pc.r/»rfw!!f to bridees and
r//Mf^. ii\f\\h M fffnn^nv. nUtpn^, «//», HTe^rt of w^mtlicr and tTaAc.
M'^/a A-/fA'f*f|^ fM /J#r#riae)Nfnf/ tit fffi^g^ and fords.
I^fifhthm, httniHt mm4 *fth^r m^Mm» ot ermmmlmm' — Position of
Ifniki ■fiiifthhfUfn $ufi jffnrnfnMUif fftr horses and loaded wagons:
'»'^^-' fmthif't. nttfi ti)inU of ^tffnfM: method of propalslon ; ^Ites for
hfUjhnj hti(fi(rn Of ft*ttif''^' /'tmrHHef of site for constmetion, uso,
Mofi ntfhfttthj iftn9Uo)if of U^nu^n And trJbutary streams; approaches
Hui] r^hifth or loutkA , ¥fUUU of rlvcf snd fnaximiim surface Telocity of
hut [hill- u *ih*ntni tor Vtti I'ottntrwilon or repair of boats, bridges,
fiH«i«flHlli<ffS' t*^ni't^H ttuUiiUn for Inundations by dsmmlng or ob-
»Ii(mIM)« m U'tnow hi\tUti niino, or by cutting a leree or dike. Noto
{|ilM>.i| jh.tiJK MM uMMiMjl )lntil(i Id tmlursl or artlflclal inundations and
M)M HMf»..«l |mmU III f»il|M«r liy known landmarks when the road Is
HujiiMtMil Sit iiMi^ittih^ litutidMllon 2 fi'M deep on level ground is
ri Hi-HnMrt HltqjiU'li* Mdluttn fhu I'oiulN t\Tfi* vfry sound and marked by
hh»''' l'H«|.i I'll liuni v^ht1u mo mitrkiMl a dip In the roadbed of 3
M( \ I >M( iHMv iMKiltM- ni»i iHmd tntimHHAble, A railroad bed is soon
'Mt |ii>|(M«Mu«UaiiMMM« ur M riiMrofid. -The lln^. Local name ;
MMulMM huhtU iMul «tUlHiu*«ti4 lH*tvvt'*»n stiittouH and other points ;
ttM>«h»'. »\\\*.\\\ \\\; \\\\\\\\\k\ ti'hi'HJ nuutttlon of roadlKHl. ties, and rails:
(l*MH»iU,»« .M\\l M.kUnhv u\ itvtM'ttowM v»r wuiihouts: faculties for repair;
v*«H»lh«<*M \\\ \U.U\ \,k\ \\,\\ t\iV \\\m\A\\\\& ti\Htp« aUmff the line.
» iM\M» l?i w»u| liv(«iii%»«iv NumlH^r ami location: dimensions;
hUs \\< \^\\\\\y^[ i\WA\\^ vvC iW«t(\»>lu)£ Miut rt^v^ilrlnjp: of blocklni^
iMwyi *1*^^K. Nv»mt^v a>ut nature of w»s:ln^>« and cars arall-
, ^p>U\ uM l^*»»*is»»u»»»i ti\sMw tvtw^w iiWu p<4bIs: facilities
vwUsusiu, ^^mouM utUu>», ^^x x^vAiv r5<iK old binlWia.. etc; locm-
BEOOKHAlSSAirCB. Ik
Stattoiui. — Name and location; facilities for entrainlnisr and de-
training troops witli wagons and horses; platforms on throngh Itne
and sidings ; ramps ; sldetraclcs, number and capacity ; turntables ;
water tanks; fuel supply ; storage facilities; derricks or cranes;
cross-overs for teams and pedestrians. Facilities at liand for hos-
Sitals, camps, depots ; for feeding men, heating cofifee, watering horses
uring temporary belts.
Otlier communications. — Telegraph lines ; number and location
of stations, number of wires ; connections ; parallel highways, roads,
riyers, or canals ; means of access from same to railroad ; junctions
and crossings of other lines ; relative elevation ; facilities for laying
temporary switches and sidings at stations or between crossing lines.
Defenstbilttr* — Heights commanding line of road ; defense of
stations ; defense of road and telegraph lines against raiding parties ;
structures exposed to demolition ; defense and attack of same ; defiles
and river crossings.
60. ReconnalsMince of a ^wood or forest. — Note all roads
and paths, and all hills, . ravines, and streams within the wood or
skirting the edges ; kinds of trees, density and growth ; underbrush,
prevalence of poisonous shrubs and vines ; marshy or large open
spaces ; practicability of forming new roads by cutting ; creation of
obstacles by felling trees ; if there are no roads traverse the shortest
practicable path between the point of entrance and point of exit, and
mark bowlders or blaze trees, set stakes, or otherwise Indicate this
path, and also give compass bearings of the route to be followed.
Note the exterior forms of the woods, whether parts of the edge
flank other parts ; connection with neighboring pieces of wood by
scattered trees or clearings ; undulations of the ground that would
give cover to attacking force or to defenders.
61. Reconnatssanee of monntains. — Note the number and
{>o8ltlons of paspiei through the mountains, of roads and trails lead-
ng to these passes. th«r condition, practicability, and means of
rf'palr; steepness of slopes on the sides of roads: means of con-
structing additional roads ; watercourses, their direction, nature, and
time of floods ; means of crossing. Note ravines and open glades on
mountain sides, lookout points, and good signal atations ; note time
and duration of snowdrifts on roads or passes ; depth of drifts and
possibility of removing them or of traveling on the surface of the
snow. Note extent and nature of forest growth.
62. Reconnaissance for a camp or ^winter quarters' —
Site. — Location, elevation, and area; sanitary features, such as
draina|;e» dryness, and general character of top soil ; proximity of
swampy ground or stagnant ponds.
Commnnications. — Sufficiency of existing roads and paths,
maximum grades, probable condition under heavy traffic and In bad
weather, location and kind of materials available for Improvement
or repair, railroad or water communication and terminal facilities
of same.
'Water and fnel. — Location, kind, and quantity of fuel at hand ;
quality and quantity of water ; facilities for filling water carts, for
watering animals and for washing and bathing: nature of supply, as
wells, springs, running streams, and Its reliability.
Slielter and conveniences. — Proximity of trees, brush, wood,
hay, and straw for huts and bedding ; of markets ; of towns and
Till Acres.
Def e'nsibility-. — Location of outposts and guards ; location and
character of defensive positions In or near the camp ; force required
to hold positions which may command the camp.
63. Reconnaissance of a position. — This problem usually in-
cludes the selection of the position, and is therefore tactical as well
as topographical. Certain relations and conditions must be observed
in the selection, and the extent and degree in which they are found
must be clearly shown on the map or in the report.
Tli« lenflTtn of the poslton, or itp development along the firln*
line, should be proportional to the force available for its occupat^
M ENGINES& FIELD KAKITAL.
SIxact rules can not be given, but 6,000 infantry per mile or 3 men
pel- yard is the usual ^estimate.
The flanks must be secure. Impassable natural features, a
river, mountain, or stream form the be^t flank: Lacking these, a
wood, a deep ravine, a cliff, or a high hill will serve. Even with
these features absent a flank may be. strengthened by the construc-
tion of a strong earthwork, but the general rule obtalins that natural
weakness of the flanks must be made up by a greater number of men,
or by the substitution of cavalry for Infantry in case the ground
favors the movements of mounted troops.
If the flamks are naturally strong: the line should be with-
drawn to make the entire position reentrant; if the llaAks are
naturally ^reak the connecting line should be held straight or
advanced so as to make the position straight or salient.
The Aeptli of the position, or its extent in. rear of the firing
line, should afford natural cover for supports, reserves, and trains,
which may require a total depth of 800 to 2,400 yards, but a short
position may be relatively shallower than a long one. Three or four
parallel ridges, 300 to 600 yards apart, with the intervening ground
practicable, form an excellent position. If the first ridge is somewhat
higher than the rest, so much the better. Whatever cover there may
be for the component parts of the force, whether natural or artificial,
fences, ditches, trees, etc^ should be shown or described. If digging
is necessary, its amount and the character of .the soil should be
stated.
StronflT points in front of the line, which may be occupied
as outposts, should be shown.
COnunpnieation should be free in every direction, concealed
80 far as possible from the enemy's view.
ArtUlery positions are required when that arm Is represented
In the occupying force, as will usuallv be the case. They should
permit the guns to sweep all ground in front of the position over
which the enemy can advance to the limit of effective range. Every
point in front of the position and within range which commands any
part of it is an element of weakness.
Ranges at which the enemy can be seen and reached by artillery
fire ; the points beyond rifie range covered by such fire and its
relative command of adverse artillery positions should be shown or
described.
If possible, similar information should be obtained of the ground
likely to be occupied by the enemy, in forming for attack or in
taking up a counter position.
64. A position occupied by an enemy must be reconnoitered
from a distance, and few details can actually be seen. Valuable in-
ferences may be drawn by remembering that the enemy has probably
chosen his position in accordance with the principles above given.
Especial attention should be given to the flanks and the feasibility
of turning one of them.
65. A position sketch will usually be on a scale of 6 inches or
12 inches to the mile. It will be found most convenient ' and ex-
? editions to make it by the compass and drawing-board method
par. 50) or the method with oriented board alone (par. 54). The
traverse will include the fewest points from which the entire area
can be seen, often only two, and all other features will be located
b^ intersections from these points. Elevations may be taken by
slope board or clinometer, the height of the first point occupied being
arbitrarily assumed if not known.
If two points can be found which overlook the area is front of
them and which are also visible from each other, the con&pass nuty
be dispensed ^with except for a meridian. Measure the distance
between the two points. Assume the position of one of the points
and 9t the line Joining them, so as to bi-ing the desired area on the
paper. From the first point lay off on the line the distance between
the two points to the adopted scale and plot the second point. The
n
BSCONNAXSSANC& W
line joining tbe two Is called the 1>ase, and will be near one edge
of the board if all the area to be mapped is on one side of the line
or toward the middle if it is on both sides.
Place the board over the first point; lay the ruler along the base
and turn the board until the ruler points to the second point. Keep
the board in this position and point the ruler successiyely to the
objects to be located, drawing the lines as explained in paragraph 64.
Gradients are written along the corresponding azimuths. One
gradient should be taken to each point determined.
Proceed to the second point. Lay the ruler along the base and
{>oint It to the first point. Point the ruler to the objects to be
ocated, marking where it crosses the line to the same object drawn
from the first point.
66. ContourinflT Is a method of exhibiting relief of ground by
means of lines so drawn on a map as to indicate points of equal
elevation. The lines so drawn on a map and the corresponding lines
on the ground are called contours. The word contouring is applied
to the fieldwork directed especially to obtaining data for drawing
contours.
The ditference of elevation of points in adjacent contours is called
the contour Interval, and Is usually constant for all the 'contours
on the same map. The horizontal distance between contours, meas-
ured In a radial direction with reference to the curvature of the
contours will be referred to as contour distance.
The theory of contouring is that no inadmissible error will be
made by supposing the slope of the ground from a point in one
contour to the corresponding point in tne next, or along the contour
distance, to be a straight line. The less tbe contour Interval, the
less error will be made. If in figure 28 the curved line AB represents
the actual surface of the ground, and points 1, 3, 5, the elevation
of successive contours, the broken line 1, 8, . 5, will represent the
assumed ground surface, and its departure from the line AB is the
error Introduced. If now the points 2, 4, and 6 are also determined,
or the contour intervals be reduced one-half, the assumed slope is 1,
2, 3, 4, 5, 6, which differs less from the line AB than the line 1, 3, 5,
and hence Introduces less error. With points determined at very
short Intervals the error is practically eliminated.
If contour distances decrease with elcT^atton,. or the contours
become closer as they go higher, the slope is conca^^e, and points
between contours are lower than the straight line joining correspond-
ing contour points. If the contours become closer as the ground falls,
the ground Is convex, or lies above the straight line joining cor-
responding contour points. A point of inflection, or change from
convex to concave, is at the point where the contour distance is less
or greater than those on either side of it. Bqnal contour distances
correspond to uniform slope.
67. One contour does not necessarily join all the points of the same
elevation on the map but only those which have a continuous series
of points of the same elevation joining them. It may require several
contours to take in all the points of a given elevation on the map.
Parts of the same contour will appear a^ separate when the ground
over which they could be connected Is not on the map. The selection
of tbe points to connect in one contour Is the difficult part of the
process and can not be done correctly without thorough knowledge
of the principles of the method and a good idea of the general shape
of the ground to be contoured. In military reconnaissance only
enotigli elevations can usually be taken in the field to guide one
who has seen and studied the ground in drawing the contours. No
one who has not seen and studied the ground should be expected or
permitted to draw contours from such data. Brroneous information
may be worse than none at all.
eS. For equal contour Intervals the map contours are closer to-
gether as the slope is steeper. It follows that for steep slopes the
map contours will approach each other very closely, and for a ver-
tical wall or cliff they will coincide.
FIELD TUSVAL.
I'l=4=
aaCOB J AT88 AWCg. 07
Ground contours can not cross, but map contours may cross In the
very unusual case of a cave or a bluff overhanging by an amount
which can be shown on the horizontal scale. Thiis is so rare that it
is usual to say that map contours can not cross.
Every contour must close upon itself in a loop or else must extend
unbroken from one point on the margin on the map to some other
point on the margin. An exception is made in the case of large
streams, the contour on each bank being carried upstream until it
cuts the water surface when it Is dropped. The two ends must be
directly opposite (fig. 29). In a small stream or dry bed» the contour
crosses at the point where the elevation of the bed is that of the
contour (fig. 30).
Maximuin ridge and mlnimiiin valley contours go in pairs. A
single lower contour can not He between two higher ones, or a single
higher between two lower. When two adjacent contours have the
same elcT-atlon, the ground between them will be still lo-wer if
they are valley, or still higrher if ridge contours.
69. Contours are designated by their heights above a datum plane.
The height is expressed in feet, except when the metric scale is used,
when contour intervals are in meters.
The elevation of each contour should be shown in figures at points
close enough together to allow the eye to run from one to the other
with ease. It is best to break the contours and write the numbers
between the ends.' If written alongside, the numbers should always
be on the higher side of the contour (figs. 31 and 32).
70. Straight contours are very rare. They may be determined by
locating any two points, or by locating one point and observing the
azimuth of the line.
Simple curved contours are more frequent than straight ones, but are
not often found of any considerable length. They mav be determined
by fixing 3 points ; or by 2 points with the radius estimated ; or by 1
point with the cehter assumed.
The typical centenr is a wavy line, alternately salient and
reentrant, and may be determined with the precision needful for hasty
reconnaissance by fixing the extreme points of the convex and concave
portions.
71. Looking at contours froM the higher side, the salient parts, or
those concave to the observer, correspond to the ridges, and the re-
entrant parts, or those convex to the observer, to the valleys. The
valleys are also lines of drainage. Hence, half of the points necessary
to determine a wavy contour will lie on drainage lines, as indicated by
rivers, creeks, brooks, and rivulets, and by ravines, or other depres-
sions dry at most seasons.
The slope of a drainage line grows less in the direction of flow.
Tributaries, or branches, are usually steeper than the main stream at
their Junction, and also increase in slope toward their sources. Gen-
erally, in a limited area, the sources will be at nearly the same ele-
▼ation. To apply this principle in increasing the amount of topo-
graphical relief that may legitimately be drawn from a given number
of known elevations, let figure 33 represent the drainage lines of an
area taken from a civil map. Suppose the ground to have been studied
and elevations to have been determined at 2 points, A and B, How
mucli topography can be drawn?
The 110-foot contour will be above the 105-foot and by a distance
somewhat less than the length AB, because the slope becomes steeper
and the contour distance less in going upstream. The succeeding con-
tours at 10-foot intervals will cross the tributary at gradually decreas-
ing distances, as Indicated, and for the same reason. The source is
found to be about 130 feet. Take the other sources to be also 130 feet
and draw the contour at that level, remembering that it is concave
where it crosses the streams, and that the part between the streams is
convex and advanced. Lay off the contour points on the other stream
lines, keeping in mind the law of slopes, and draw the other contours,
following the same rule as for the first.
tt
ENGZHEEK FIELD KAHVAL.
flflr.83
r $r 5^^ fa V M^ fiS 66 A Jo 49
Flflr.84
BBCOHNiJSBAHCS. »
72. If enongh eleyations were taken on stream lines the concave
parts of tbe contours would be fairly well determined, but the convex
points would still be in part uncertain. It is known that they are
convex and salient, but not how much. This information is supplied
by elevations taken alone the ridges, crests, or divides which lie be-
tween adjacent drainage lines. The typical profile of a crest is a re-
versed curve, flat and convex between tne sources of streams, flat and
concave near the junctions of streams, and steepest in the middle, with
the inflection at the steepest point. The form of crests is not so regu-
lar as that of vallevs, and less use can be made of it. It should oe
kept in mind as a basis of comparison, so that actual forms can be
more readily remembered.
73. Tke Held 'work of coatonriasr an area which has a suffi-
cient relief to exhibit drainage lines clearly may begin by traversing
these lines with gradients taken by clinometer or slope board. It u
most convenient to begin where collected drainage leaves the area to
be mapped and follow each valley to its source.
If the valley is open and the flanks of the ridges on each side can be
seen, time may be saved by taking level sights from some of the con-
tour points on the drainage line to points on the ridges ieis far ad-
vanced as possible, usually where the line of sight is tangent to the
hill. This gives two points, a a (flg. 33) near the apex of the salient
from which the contour may be drawn often as well as by a point at
the apex. If this can be generally done it may not be necessary to run
out the ridges. Notes should be made of the apparent sh^pe of the
contours near the drainage line, whether sharp or blunt, or whether
the vallev Is narrow or wide. The general shape of the sky line of the
ridge or its projection against higher ground should be noted whenever
a lateral view of it can be had.
If hill points can not be taken from the valley traverse the ridge
lines must be run out. They must be connected in plan (distance and
azimuth) and in elevation with the drainage lines. When drainage
and ridge lines are plotted on the map the contour points, if not actu-
ally observed, may be interpolated and the contours drawn.
The symmetry of adjacent contours is obvious from the Inspection
of any contoured map, and this relation may be utilized where one
contour bas been well determined, to draw the one on either side of it
from a very few points, often but one. If the contours are wavy they
will generally be a little farther apart at the conca^ie and convex
points than at the reversion points between them. If the contours are
not wavv they are generally parallel.
74. If the relief of the ground Is so sllffht that the drainage
and ridge lines are uncertain the field work of contouring is best
done by taking elevations at points arbitrarily selectc^d. Such points
will usually be in straight lines running in the general direction
of the steepest slope. The points are plotted on the map, the cor-
responding elevations written near them, and the contours are
Interpolated as indicated In figure 34. assuming that the surface of
the ground between observed points is a straight line. The closer
the points are together the less error is Involved in this assumption.
If the country is comparatively flat and unbroken, profiles may
be run along roads and paths and contours sketched in on each
side so far as they can be seen. Then by going over the intervening
ground and observing its shape, the portions drawn can be Joined with
the eye with sufficient accuracy.
In towns and villages profiles along intersecting streets and the
study of the intervening space furnish data for approximate con-
tours
75. Slope e^niTaienta. — ^^A.ctual distances between contours on a
map depend on the contour interval, the scale of the map, and the
gradient. For any given map the contour interval and scale are
constant, and the distances between contours depend on the slope
alone. On any map with contours at equal interrals each gradient
has its corresponding contour distance, which is called Its eaaiva-
es EHanrsER fislb kahval.
mounted can cover 15 miles a day steadily, or in an emergency 20
or 25, and can keep np with Infantry on a forced march or with cav-
aln^ marching at ordinary rate.
The reconnaissance for a column should include besides the road
traveled the nearest parallel road on each side and all connecting
roads * between them. Each mile traversed by the column on the
main road will thus involve 2} to 5 miles of sketching.
If a reconnaissance is to be made when a force is not in motion,
the area to be covered will usually be so large and the time allowed
so short as to make it necessary to combine the work of a number
of sketchers.
78. If any map la available, the area to be reconnoitered should
be outlined on it and subdivided into as many parts as there are
sketchers, the parts to be made equaJU not in size necessarily, but in
amount of work and time required, the important point bdng that
all the parts shall be finished at the same hour.
Each of these parts is assigned to a sketcher, with full instruc-
tions as to the amount and class of work to be done, the scale to be
used — which should be the same for all — and the place and hour at
which the sketch must be turned in. If practicable, each sketcher
should be given a tracing or copy of enough of the map to show the
boundaries of his own task and the adjacent features of those next
to his.
If there is no map, the area may be indicated by landmarks, hut
it will be usually necessary, and always desirable, to go over the
ground and point out his task to each sketcher. When boundaries
are definite there need be very little overlapping. The amount of
reduplication must increase as boundaries become more vague.
79. The area to be mapped may be divided np in any conyenlent
way, but it is best to use roads, fences, streams, or other well-defined
lines as much as possible. Lacking these, compass courses passing
through weU-deflned points will answer.
In a road sketch one man should be assigned to the main road or
that on which the column is marching. Others will be assigned to
such parallel and intersecting roads as it may be necessary to map.
So far as practicable, side parties should leave the main road by an
intersecting road, traverse a short stretch of parallel road, and
return to the main road by another cross road.
80. Compilation — The sketches when turned In are consolidated,
usually by pasting them in their proper relative positions on a large
sheet of paper, or else by pasting them together at their edges bo
that corresponding features will Join. If one of them does not ex-
actly fit, as will often happen, the adjustment is best made by cut-
ting the Bketch into two or more pieces and moving them with respect
to each other so as to absorb the discrepancy. Thus, If a piece of
road is half an inch too short, cut it at tnree or four places on lines
perpendicular to the road and separate the pieces by a sixth or
eighth of an inch. If too long, overlap the pieces instead of sepa-
rating them. If a road or other feature Is out of azimuth, make a
cut through one of its ends and swing it into place. These opera*
tions may be combined. The adjustment is rapid and sufBciently
exact. If a sketch is too much out -to be adjusted by this process,
it will usually be of little value and time will be saved by leaving
it out of the compilation and filling in the gap free-hand, using the
sketch as a guide.
Figure 88 illustrates this method of adjustment.
81. Reproduction. — As many copies of the map will be made as
circumstances may require. The first step is to divide the map into
ao/^Hons of convenient and usually equal size, and make a tracing of
The size of the sections will usually be determined by the
. of reproduction to be used and the size of the apparatus at
Time will be saved if there are not more sections than there
I available to trace, supposing that all the tracers are of ap-
^"^v the same speed. Ii one of them can woric two or three
KSCONNAISSANCB.
Fig. 38
64 EKGnrEEB TIEXB XANTJAL.
times as fast as the average, two or more sections should be re-
served for him, the idea being that the work will be done in the
shortest time if so arranged that all finish at once.
With fairly expert sketchers, it will be possible to have each ink
his work before turning it in. A useful expedient in case of great
haste is to make the sketches themselves transparent by oiling and
fasten them together for use instead of a tracing.
82. The tracing made, further processes depend upon the time
available and whether the work can be done in daylight or must be
done at night.
Of processes requiring sunlight, the most reliable, simplest, and
quickest is the blue-print process.
The prepared paper may be purchased in rolls of 10 or 50 yards.
It should be put up in tin foil and each 6 or 8 rolls should be in a
sealed tin case ; it will then keep in good condition for a long time.
If necessary to sensitize the paper in the field the following solu-
tions must be prepared :
Ounces.
Stock solution A ^^^^f ^^ *r<>^ »°^ ammonia.-- 2
Stock solution B {wl^tlT-^^ i
For use mix 4 parts of A with 3 parts of B.
Unprepared paper may be purchased in 50-yard rolls. To sensitize
the paper a sheet of the desired siae 16 cut from the roll and placed
on a flat surface ; the mixed solution is applied with a sponge to
the upper surface in a smooth, even coat, care being taken not to
wet through to the back of the paper. The sheet is hung up In a
dark room until dry, when it is ready for use. Only enough paper
for a day's use is sensitized at one time, for it does not keep well.
The exposure takes from four to eight minutes In bright sunlight,
varying with the intensity of the light and the transparency of the
tracing. Under other conditions than sunlight a much longer ex-
posure is required ; sometimes an hour or more. Care must be taken
that ;the paper is not taken from the frame before it has been suffi-
ciently exposed. When the margin protruding from under the trac-
ing has a greenish-bronze color, open one part of the back of the
frame and observe the print. The lines should stand out sharp and
distinct on a gray background. Take the print from the frame and
glace it in a tray containing water sufficient to fully cover the print.
;inse it until the lines stand out in clear white, then hang up to
dry. It is to be remembered that the fresher the paper is the slower
it will print and the <iuicker it will wash out ; the older the paper is
the quicker it will print but the slower it will wash.
Additions and alterations may be made to blue prints with a 10
per cent solution of oxalate of potash used as an ink. If it shows a
tendency to run, add a very little mucilage. Common soda may be
used, but the lines have a yellowish cast Instead of the pure white
which the potash gives. Additions and alterations of a drawing are
conveniently made by inking the lines of a blue print with water-
proof liquid India ink and removing all the blue color by the potash
or soda solutions. The black lines then remain on a white ground.
Tbey take well in photographing, and by treating the paper witb
oil, it becomes tran.sparent enough for contact printing, being used in
place of a tracing and in the same way.
Brown prints. — Next in point of simplicity for daylight use is
the brcwn-print process. It is in many respects the most satis-
factory of the copying processes. The paper is pnrckasecl pre-
pared.
After exposure for about two minutes in bright sunlight the margin
protruding from under the tracing turns from its original light
%llow to a reddish-brown color. The print is then taken from tbe
\me, immersed in water, and thoroughly rinsed on both sides,
en the lines come out in perfect white on a sepia-brown ground.
BECOHNAIBSAHCS. e6
It is then immersed In a fixing bath made from the salt which ac-
companies each roll of the paper (2 ounces of fixing salt to 1 gallon
of water) ; this makes the print permanent and also darkens the
sepia-brown color, the lines remaining white. After fixing the print
most be thoroughly washed for 20 to 30 minutes and then hung up
to dry.
The brown color being impervious to light makes this paper very
valuable for negatives wnich may be used to produce positive copies,
either with the blue or brown print papers, yielding an exact repro-
duction of the original in either blue or brown lines on a white
background. In making the positive priots from the brown-paper
negatives the time of exposure is somewhat longer, since the brown-
process paper is not as transparent as tracing cloth or tracing paper.
Rven very fine lines of the original are reproduced with surprising
distinctness, due to the fact that in both manipulations the orgiinal
is in direct contact with the sensitive side of the paper, so that no
light can enter sideways under the lines.
By making several negatives and printing from them simultaneously
the rate of reproduction may be largely increased.
83. For printinfiT hy artiflctal liirltt bromide papers are used.
A contact print from the tracing has clear white lines on a very
dark-brown ground. The contrast is clear and agreeable. Altera-
tions may be made with a sharp red pencil, which makes a legible
line, or by scratching through the emulsion, which makes a white
line. A print can be obtained quickly from the light of three candles
at 12 inches distance.
To develop bronkide prints make a stock solution of bydro-
chlnon, 150 gr. ; sodium sulphite, 300 gr. ; water, 12 oz.
For use, to 1 oz. of stock solution add 1 dr. rodinal and 8 oz.
water ; or, make stock solution of metol, 150 gr. ; sodium sulphite
crystals, 2 J oz. ; sodium carbonate crystals, 3h oz. ; bromide potash,
8 gr. ; water, 20 oz. For use, add 1 oz. stock solution to 4 oz. water.
Acetic acid is used to clear bromide prints after development and
to stop the i^ction of the developer, 16 oz. water to 1 dr. acetic acid.
For flxiner bromide prints use hyposulphite of soda, 1 oz. ;
water, 6 oz. A little alum added to the fixing bath in hot weather
hardens the film.
A bromide print may be made transparent by oil and used for
contact printing by artificial light. It will be better, though not
essential, to secure a paper for negatives thinner than that usually
supplied for prints.
The cycle of operations for quick reproduction by the bromide
process is as follows :
From a tracing or transparent drawing make, say, 3 to 5 negatives.
Make them transparent and start printing from all of them. If the
sketchers are in by 5.30 p. m., the negatives can be ready for printing
by 7 p. m., and after that prints can be turned out at the rate of
15 per hour from each negative. It should not be difficult to have
all tliat are needed for the next day done by 9 p. m.
84. Transfer processes. — With the bectoffrapb the drawing
is made in a special ink and pressed face down on the surface of a
gelatin compound in a metal pan. When the paper is pulled off the
drawing appears reversed on the gelatin surface. A piece of blank
paper pressed on the surface and then withdrawn shows the drawing
direct in purplish lines. Fift3^ to 100 impressions may be taken.
Each print is covered with a thin film of the compound and is sticky,
curly, and very stubborn. The process is at best only a makeshift,
but it is the easiest of all to improvise and the simplest to operate.
For quick work several pans should be provided, as each must be
washed after use and should not be used again until well dried.
The hectograph compound is made of — Parts.
Glue or gelatin , ,^ 100
Glycerin 400
Water 400
94346*'— 17-
M ZVaDTEEE FIELD HANTJAL.
KftQliQ. BO pfli'ts, or Bomi* flwe Inert light-colored powder may be
ttddHd wltU ftdvrt»tftu*«. Tho InKrtHllents require prolonged mixing
)U ^-MiO" {«*,, wUloU iH l)t)Ht oUtalBed in a salt-water bath, 2 ounces
Htilt tu I pint wHter.
TUe ink in luudt^ of - Part*.
NigroHinH lilack - ^-- 1
Ulyi'tu'lu^^ ,._-,„- 4
Wwttu' ^„. ._,_„_ 14
WiMtiOB «!' (1r«wlv\tf ia done with a fresh, clean steel pen. The sur-
face i\t t\w oowpound id uiolntened lightly with a brush or sponge and
aUowt^d to iit»tii*ly ilvy* whon the copy is laid smoothly on face down
ai)d intbbatl to a uuod eontaot throiighout, eliminating all air bubbles.
The p«ii0r U aUowod j't^main two or three minutes and then removed
by »t«rting owe (Hirner and pulling parallel to the surface. The sheets
Ifor imiMH»M»ioua tu^ p\it w\ and removed In the same way, except that
they a»H> Utt o« b\it few seconds,
\VUb tb^ hlMek Miitoeopytttt the drawing is made In a special
iiik »»d tranatdriHHi to a parchment sheet held In a special frame.
'ibU pvA^^'^^j** U fi'W f»^»TO some of the objections to the hectograph,
but M U Wtti^ dittlewlt to work. The copies are Id printer's Ink, are
j)^v\uaww*t» «»d Y^ry aatiafnotory,
H^. Umi«^««iii»«' alE«'t<»litMiK. -Fre<^haad sketehlnj; can not take
tb^ i>lHei» (xf to|H>^r«pby. but It 1$ a valuable adjunet and shoold be
|Mr«^tK*^ bijr ^Ywy aoidler wIm> has any antitnde for pictorial drawing.
A »k;>^t^b dlt|«»r« fr\kiM a photograph onlj In that tt siiows In sharp
vi^^tUv^ a WwU^I ftwwb^r <^X the larjjir^r and eharactertstle features
^iuly s««« aiMl u«der«t^>o«t wtill<^ the ^botofsnipb sihows all details,
IM««^Y oJT tbew !M)^ (ftlnttt^ that tb^v ar^ losft in a mmm of confosed
I^HN^ with i^ iwrm Uiaesw o<bw than tib^ sky lhie» refciliveiy Incon-
a»4CWMi^ All th9> \vsimk K^ a perifv<rt aketeb exist In a pliotograph, bat
cW^ i^^-^tWY ir» <xft«« »e««<$$ary t<> dnd IHhen. If smiglit out and
tii!'«(.'^ kow^-Yvr, a Ipeff<^»«^ sk«^c)3t ir«i»«!ktts;. '!r)ra4£ls$ frosa ptetDgraphs
li» ^^vellMik^ fgp«fcvtk«k
'W^k^ w«^m IVMT ^»i)^ 9k^v4)>lB^ sasMxaN) ^ w» sdnptR^ as msible. A
iA^cl)^lKK>k wiitllt a (f«i!ftYa» cover, CQkvHe^ t'oe a w«t«Htil^hft case, to-
j^M^k^m witk a t<^w^ lK«<^ p«iiMHtf$ R Fv aoNi H. asid pfie«e» of soft and
$i*id ugtWwf *ir<^ t^ wtj««cti;il» fw !j*fcl:b5fu.<.*<K?ey w^jc^ F^wr active llrfd
w<^L'^ ^W Wo^ ^JjtjOiiiij^ be no wltli^ tlMitt oaor be> caorfiMi fin tke pocket
vl an sw^?vi<^?^ W<w«* 4.9*ii u^ftatWelv Iq»^. '■my 5- >y «> tanrilieBL
1^1 «>i>«^»i-v«* .!*!'*{*{/ <>Jc y-U tijiiic i» iitti?«^rtattt — a wek. s knoflt a UD. a
p**ttk— (i«i>tj«vli7i« upon the w»<iJttv»tJ; IHrce towrirtt tlh* mdSiUllle of tlie
tii^lU qI viijw wtiicJi l» (jLettirm ijitfvl \xt)im* H..^i| ctte t)«mrd* <wr sfcgtglibiook
vei'ticail> i>«iw«^ t^ jjye aihi i»uv** it Dacftwarfl '?r fliwrwaafti asBtfl the
tjhtitjt jufcJt tjUs. the tjeidk Loweir the ^oajH? ifijtit tfte- sky IStaie of the
billH ciui t)e i^oeit ;)^ve it^ t<>i.^ t^due. mut witti ;t {)efri:H moirk 9tt that
t}Ul4e tile points (,viH«e»fM>o<iiag te the priiKMtwJ ^iJietrts JUid? weatirants
oi t'le hill forme. If tiesireble the iietml <:ajt De mtived sMfwasys far
vjuouuh to ufiai)le tlie principtiJ heights tu»d (iepressnonfr to* tt* mjuked
on Uie vert'C'tti edge. Hy ijiternectintj re^^rence* tfte ftwatttoiBS can
then he eHHily t^kO-nhliBhtxl on the <»heec. h>*n» tdtese^ ^oilxte 1ft» farsss
can be sk«{i;htid in with inu<,'h M;r»^atw- iieeursey.
l^roceti*] ntix' *♦>' (Jraw fie hjI.'B in our'iue, h^it faiittll?.. wflflt attea-
tjon to «ho larstjr «:«jrvt)e or hunifm at, tii*^. <»?o over Iflksm. aigsaiB
wdh nioi'V) <iare. hrinKin^ out (he ^muitl ir««eg»ilnntit»ts, I3F ajigr p«Mt
oi' 'h« hiH'ifion m visihln. Urnw in IJKhrJy. jind then (}Qini^Q<)9< 1tfiH> sn»>
ei'Hl muts^ oi hillfe hy UrnwinK '^he wHier or hase 11h««^ Steefc noiir for
ilu' >4iu'»af.« v.narHf.im* oi tii« hillB hy trHi-inj? the rnviiw^ UtrRS:. Tfce
Ivimbs* :uk1 ifKiUiillH u^ hioni;nr out hy rrnttinK the tjree meoaidknrs
!jutj -Uiow lorm, \:i <'.hi«mes in •'onn or hi^eakti in the ^romnS mmiBee
' «ni«-.>puuUUm 'iiHHiw in liiti f'oilHKe oi tiie tj-**© Tnneses, wfticn' sftMnr
in Uiti "UstHiuH .ti» in>^muttr lin«s. It iji« more impertanf: oi? it'Vew?
urt4 i^ugiu c4nU UrHWJi, liie ^^euei-nJ character of tjae hiir wciit i*«BiiJ!t.
HECONVAISSAHeX. 9St
X
Add now the foreground crest, and the skeleton of the sketch is com-
plete.
The road and railroad meanders should follow as a rule, and the
fences of the fields. Cultivated land is rendered by parallel irregu-
larly broken lines. Houses, fortifications, trenches, etc., will be drawn
more or less in detail according to distance and importance. Enemy's
lines or trenches even at a greater distance should be strongly marked
by simple black lines. The indication of forests and trees is the most
difficult feature for students. The indications given in the accom-
panying sketches will ^how the treatment in outline work.
Figures 89 and 40 show a variety of forms sufficient for most
localities.
86. Hydroffiraphy. — Depth of water and character of bottom are
determined by sounding with a pole or with a lead and line. Tbe
Monndingr pole may be improvised, or of permanent form. A con-
venient one is 10 feet long, octagonal in section, tapering slightly
from middle to ends, divided into feet which are painted alternately
white, and black or red. There should be an iron shoe at the bottom,
heavy enough to make the rod stand erect when free In deep water.
Such a rod is convenient to use in water 9 feet or less in depth.
If a Bounding lead is not furnished, any compact weight may be
used. The soundingr line should be of braided hemp or cotton,
i to i Inch In diameter, and tagged with cloth or leather. The tag-
ging will depend on the depth to be measured and degree of precision
required. Cloth of different colors may be used for different units,
and leatiier tags may be distinguished by cutting notches or punching
holes in them. The line should be thoroughly wet, stretched, and
allowed to dry. It should then be wet again and tagged while wet.
The zero of the graduation is at the bottom of the lead or weight.
A lead and line are best connected by a rawhide thong passing
through an eye In the lead and an eye made in the end of the line.
Soundings* are usually referred to a plane parallel to the water sur-
face, horizontal except in flowing streams. The plane usually selected
is the water surface itself If stationary, or one of Its positions if
variable, so that soundings will Indicate approximately the actual
depths of water. The elevation of the water surface in the position
selected Is called the datum le^el. If the surface elevation varies,
a gauge rod must be set near the water's edge, and read often enough
to plot a continuous curve of water level. The time of beginning and
enoing a particular group of soundings is noted. The mean elevation
of the water surface during that interval is taken from the curve,
and the soundings are corrected by the difference between the actual
level and the datum level. If the correction to be applied is less than
half a foot, it is usually neglected.
The material of the bottom, as rock, gravel, sand, or mnd, can usu-
ally be told from the feeling of the rod or lead when It strikes. A
specimen of the bottom can be brought up by smearing the end of the
lead with tallow.
A correct sounding is obtained only when the line or rod Is plumb
and straight and its length correct, or its error known and applied.
Except for blunders in reading the line, only one source of error
operates to make the soundings too small, and that is a line which
has stretched since It was tagged or is too long. All other sources
of error make the soundings too large, and hence they are apt to be
so, and actual depths slightly less than those recorded will usually be
found.
To get a plumb sounding from a boat moving through the water,
the lead is thrown out or the pole inclined in the direction of motion
far enough to allow it to reach bottom by the time the boat is directly
over the spot where it strikes. Soundings taken with a line from a
moving boat will always be too large.
The most accurate soundings with lead and line in running water
are taken from a boat floating with the current, with line allowed to
:-Cl
\
\
\
N
X ^ N
\
i;
\
N
V
V - ^
* X -
\
.. i.
BJUJOHVAISSAHCS.
10 ENGINEE& FIELD ICAHTTAL.
hanj; and move with the water. It Is raised only a foot or so between
soundings, Jast enough to clear the bottom.
87. Location of HoundingTH. — The simplest method Is by two
stmnltaneous azimuths from known points on shore. If the sound-
ings are taken on a line passing through one of the points, all azi-
muths from that point will be constant, and one measurement will
soffice. This line is plainly marked by range flags and the boat's crew
tnstnicted to keep the flags in range. Only one instrument and ob-
server are required. This is the usual method for streams and is best
fmr all work where the soundings can be taken in straight lines. Lo-
caRtlons may be made front the boat by two observers taking
simultaneous compass bearings to two known points on shore — see
resection — or by two simultaneous sextant angles. The latter Is less
convenient, as a special protractor is required for rapid plotting.
88. The following notation or its equivalent should be made on a
map or chart containing soundings : ** Soundings are in feet (or
meters) and are referred to the stage of water at (location of gauge)
at o'clock, on the day of . The elevation of this
datum level is feet (or meters)." If the reference plane is in-
clined, add: "and its inclination is in a direction.**
The tint blank is filled with the rate of fall expressed in any recog-
nised way, and the second with a compass bearing.
89. Map readingr is essentially the reverse of map making. In
the latter process ground is measured and studied with a view of form-
ing a mental picture of how a map of it will look. In the former —
map reading — a map is measured and studied for the purpose' of form-
ing a mental picture of how the ground Itself looks. All rules and
principles heretofore stated as to relations between ground and map
are to be nsed in studying the relaticms of map to ground.
The following suggestions will aid the beginner :
R«t« tli« nueridian on the map and associate It in the mind with
tile local meridian. This may be done by turning the map so that the
moridlan wUl p<^t to the north, using the compass as a guide if nec-
essarr. If there is no meridian on the map look for indications of
directloa In local names, or for some road, stream, ridge, or other
feature the general direction of which Is known.
ff«t* tMe aeale of the map. Estimate certain distances, as the
total width or total length or distance between prominent points and
test these estimates by scaling. If there Is no scale look for some in-
dications of distance. It may possibly be found In local names, as
Three MUe Oeek, Two Mile House, etc. ; roads uniformly spaced, as
the Untted States land surveys; city blocks, which are usuallv about
100 yards on the shorter side; railroad stations or sidings, the dis-
tuice of which may be taken ftom time tables. If the map has par-
allels of latitude a good scale may be drawn by assuming fSd miles to
each degiee, or 1.15 miles to each minute. If the ground Is accessible
take two convenient points shown on the map and measure the dis-
tance between them.
If the map Is contoured, mote tke eomtonr Intervals and the
scale of slope equivalents. If the contours are not numbered decide
whicli are the high and which the low ones. Closed contours are much
more likely to be elevations than depressions, especially if several are
concentric A singie clcvs^^ contour may l^e uncertain. Look for indi-
catkiaa of marsh or water Inside of it. If the contour Interval Is not
|r|^Yii it will be difficult to get any due to It unless Isolated elevations
appear on tlie map. If t^e ground Is accessible the contour interval
may be deter*nined br actual measurement of a gradient.
Note all topt^nraphiirft) and cultural signs and associate them in
Hind with their advanta.ses or di;iiadvanta$^^s for military operations.
90. A fooMem ftv^iut^ntly ari^in^r in ni^p reading Is that of de-
tvrmininir iwkat joints are vistMe from a vtven point. A
pcdnt is TisiMe when the gniviient to it. if risime. is greater, and, if
Kniaf; Is saaall^r than the smuliont lo any intermediate point.
Fttr this comparison g-tidio'ts are roiivoRiently represented by the
" of distance in f^^^t divided by the difference of elevation in
BEGONlTAnSAHOX. 71
feet. The point will be visible when this quotient is smaller, if rising,
and larger, If falling, than the quotient for the intermediate point.
Thus, to determine whether the bridge near the Frenchman's (fig. 4l)
Is visible from Atchison Hill or is concealed by intermediate ground,
assume the highest point of Atchison Hill to be in the center of the
1,040 contour and to have an elevation of 1,050. The distance from
this point to the bridge is 5,610 feet, fall 250 feet, quotient 22.4. The
line of sight from this point to the bridge crosses the 960-foot contour
on the flank of Sentinel Hill at 3,060 feet distance, fall 90 feet, quo-
tient 34 ; hence bridge is not visible from Atchison Hill, since the
gradient is falling and the nearer point has the larger quotient.
Working from the bridge the quotient for the whole distance is 22.4,
as before, but the gradient is rising. The distance from the bridge to
the high point is 2,550 feet, rising ; difference of elevation 160 feet,
quotient 16 ; hence, as before, the top of Atchison Hill is not visible
from the bridge, since the gradient is rising and the nearer point has
the smaller quotient.
If one gradient Is rising and the other falling, no computation Is
necessary. A point of rising gradient will hide a farther point of fall-
ing gradient but will not be hidden by a nearer one.
91. Dra-wlngr. — ^The essential requirements of a good topographi-
cal drawing are €Uicuraoy and clearness. By accuracy Is meant a
faithful exhibit of measurements and observations made In the field,
or of data taken from other maps. Clearness involves absence of con-
fusion or crowding, and neatness in execution. Beauty and pic-
torial effect are obtainable by skilled draftsmen only, and while
always desirable are rarely necessary. Persons who are not skilled
draftsmen should not attempt pictorial effect, as It will detract from
accuracy and clearness without substituting anything of equal value.
Avoid unnecessarr iiaste in plotting and drawing. If possible,
take time to check carefully all aKimntfas and distances plotted and
be sure they are exact. There should be no approximation on the
drawing board. Although an observer may have simply guessed
a distance to be 550 yards in the absence of other information the
plotter should be careful to lay It down at exiactly 550 yards.
Start with clean paper and keep it as clean as possible. In the office
wipe off the Instruments before using, especially rulers, scales, and
triangles. Dust the drawing carefully before beginning work. Dust
again when stopping and cover with a cloth or paper. If necessary,
dust the drawing and wash the hands occasionally while at work.
MoJce all inK lines flrm and very blaclc. A drawing to be
made in ink is usually drawn first in pencil, and in such cases a
very hard pencil (4H or 6H) is best. If the pencil drawing is to
be traced a softer and blacker pencil should be used, but must be
kept well pointed.
India ink in stick form gives the best results, but the time re-
quired for proper grinding precludes its extensive use in military
field work. The prepared inaia inks in liquid form are ready for use
and are satisfactory. They must be kept well corked when not
actually filling a pen. If the ink gets thick in the bottle so that it
will not run freely from a fesh-fllled pen add a little water.
The raliniTy or rigrbt-llne pen (figs. 42 and 43) is best for
making lines of uniform thickness. The points must be kept clean,
and when worn must be ground on a very fine stone to the form
shown and to exactly equal length. The points may be closed and
the ends shaped together, which will make them Identical. Then
open the points and grind each on thr^ outside to a proper edge.
Right-line pens are set to make lines of different thicknesses by the
screw D, but the range for any one pen is limited, and different sizes
of pens are made. A very fine line can not be made with a coarse
?en, and it Is difficult to make a very broad line with a fine one.
'he points should never touch. If a line made with the points
slightly separated is too coarse, take a smaller pen. These pens are
jrraded by the length over all. Five inches is a medium and useful
sfse.
EITOQTBER FIELD HAXTIAL.
KECOHJTAZBBANaX.
74 EHOIHBSK IXELD JUJFUAL.
Right-line pens may be filled by dipping an ordinary pen in the ink
and inserting it between the points. A strip of paper closely folded
may be usedf in the same way. In the bottle of prepared ink the
cork carries a small qaill for filling. Take only as much ink as can
be used in two or three minutes. As soon as the fiow becomes the
least sluggish, the pen should be emptied and refilled. To empty or
clean the pen pass a piece of paper (the comer of a blotter is ex-
cellent) between the points.
Tlie adjastingr Mcrevv sltoiild. not lie disturbed while work-
ing on lines of the same thickness. When changing from one thick-
ness to another, open the pen and dean more thoroughly. To reset
for a given thickness draw a short length on a scrap of paper and
lay it alonside of a line of the desired thickness, previously drawn.
The difference will be seen, the pen can be changed and another
trial made, and so on until the lines are matched.
For ruled lines the ruler or curve is laid in the proper position
and the pen drawn along the edge, lightly pressing against it. The
pen should be held with the plane of its points perpendicular to the
plane of the paper and in the direction of motion. The handle should
be slightly inclined in the same direction. For free-hand lines, as
contours, hold the pen in the same way and move the hand so as
to cause the points to follow the line.
In ruling with a writing pen choose one of a size which will make
a line of the required thickness without pressing on the paper. Dip
the point only in the ink. If the ruler has a beveled edge place it
with the top projecting. A curve or a ruler not beveled should be
raised slightly from the paper. The pen should not be inked above
the point which touches the ruler. It is held as described for the
ruling pen. Parallel lines close together may be drawn with one
setting of the ruler by inclining the pen slightly.
Writing pens are best for stream lines. When it can be done, vary
the size of the pen to suit the thickness of line. When using a
writing pen free-hand do as much of the work as possible by draw>
ing the pen toward the body in about the direction of the down
stroke in writing.
For lettering, signs, and all free-hand work with the writing pen,
keep the pen clean and freshly inked and the ink free from dust and
of proper consistency to flow freely without dripping from the pen
in blots.
In using a circular pen (fig. 43), set the legs of the compasses so
that they will span the right distance and the pen point will be
vertical. The lead of a pencil point should be sharpened to the
shape of the ruling-pen points with the flat side toward the pivot leg
of the compasses. When using compasses with pen or pencil, incline
them slightly in the direction of motion and rotate the head between
the thumb and forefinger. Very slight pressure only should be nec-
essary beyond the weight of the instrument.
Figure 46 represents the most convenient instrument for measur-
ing the length of curved or broken lines on a map. The small wheel
is run over the line, and its length in the unit of the instrument is
read from the dial. This length is converted into actual length by
the scale of the map.
92. Papers. — Manila paper of cream or buff tint, usually called
detail paper, is suitable for sketches and drawings which are to be
traced or used in the field. Only the better grade stands erasing
and that i^lperfectly. This paper comes in rolls 86, 42, and 64
inches wide. It may be ordered by the pound or yard.
White drawing paper may be had in rolls or sheets mounted on
muslin or unmounted. Whatman's cold-pressed fine-grain is most
generally useful. It comes in sheets of names and sizes as follows :
Royal, 19 by 24 inches ; Imperial, 22 by 30 inches ; Double Blephant.
27 by 40 inches ; Antiquarian, 81 by 53 inches. Roll papers are 27
to 63 inches wide.
Sheet papers unmounted and kept fiat are best for field topo-
graphical use.
n
n
WORKS AM» JBTRUCTUflCS
CuimI or Ditch
Aqifdiiat or Wmlotpipe
itfinittrt Tumml
Cjum/ Look (jfkii u^9Utm^
>«««••• «»l^M
WMgoBRomdo <|
Trail or Paib
JWHUW -
0—4
\
:X««-*SBSiSSS£<
Qb «IIIAir-M4M »MS .
lUilnod of MmfUtid
for StngmTHoli^
DottkhTnittk
»■ > * » I t « t t I I !■ I t
— » Kui'il ii>l»»»»Mi^»^il»i^ii^1»r^
RMilrooOB <
JmxtMpooUiOB of.
Bhatrie
<Vi'^>**N^*iK*i**
■ KM Ml >>>»»*<»«» nil II mi
i;» WogOB JiMiF •r SCTMl SiMm Ml—irie
L
lUtWm ■ ~ » « I t »»-='-=='"T<i III*
RMilrott€l SUUion of any kind. , ,
r
Symbol (modifiti Mow) ^ ^ ^ r t t r t r
Along rood
Toiograph line <{
Along rood
{BmoU-aooSo mopo)
Along troa
Ehotric Power Transmission Line
I I 1 I I I T 1
T — I — I — I — I — \ — « — r
Fi(. 48
WORKS AND STRUCTUneS
OtMTtl Symbol ..j ^
i
oh*rt«5«v«tft«nn»/op«a) \ ,
3- —
Tnut {W.Wood: S.St— II
■ —
foot - „S«Btrt^,W, lirt
II ■
:.^ 4«>*-IW«4 SO
|||£^
x«, SS-JiK!"
BL
,--.- ~ ■-
{OtaumI Sywbol
(or WftontaiArtBitry)
WORKS AND STRUCTURES
BaikHnga ia gaotrtJ ...
Ruins
Chiirah _
HeepilMl
ScAooIbouM
Post Office
Tol9grnph Offho -
Wtt^rworkB
Id -■■■
GMy. Town, or Villtg*
City. Town, or ViOtgm (jtnrtHi^
City. Town, or VWmgt \ -^ 5^
\oanr Towns
Fig. tW
WORKS AND STRUCTURES
Cemetery
l«r;
Mine or Quarry of eny kind {or open cut) *
Prospect - X
Shaft
Mine Tunnel
'\Op9ning
[Showiag direction.
on Wells .V
Oil Tanics iMkbrmviMtion OT)
Goice Ovens..
F^ncm •fkny kind^.
(or b9Mrd fenom)
Stone
Fences < Worm
Wire
Hedge
■ O II ■ ——»»«»— —^—*>»
/ >«fs/W%^V«- .'^/S^V•^-^-'V^'
BTkmd Smooth
X— y— X— x-x-x o— •—•—•-o
...fi n <■•■%■-.:> 'r ^ 7» CjO *> -o •>*\
Fig. 51
BOUNDARIES, MAI^KS. AND MONUMENTS
NMianal State, or Province Line.
Couniy Line .» „
C/wff Township, DiMiriat,
Preoinct, or Barrio
RoeervmUwi Line
Lond'Orsait Line ,
City, VWoge, or Bereugli _
Cmmotmry,. Small Poric, etc
• ' « m.
Towneliip, Section, and Quarter Seatien
Lines (my mm for tommaidpilee aha; any
two for towBthip wad ooethn Vboo
Townsliip and Section Corners Recovered ^^ ^^ ^
Boundary Monument #- . _
Trianguiation Station _ 4
Bench mark V*
1232
CA S. Minora! Monument.
Fig. 52*
ORAINAQ&
Streams in general
Intermittent Streams
Lake or Pond in genersl
(with or without tiot, wamrJUniag..^Hti.)
Salt Pond (brokw ahxmSSm^mmmmuBi^
JntGTBoMtiBiii LmJcb -or f^ood-
Spring.
-^ N-V**- ■ •--fcwV^--- -,-•. -^r %^A>« «i^^V - •%*^*- - <l *».•.«<« •-■maf*
^ ^^:^
Fans and
/
Gotti\
(oi
or $» bohw)
GlaeiarB <
Form Unoo ohowing flow.
@'ZM2-^^
<Slmwaby eeoMari, Arm Hat, ar tlitdini
fl>»cky (eruM csntottn) .. .
\ptlttr Huh nelcy (or in* ei
....^
LAND CLASSIFICATION
fMttrth m fnTtJ ior Fnsh htMrsh)-
StM
Manh i
Wooded
vCxi^rtM Swtanp,
-"^a Tnr'le— ^' ^: -T"-
.37?;
rnc
3173
.MH
as:
"■ - -'p--
3E
TJicr
'..ly '41^
:3£r
— "-
aiKl
.lat
"^ :£^i -fe f^'-f^^^
M^^^^:^^^
.';■-»•■=.;
-/-^
IVdtfds 0/ any ir/Atf (or m sAown ft«l»w)
IVotfds of any kind ior Bntul'UMvd Tr—)
i/-y.
w
?•-■■ ' -
r'
^w>;;>:s
c:b
">^
«i
«,i
--•.•..
<%'
^.
■ - . .' . . ef.
^
< J
<v^
-n
. <^
f »
^•:-
.4" •'
^•^ 'A"
■ •
•<^j ^^"
. ', 1 •. , ^ r\
'"/
?5:,
rd
LAHD CUMMff^flCATlON
/%•• (•r Nkrrwv-lMVMf 7>«w)
.»
7~r
«.. * ^
Adn
P!a7a««o
^.^^''J:'.^^
^^^ >
^ ->5t^.
'4
r^*'^^
fi^f^
Mmngnve
Bmmboo
i'^ •
* *-: + .'
♦ ■^ -
-♦ -
*»■ ,4 * + + -I-
Pig. 56
_ *
ON.
rr^
-V ■'V
«^3.
J? .^0
J"/
> '-V <,
'^ ^
<Ji> nC)
* ^ < » ^ ^ *
^ d ^ O
^
3^ ^ Ci 0
« 0 €* -;^
<^> ^' <s? e
^^
4^ • ,*- >
N^.*
.\M',
.''' .sV
.%•*!
*'.V-
>^iH
lANO dtAARHVCATIOM
CuAh«WFiW*/j)
■ fl
= . ;
I ^
eSVTRUCTIONS
HYOAOOHAFHY, DAN«fill». 0«STJtUCTION«
OonJ R%9fs.
K%ip
Eti Grass
_^^^^^-
Reckundsr wMtsr
•*■ t.
IteokMWMSh (tmyaiMg9cfamtUt^ *
M^ek whose posWoa is doublfid
♦ PD
Rook whose existence is thubtfui > jp/)
Overfaiis and Ti<i9 Rips
>•«•«•-*•
Limiting Danger Line
Whir JpooJs and SMfes '....'. (^ (g)
Wreek ef any kind (or SubmTg9d D^fUct) -^
Wreak or Dereliot.nat submerged ^
Cmbie iwith or without httoring)
Fig. 60
HYDRO'
Shoreli
kn
I km .
or " ' n »
Sib sb
^ HM, lib 4Ht. /t lUihU gn. gr—n, br> Atpwa.
^ *^ ««i MftTM. Fiy. roc*y, a<fe athky,
^ N«^ 4flNA s</. Stiff, oMl. c^lemnoM. tf«o.
fit fVnty,gty. gritty, grd.grwmg.
ru. *1
HYDROOl?AFHY. DAtMERS. OBSTTRUCTIONS
J Fathom or 6 Foot Line _
2 Fathom or 12 Foot Line
5 Fathom or 18 Foot Line
4 Fathom Line
4% Fathom Line
6 Fathom Line
6 Fathom Line
10 Fathom Line
20 Fathom Line
50 Fathom Line
40 Fathom Line
60 Fathom Line
JOO Fathom Line
200 Fathom Liiie ..
300 Fathom Line-
600 Fathom Line
1OO0 Fathom Une
2000 Fathom Line
SOOO Fathom Une
■-t^***-^--- *-"*•» f ■•• ••*•*-• »B«%B*«^*»«ah4. •a^a^.a ••«-■•••*«■
Pig. «2
o .^:*o^4* ETC.
LSS. (TJ
<ifamaU x Jtjt
m •
®
and Wirmhas
4-
ft
®
lE •
■n. 1 I 1 I I X
>^,^^«^ <»»iMa t> dotted lines
.^'^x^M*f^9^ y^ektfng to Lights
to. "iK^.^^^ ^ •*«^ '^ /hwAw. Sac. sector. Rev. rtv»/v-
^ , XV*<» t ^^ V varrM by, Oip. group, Ooc
\ ju.iu.r»ri ^^ tS^rMiing. m. milos, ndn. minut—.
AIDS* TO NAVfQATlOW ETC.
[Buoy of Any kind (or R9d Buoy)
BUck.
Buoys <;
Stripod horizonUUy
Striped vorticAlly .. .
Chockered
Perch And Squnn .
ProhmndBMU
I Boll {or u90/int/our symbols with,
word'' boll")
\Ughtod
• • • •
AM***
Whistling {or uoo first four symbols ; ; ; ;
w/fft wo/itf " whatUng ")
& A b &
• • • •
Spindle or Stdke (Mddword"spindlo" i
,jf 9PAC0 mUows)
Abbreviations relating to Buoys
C. ctn, N. nun, S. spMr, H. S. horizontad Mtripos, B. bUok. R. rod.
W. white. V. S. vertical atripes. G, green, Y, yellow. Ch. oheckered.;
Anchorage \
Of any kind (or for Urge vessels)
For smell vessels
■I
Mooring Buoy
V*J
Range or Tracic Line
Fit,. ^
SPCCIAi. MfLlTARV SYMBOLS
Regimental Headquarters ImI
2B
^rigSide Headquarters woitac
Division Headquarters stii^sc
Corps Headquarters "W
infantry in line
c:3
Infantry in column ' S
Cavalry in line i^a
Cavalry in oolumn • S
Mounted Infantry 'i^
Artillery ,. i iji i|i i i|i
Sentry 6
Vidette ^
Pioket, Cavalry and Infantry isk *»
• • • • '
Support, Cavalry and Infantry Jfm c*3
Wagon Train
A^utant General
Quartermaster
Commissary
Fig. 6t
SPECIAL MILITARY SYMBOLS
MedicMl Corps p^
OrdMLiiCB O
Signal Corp^ - P
Engineer ioips \ ; :, ^ ^ , ; M
Gii» a#tfery .....,, ... , ,. , ^ ^fp^
< *
Mortar Bkttery " !.
-' » '• ■■ ■ .
Fort \,' . . •' t- ,
\ Ttv9 plAo to 6« sb9wn if known <.
Redoubt } K
O 0'
AAA
Cawp AAAA
Battle . .., , _.... * ^^
Tr&neh.
Whm CQlor is tjaed-exeeute the f6UoyiHn\ ih re^
- . t. " >
Abaitis ^ ^if ^^^
Wire Bntgn^ihem
Palisades 1
. \ '' *
Contact mines o o o
Controlled 'min4e ' o^^^^V^
Fig. 65 a
Sf
LrrTERlNG
CIVIL DIVISIONS
Staters, CovavtiefS. IkywThslvtps, Capitals and
PrvrvGipcd, Cities fcJl capital laUerBf
ABCDEFGHIJ
KLMNOPQRST
UVWXYZ
Towns azLcL VUlage^s (with. Cap iruiraZ»/
&b cdef jghrjldmnopqr stiivwxy z
HYDROGRAPHY
Lake's, Hirers cuvcL 3a^s (all o€Mpital IMm^)
AB CDEFGHU
KLMNOPQRST
UVWXYZ
Creeks, Broohs, Springs, small Lakes. BotvoLs,
Marshes and Glaciers fwitfv Cap. ifyitiaisj
abcdefghyjcbruiopqrvtuvwjcyz
Fig. 86
tiCTTERIMS
MoztTvtcuTvs, Flatemat, £ins0 of Obif^
euui Ccmyons fall oapital lettesrs )
ABCDEFGHIJKLMNOPQRSTU
VWXYZ
Perciks, smajl J&tl&ys^ Canyons, Jslands and Foints.
(with €hp. mxtuda)
abcdefgh ij4( (hi nopqrstik V wxy z
PUBLIC WORKS
Itcuilroajd&, IRcnivels, 3ri$lgefS, Ferrie^, VajgoTv-ToaxLs,
TrailB, Fords <uuL Jhcms (oapitnU <mJy)
C ONTOUR NTJMBE RS
t2S^Se7S90
MARGINAL LETTERING
AB CDEFGHI JKLMNOPQRSTU
VWXYZ
^ (wHsfv Ccip. tnitucda)
a bcdef^h ij kl m nopqrstu vwx^ 2
1234-567890
Fig. 6# a
k.CTTEf«M€
NanfS of oMtur^lJuid /9Atur98, vftrtH^i Mtfring
N»mes of fMturtl wmtmr f0*tur9». atMtithig htlTing
Thicktiess o/ hUer f o/* h^hi
Slope of letter 3 parts of beae to 8 of height
AUTHOftlZeO ASBREVUTtONS
A
Arroyo
US-S
. Life Saving Station
abut.
Abutment
L.H.
Lighthouse
A.
Arch
Long.
Longitude
b
Brick
Mt.
Mountain
B.S.
Blacksmith Shop
Mta.
M«i»n«»ins
bot.
Bottom
N.'
North
Br.
-Branch
n.f.
Not fordable
br
Bnd^tt
p.
Pier
C.
Cape
pk.
Ptank
cem.
Cemetery
PO.
Rost Office
con
Concrete
Pt.
R:>int
cov.
Covered
<4P
Queen- post
Cr
Cre«k
R.
River
cut.
Culvert
R.H.
Roundhouse
D.S.
Drug Store
R.R
Railroad
E.
£»9t
3.- .
Sooth
Est.
Estuary
s.
Steel
f.
Fordable
S.H.
School House
Ft.
Fort
S.M.
Saw Mill
G.S
General Store
Sta.
Station
^'•-
Girder
St.
Stone
G.M
Grist Mill
str.
Strea m
i.
Iron
T.G.
Toll Gate
1.
Island
Ires.
Trestle
Jc.
Junction
tr.
Truss
Wp.
Kin^-post
W.T.
Water Tank
L.
Lake
W. W
Waterworks
Lat.
Latitude
W.
West
Ldg.
Landing
w.
Wood
Fig. 67
BECOlTKAISSAirCE. 97
93. If a blot drops on the drawing take a piece of blotting paper,
tear a corner or edge to expose a fresh snrface, and hold it in the
blot without touching the drawing until the surplus ink Is absorbed.
Then press a dry blotter firmly on the spot and let It dry thoroughly
before attempting to erase. A piece of newspaper may be used
Instead of blotting paper, but should be sllshtly moistened to hasten
the absorption. For a large plot several pieces may be required.
94. BTaaers for ink are or steel or rubber. A steel eraser or pen-
knife must be very sharp to give good results. An eraser of gritty
rubber Is most generally used. It is best to use an erasing shield
of thin metal or celluloid (flg. 44), which exposes the area to be
erased through one of the openings and protects the rest.
95. Tracing: linen is usually dull hack, having one side glazed
and the other dull. Srasing can be done on the glazed side only.
The glazed side is used for ink and the dull side for pencil work.
The glazed side requires preparation before use to remove excess of
giramn, which prevents ink from running well and clogs the pen.
ubblng hard with fresh blotting paper Is the simplest method.
Tracing: paper is alike on ooth sides. It will not erase. Most
varieties are less transparent than tracing cloth.
In tracing it is helpful to use a dull-painted Instrument In the
left hand — a stylus or top of a penholder — ^to press the linen against
the drawing at the point where the pen is resting.
96. Conventional aisna. — The symbols or signs used to repre-
sent topographical features are designed to be rapidly made and read-
ily understood, and to resemble or suggest the actual features they
represent. Multiplicity of signs Is not desirable, and a verbal desig-
nation or description of the features is often more intelligible and
more quickly recorded. For instance, it Is better to xrrite the names
of the growing crops of a district, as tobacco, corn, or cane, than to
cover the entire area with a symboL Another method of expediting
mapping is to surround an area with a narrow border of the proper
sign and leave the middle blank.
The conventional signs adopted In 1012 and published to the Army
in pamphlet form are shown in figures 48 to 67, inclusive.
The adaptation of conventional signs to the size and scale of the
map is accomplished in part by varying the boldness of the pen or
brush strokes and in part by wider spacing of them. The strokes
must never be so small as to render the sign illegible and never
larger than can be easily made with a medium pen. The object is to
produce a result which, while distinct as to conventional meaning,
shall not be so heavy in general tone as to catch the eye, or, what is
especially important In military maps, to obscure any additions which
may be made. Topographical signs should be perfectly clear when
looked for, but not obtrusive.
As a rough guide, it may be stated that the signs shown In the
plates are about right for continuous areas of 3 square inches or less
In maps of scales of 2 or 3 inches to the mile. If the map areas are
larger or the scale smaller, the signs should be llghtoned some, but
not much, by making the strokes smaller and by spacing them wider.
Some examples of good maps show the meadow sign*, for example,
with two or three elements to the square inch. For very large scale
maps and for field sketches the strokes may be made heavier and the
spacing in them close. These remarks apply only to cultural signs,
and a few others the significance of which is Independent of size and
shape. All natural or artificial features in which size and form are
in any way material should be drawn with as much regard to th«
scale as practicable. This becomes more important as the scale is
lar<'er.
It may, therefore, happen that the same feature will be differently
shown on maps of different scales. This is well illustrated in the
case of streams. Figure 53 shows four signs for streams. On a
large-scale map, say 1 : 1,000, a rivulet a few feet wide would be
shown by the second sign, while on a scale of 1 : 1,000,000^ a stream
1 mile wide would be shown by the first sign.
94346»--17 6
08 ENQIHSSB FIELD XAVTJAL.
On civil maps explanatory matter is nsnally confined to notes. On
military maps much use should be made of explanatory matter in the
body of the map relating to single features. The design, material,
and dimensions of bridges may be indicated ; the height and width of
channels and dimensions of locks and canals may be given ; the width,
depth, and character of streams may be indicated, and otiier data of
tactical value may be set forth. This method of expression will be
more freely used as the maps or sketches are of less permanency or
more historical in character. For maps designed for permanent use,
or for use at an indefinite future time, this method must be employed
with
…[truncated]