MAP READING AND
FIELD SKETCHING
T h e U s e o f the Protractor and Field
Compass and Reconnaissance for
Battalion
/
Intelligence
WQQiLl
qL
COPYRIGHxl
Compiled and written by
CAPTAIN A. S. KBIGHLEY, M.C.
A.M.F.
Late G.S.O. 3, 4th Div. A.I.F.
Bde. Intelligence Officer, 3rd Bde. A.I.F.
By
the
Same
Author
The Essentials of Training
for the
HOME •GUARD
Weapons their Potentialities
and Limitations
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Guerilla Tactics
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AND BOOKSELLERS
Price : One Shilling
Map Reading and
Field Sketching
The Use of the
Protractor and Field Compass
and
Reconnaisance
for
Battalion Intelligence
•
COPYRIGHT
1942
Compiled a n d written, by
C A P T A I N A. S. KEIGHL.EY, M.C.
A.M.F.
L a t e G-S.O. 3, 4th Div. A.I.F.
Bde. Intelligence Officer, 3rd Bde., A.I.F.
MAP
READING
Military m a p s a r e topographical m a p s to which
additional i n f o r m a t i o n of a military n a t u r e h a s been
added.
T h e five essential f e a t u r e s or divisions of a topog r a p h i c a l m a p are:—
(a) Tile title showing the location of the country
represented, w h e n t h e m a p was made, who
m a d e it, etc.
(b) Tlhe conventional signs, by m e a n s of which
various f e a t u r e s such a s roads, streams, towns,
etc., a r e represented.
(c) T h e pointers or a r r o w s by m e a n s of which t h e
m a p can be properly oriented a n d directions
determined.
(d) T h e scale, which shows relations b e t w e e n
lengths or distances as they a p p e a r on t h e m a p
and the a c t u a l distances on the ground.
(e) T h e relief, or the method of showing t h e shape,
slope and height of t h e hills a n d valleys.
Most systems of projection, or methods adopted to
show on a plane s u r f a c e t h e meridians or parallels of
t h e globe, require t h a t the meridians a t t h e top of
t h e m a p be closer together t h a n a t the bottom f o r
Northern. H e m i s p h e r e a n d vice v e r s a f o r Southern
Hemisphere—such m a p s cannot be fitted exactly edge
t o edge so a s to lie flat, b u t m a y be m a d e to do so,
by leaving a small space b e t w e e n t h e vertical edges.
I n other cases t h e edges of t h e m a p a r e not based
o n latitude a n d longitude lines b u t a r e perfectly
r e c t a n g u l a r . T h e r e f o r e t h e meridians and parallels
shown will not be parallel to the edges of the m a p .
I n d e x m a p s show a large section of country a n d
outlines of sheets with n a m e s a n d numbers.
On most maips t h e n a m e of adjoining sheet is given
b y small index m a p in m a r g i n . T h e date of issue f o r
2
military m a p s is important—in war, m a p s a r e issued
daily f r o m aeroplane photographs.
M a n y have list of conventional signs.
O n a n y m a p m a d e a balance m u s t be sought bet w e e n clearness a n d legibility and the a m o u n t of det a i l t h a t c a n be shown, b e a r i n g in mind the use t o
•Which t h e m a p h a s to be put.
Relief
T h r e e methods—hachures, contours and shading.
T h e method adopted to show the Relief m u s t indic a t e clearly three things:—
(1) T,he shape a n d size of hills;
(2) T h e slope;
(3) T h e height of ground.
T h e c o n t o u r system does all these three with t h e
h i g h e s t accuracy of any method b u t it is h a r d e r t o
u n d e r s t a n d — m o r e difficult to visualise w h a t t h e
g r o u n d looks like — b u t accuracy is essential a n d
s h a d i n g m a y be used in conjunction.
T h e h a c h u r e method is f r o m 16th and 17th Century
— s h o r t shade lines r u n n i n g down slopes showing
direction w a t e r will flow — slope is indicated by t h e
t h i c k n e s s a n d spacing of lines — i.e., a steep slope is
shown by heavily inked lines close together. Lightly
s h a d e d portions a r e gentle slopes — level a r e a s l e f t
w i t h o u t shading. E x a c t height of ground is shown on
hac-hure m a p s by spot levels or height m a r k e d thus,
"103," "153." T h u s hills became k n o w n as "Hill 60"
etc. I n n a m i n g hills thus, however, locality m u s t be
given a s o t h e r hills are also m a r k e d similar heights.
H a c h u r e method common in E u r o p e a n maps. " C a r t e
d e P r a n c e . " German, 1:100,000 and British Ordnance.
The Contour System
T h e contour s y s t e m is used toy most countries. A
c o n t o u r line m a r k e d m e a n s so m a n y feet above zero
3
level or datum—which is usually shore or sea level.
Contours a r e sometimes described as successive
shore lines.
Contours alone will not give t h e exact height of a
hill. These, in i m p o r t a n t cases, a r e s h o w n on t h e
m a p by points or spot levels such a s 135. W h e r e no
spot level is given, say we w a n t to estimate t h e height
of a hill where t h e contour below t h e top is 130. W e
k n o w it m u s t be less t h a n 140 for 130 is t h e h i g h e s t
s h o w n so we can e s t i m a t e 135.
Depressions a n d basins below t h e ground s u r f a c e
a r e shown by closed contours j u s t like hill tops b u t
every contour is not numbered. Therefore, w h e n a
contour shows a depression level, s h o r t lines a r e
d r a w n on t h e inside of t h e "depression contour"
(pointing down slope). A special h a c h u r e sign is also
employed f o r cliffs, s a n d dunes, etc., shown by fine
stippling.
T h e layer s y s t e m shows relief: Cut t h e contours
out on cardboard, of equal thickness corresponding
to t h e V.I. T r a c e contours off m a p a n d then w i t h
blue carbon copying s h s e t t r a c e on to cardboard, cut
board to shape of contours a n d place one on top of
each other, f a s t e n i n g on to a base—there you h a v e a
relief map—if covered with modelling clay it becomes
a model.
Reading Contours
T h e relative position a n d c u r v a t u r e of contours a f f o r d s clear evidence of t h e shape of t h e ground. T h e
m a i n conclusions which m a y ,be d r a w n f r o m their
shape and s p a c i n g a r e h e r e considered. A comparison of the ground with a well-contoured m a p will
s u g g e s t others. This subject m u s t be studied w i t h
care, as he who cannot u n d e r s t a n d the evidence of
contours will u n d e r s t a n d neither t h e m a p nor t h e
c o u n t r y it represents.
An expert m a p r e a d e r will seldom consult contour
4
n u m b e r s or spot heights f o r t h e general purpose of
distinguishing hill f r o m valley, because t h e r e is generally clear evidence of t h e slope of t h e g r o u n d in
s t r e a m s , lakes and ponds. A s t r e a m m u s t be in a
valley a n d a l a k e or pond in a depression. It is this
simple f a c t t h a t m a k e s a study of t h e d r a i n a g e t h e
first step in t h e examination of any map.
Uniform, convex a n d concave slopes a r e represented as follows:
i. W h e n the contours a r e evenly spaced the slope
represented is uniform. (The slope of river
a n d s t r e a m beds is generally u n i f o r m except
n e a r t h e source).
ii. W h e n the spacing, reading f r o m high to low,
decreases t h e slope is convex. (The top slopes
of hills a r e often, though not always, convex.)
iii. W h e n t h e spacing, r e a d i n g f r o m high to low,
increases, t h e slope is concave. (The bottom
slopes of hills a r e generally concave).
U n i f o r m a n d concave slopes viewed by a n observer
f r o m above, a r e visible t h r o u g h o u t ; in o t h e r words,
t h e r e a r e no concealed portions to f o r m "dead
ground," convex slopes, on the other hand, imply dead
ground.
Contours d r a w n close to each other indicate a steep
slope; t h e f a r t h e r a p a r t they are, t h e more level is
t h e ground.
I t is i m p o r t a n t to realise not only the capabilities,
b u t also t h e limitations of contoured maps. A smallscale m a p h a s no room in which to show the n u m b e r
or t h e accurate- shape of contours characteristic of a
l a r g e r scale. If t h e V.I. is 50 f e e t (as on one-inch
m a p s ) , f e a t u r e s of real tactical i m p o r t a n c e (but of a
lesser height t h a n 50 feet) m a y not be shown. On
quarter-inch m a p s t h e V.I. is generally 200 feet, and
comparatively large f e a t u r e s a r e not shown.
Horizontal Equivalent (usually w r i t t e n H.E.) — is
t h e distance in plan between two a d j a c e n t contours.
5
Vertical I n t e r v a l (usually w r i t t e n V.I.) — I s the'
difference in level between two a d j a c e n t contours.
Slopes and Gradients
T h e slope (rise or fall) of the .ground between a n y
two points m a y be expressed a s a n angle — e.g., 5.
degrees — or a s a gradient — e.g., 1/15. T h e slopes
of r o a d s a n d railways a r e usually expressed as gradients, or as a rise or fall of so m a n y units in a given
distance.
T h e g r a d i e n t is t h e t a n g e n t of t h e angle of slope
(
"
)
\H.E.
/
and the relationship between slope V.I. and H.E. m a y
be founded on t h e f a c t t h a t t h e t a n g e n t of 1 degree*
is approximately l / 6 0 t h (or, w h e n t h e slope is 1 degree the g r o u n d rises (or falls) one foot in a distanceof sixty feet.
1
60 feet.
T h u s a slope of 1/20 feet equals 3 degrees, i.e.—
20 feet
One word of caution m u s t be added. T h e V.I. is.
usually expressed in f e e t a n d the H.E. is generally
m e a s u r e d in yards, but the rules given above a r e only
t r u e w h e n both a r e m e a s u r e d in t h e same unit.
Examples of Working in Slopes and Gradients
A certain M.T. Column, fully loaded, cannot climb
g r a d i e n t s steeper t h a n 1/5, and it is required to find
f r o m the m a p a practicable r o a d f r o m A to B.
A convenient road goes up a hill on which contours
(V.I. of 50.feet) are, a t the minimum, 100 y a r d s (®v300 feet) a p a r t . W h a t is the g r a d i e n t ?
6
V.I.
The
gradient
=
50
=
H.E.
300
a n d t h e road is t h e r e f o r e passable.
=
1
6
Direction
T h e direction of t h e north is given by an a r r o w or
pointer. W h e n parallels of latitude and longitude a r e
shown by lines the l a t t e r a r e true meridian n o r t h a n d
south lines. W h e n no other i n f o r m a t i o n is given, it
Is s a f e to a s s u m e t h a t t h e top of the m a p is n o r t h a n d
t h e edges n o r t h and south lines. T h e compass needle
r a r e l y points to the north.
T h e divergence of t h e compass needle f r o m t h e t r u e
n o r t h is t h e error k n o w n as declination — this is
b e c a u s e of t h e magnetic attraction a t t h e poles, a n d
these poles do not coincide with the geographical
poles. T h e compass needle points to the m a g n e t i c
pole a n d t h e angle between t r u e a n d m a g n e t i c varies
according to time and place (magnetic variation).
I n P a r i s in 1580 the declination w a s
deg. E. of
true—in 1810, 22i deg. W. of true.
I n A m e r i c a there is a curving line r u n n i n g south
passing t h r o u g h the G r e a t L a k e district, leaving t h e
coast in Southern California. At any point on this
line, t h e declination is zero and the compass points to
t h e t r u e north, w h e r e a s a t New York, east of this
line, t h e compass points west of north and a t S a n
Francisco west of this line, "agonic line," it points
east.
W h e n using a m a p in t h e field, it is necessary t o
t u r n or orient t h e m a p till its sides point n o r t h a n d
south, so t h a t objects on the ground a p p e a r to you in
t h e direction as shown on t h e map.
T h e direction of t h e north and south line or meridian on t h e ground can be determined b y using t h e
compass—release the needle and hold compass hori7
zontal. T u r n the box till the n o r t h end of the needle^
reads the declination, t h e n a line t h r o u g h the zero of
the scale of t h e box will be t r u e north a n d south.
If a compass is n o t available, use a watch. I n th&
N o r t h e r n H e m i s p h e r e point h o u r h a n d a t Sun. A line'
between h o u r h a n d and 12 noon' gives South.
la
Southern H e m i s p h e r e point noon a t Sun and a line
between 12 a n d h o u r gives north.
T h e P o l a r S t a r a n d two pointers point north.
S o u t h e r n Cross, prolong t h e g r e a t e r axis f o u r and a.
half times to obtain South.
Bearings
A b e a r i n g is the angle m e a s u r e d clockwise f r o m a.
certain fixed line to any line in question. T h e fixed
line m a y be the true north, grid n o r t h or magnetic:
north.
Definitions of True, Grid and Magnetic
North
B e f o r e proceeding f u r t h e r , it is necessary to u n d e r s t a n d t h e m e a n i n g of the terms, true north, gridl
n o r t h and magnetic n o r t h .
1. T R U E N O R T H . — T r u e north m e a n s t h e direction;
of t h e n o r t h pole f r o m t h e observer.
T h e north pole is a point, a n d the e a r t h is a sphere.
I t is t h u s evident t h a t t h e m e r i d a n of an observer im
E n g l a n d , and t h a t of a n o t h e r observer in, say, F i n l a n d , will not be parallel s t r a i g h t lines. T h e y wilt
converge i n w a r d s t o w a r d s t h e pole, where t h e y will:
meet.
ii. G R I D NORTH.—Grid n o r t h is the direction im
which the grid lines point t o w a r d s the top of t h e map.
To be of value a grid m u s t be rectangular. I t is.
obvious t h a t if t h e grid lines everywhere point to
t r u e north, the grid cannot be rectangular. It is usual!
to m a k e one grid line coincide with a meridan. On-,
t h i s " s t a n d a r d " m e r i d a n t h e grid points to the truer
8
n o r t h . All other vertical grid lines a r e d r a w n parallel
t o it, a n d do not point to the t r u e north, but in each
case to a different a n d imaginary point called t h e
;grid n o r t h .
T h e angle between grid north a n d t r u e n o r t h is
.known as "the angle of convergence," a n d it is evid e n t t h a t this angle increases t h e f a r t h e r t h e grid
d e p a r t s f r o m the s t a n d a r d mei'idan.
111. M A G N E T I C NORTH.—Magnetic n o r t h is t h e
.direction in which the compass needle points (una f f e c t e d by any local a t t r a c t i o n ) ; i.e., t h e direction of
t h e m a g n e t i c pole a t a n y point. T h e magnetic north
pole c h a n g e s f r o m y e a r to year, a n d t h u s t h e magnetic variation, which is the angle between t r u e n o r t h
a n d m a g n e t i c north, varies f r o m year to year a s well
as f r o m place to place.
I t should be noted here t h a t (a) every o r d i n a r y
c o m p a s s h a s its own individual variation which will
•differ by a c o n s t a n t a m o u n t f r o m the local m a g n e t i c
variation, and Ob) t h a t compasses a r e affected b y
local a t t r a c t i o n , such as a hill in which m a g n e t i c
i r o n o r e is to be found, guns, tanks, etc. Thus, before
u s i n g a compass f o r accurate work, certain precaut i o n s m u s t he t a k e n .
To test the individual variation of t h e compass
p r o c e e d a s follows:—
1. I d e n t i f y on the Map and Ground, t h e standpoint
"A" a n d some d i s t a n t object "B."
2. F r o m m a p with p r o t r a c t o r find Grid (or True)
b e a r i n g of "B."
3. W i t h compass, find compass bearing of "B."
4. F r o m the Grid (or True) and Compass Bearings,
find t h e compass variation.
5. C o m p a r e t h e compass variation with local m a g netic variation.
(a) If they coincide, t h e compass is correct.
9
(b) If different, the compass will have an individual variation of so m a n y degrees E a s t or
W e s t of Magnetic N o r t h .
Conversion of Bearings
T h e b e a r i n g of a n y object on a m a p m a y be expressed in one of t h r e e ways, i.e., with reference to
t h e t r u e north, grid n o r t h or magnetic north. On a
gridded m a p all bearings m u s t be given with r e f e r ence to grid north, and not to t r u e or magnetic north.
Gridded m a p s show in t h e m a r g i n t h e angle b e t w e e n
grid n o r t h a n d m a g n e t i c n o r t h with a n additional n o t e
s t a t i n g t h e angle between t h e grid n o r t h a n d t h e
t r u e n o r t h f o r t h a t sheet. This enables t h e user of a
m a p to convert a b e a r i n g given with reference t o
magnetic or t r u e n o r t h to grid north.
Supposing t h e variation of a compass in a p a r t i c u l a r
locality to be 20 degrees West, a magnetic b e a r i n g of
20 degrees will give t r u e N o r t h . Similarly, if t h e
v a r i a t i o n is 20 degrees E a s t , a magnetic b e a r i n g of
340 deg. (360 m i n u s 20) will give t r u t h N o r t h . I t will
t h e r e f o r e be seen t h a t w h e n t h e variation is West it
m u s t be deducted f r o m , and when t h e v a r i a t i o n is.
E a s t it m u s t be added to t h e magnetic bearing in
order to give t h e true bearing. I t will also be seen
t h a t when grid N o r t h is west of true N o r t h the difference m u s t be added to, and w h e n t h e grid N o r t h is
east of t r u e N o r t h the difference m u s t be s u b t r a c t e d
f r o m t h e true b e a r i n g to give t h e grid bearing. If
these rules a r e followed, conversion presents no difficulty, but it is essential to d r a w a r o u g h d i a g r a m t o
prevent errors of sign being introduced.
Scales
T h e r e a r e 63,360 inches to the mile.
Scales on m a p s in the U.K., India, Canada, and'
Australia a r e usually expressed in words showing re10
lations between inches on t h e m a p a n d miles or y a r d s
•on t h e ground—
1
or 1 inch to 1 mile.
63,360
T h e f r a c t i o n in each case is called t h e R e p r e s e n t a tive F r a c t i o n or R.P., and m e a n s one u n i t on t h e m a p
( n u m e r a t o r ) represents a certain n u m b e r of miles on
t h e ground (denominator).
To find t h e n u m b e r of English miles to the inch in
.any m a p t h a t has a n R.F., divide the denominator of
t h e R.F. by 63,360; this gives the n u m b e r of miles to
•the inch.
1
T h u s if t h e R.F. is
15,840
, then
= .25 miles
15,840
63,360
o n t h e ground to one inch on the map.
To find t h e n u m b e r of inches to the mile then, rev e r s e and divide 63,360 by the nominator of t h e R.F.
1
63,360
T h u s if the R.F. is
, then
= 4 inches
15,840
15,840
•to t h e mile.
A scale should be a b o u t six inches long. T h e sizt
d e p e n d s on t h e object f o r which t h e scale is m a d e
R e c o n n a i s s a n c e sketches of an a r e a to explain a plaJi
of a t t a c k or to show lines of advance, of a road or a
river, or of a defensive or outpost position, a r e usua l l y m a d e to t h e scale of 1 to 4 inches to the mile.
Scale to show y a r d s on a map, 4 inches to t h e mils
1
2,000 x. 36
=
. S a y you w a n t 2,000 yards, t h e n
15,840
15,840
= 4.54 inches, length of scale required.
If you w a n t to show y a r d s on a m a p , two inches to
11
1
t h e mile, or
w h e n the n u m b e r of y a r d s is 8,000
31,680
5,000 x 36
then
= 5-68 inches required.
32,680
1
(a) Scale 1 inch to mile
six inches divide into
63,360
six miles and one mile on l e f t of scale into q u a r t e r s ,
or 5.1 inches showing 9,000 y a r d s divided into 1,000
yards.
1
(b) Scale 1 inch to 2 miles
w a n t e d seal®
126,720
f o r body of troops m a r c h i n g t h r e e miles per houv.
Scale of six inches equals 12 miles. Divide i n t o
f o u r sections each equalling t h r e e miles or one hour's
m a r c h . Subdivide l e f t division into twelve p a r t s each
equalling 5 minutes m a r c h .
To construct a scale f o r paces on a map, one over
15,840 (four inches to the mile) six inches would show
I s miles or 2,640 yards. Assuming t h e pace to be
equal to 30 inches, this would equal 3,168 paces, theref o r e you would t a k e 3,000 paces as the length of t h e
scale.
3,000 x 30
= 5.68 inches, length of scale required.
15,840
MAP REFERENCES
The Modified British System
To describe any position or point on a, m a p the.
n u m b e r e d grid lines m u s t be read, first f r o m West to
E a s t and t h e n f r o m South to North, a n d the s q u a r e
in which the point is situated m u s t be m e n t a l l y f u r 12
t h e r sub-divided into t e n t h s on the grid lines in order
t o give a pin point a c c u r a t e reference. T h u s a point
lying between, say West to E a s t grid, 23-24 and South
to N o r t h grid 10 and 11, in the centre of this s q u a r e
would be described by t h e following co-ordinates,
235105.
All points of r e f e r e n c e a r e co-ordinated f r o m t h e
South-West corner of any m a p or square.
The 1 Inch to 1 Mile) and Larger Scale Maps
T h e 10,000 y a r d squares a r e f u r t h e r subdivided into
100 squares of 1,000 y a r d s each side; t h e sides of t h e
10,000 y a r d s q u a r e s a r e thickened and t h e grid lines
a r e numbered. T h e n u m b e r s a p p e a r i n g on a n y grid
line denote, this time in 1,000 y a r d units, t h e distance
of the grid line north or east of t h e point of reference. I n the sheet margin, every grid is so n u m b e r e d
a n d to every tenth n u m b e r is added, in smaller print,
t h e figure required to convert the shortened coo r d i n a t e into the full co-ordinate r e f e r r e d to t h e
(false) origin of t h e grid system. A pin point reference can be given to t h e nearest t e n t h of a 1,000 yards.
Australian Military Maps
T h e A u s t r a l i a n Military Survey is divided into
zones, and a g a i n subdivided into s q u a r e s with a n u m b e r and a letter of t h e alphabet preceding and following t h e n u m b e r — t h u s (1.56H.) 1.56 representing a
l a r g e a r e a of which 1.56H is a 24th part. T h e s e
squares (1.56H) m e a s u r e approximately 100,000 y a r d s
W e s t to E a s t and 120,000 y a r d s South to N o r t h . T h e
lettered s q u a r e is again divided into sections which
a r e n u m b e r e d 1, 2, 3 and 4. E a c h of these sections
m e a s u r e s approximately 50,000 y a r d s West to E a s t ,
a n d 60,000 y a r d s South to N o r t h . E a c h of these n u m bered squares is again divided into two sheets, a N o r t h east, North-west and a South-east, South-west and these
13
a r e each given a name, e.g., "Singleton-Cessnock,"
" B r o k e n Bay-Sydney." T h u s we have a sheet covering, say, "Sydney," which is t h e South-east Southw e s t portion of t h e No. 3 sheet of 156H, a n d this is
t h e size of the m a p issued f o r genera] purposes a n d
its scale is one inch to the mile. This- m a p covers
a n a r e a of g r o u n d 50,000 yards, approximately, W e s t
a n d E a s t , a n d 30,000 yards, South a n d N o r t h .
I t is divided by r e c t a n g u l a r grids, each m a r k e d w i t h
a n u m b e r along the m a r g i n of t h e m a p a n d on t h e
m a p face, every fifth grid w e s t to east is numbered,
a n d every fifth grid south to north is numbered,
a n d every 10th grid r u n n i n g W e s t a n d E a s t a n d
S o u t h a n d N o r t h is m a r k e d in heavy lines. T h e
s q u a r e within these heavy lines shows an a r e a containing 100 squares each 1,000 y a r d s by 1,000 yards.
A t t h e top left-hand corner in the m a r g i n of t h e
m a p is the n a m e of the country, "Australia," a n d t h e
scale, 1:63,360. I n t h e centre is given t h e State
(N.S.W.), a n d u n d e r t h a t t h e name, e.g., "Sydney,"
which shows w h a t p a r t of t h e n u m b e r e d sheet t h e
m a p belongs to. I n t h e right-hand corner will be
found the m a i n reference to t h e m a p as:—
South 156
H III. S.E. & S.W.
T h u s we see we a r e dealing w i t h t h e s o u t h portion of
No. 3 sheet.
P o i n t e r s s h o w i n g grid n o r t h and m a g n e t i c n o r t h
a n d the variation of grid n o r t h and t r u e n o r t h a r e
shown on t h e m a p . On each corner, t h e distances
N o r t h and E a s t , or South and West f r o m t h e point of
grid origin a r e shown, e.g., 450$67 y.E, 830,203 y.N.,
a n d u n d e r n e a t h these t h e b e a r i n g in degrees. O t h e r
figures in blue a n d yellow a r o u n d t h e m a r g i n a r e f o r
14
t
artillery use only. At the bottom of the m a p is given
a c h a r t showing how to give a pin point reference as
explained before. The immediately a d j a c e n t sheets
a r e shown in the m a r g i n and t h e a d j a c e n t sheets
over a wide a r e a a r e given in the index on t h e cover.
The scale shown on the m a p is a six inch scale
divided into six miles, and a 9,000 y a r d scale m e a s u r ing 5.1 inohes, showing divisions of 1,000 y a r d s w i t h
t h e secondaries down to 100 yards. The Vertical
interval of t h e contours is also shown in feet, a n d
along t h e bottom of t h e m a r g i n a r e shown t h e conventional signs used on the map. I n giving a m a p
r e f e r e n c e on this scale, it can be given to within a n
a r e a of 100 yards. F o r example, t a k i n g t h e Sydney
Observatory a s a point f o r reference, the grid m a p
r e f e r e n c e would be Sheet 1.56H I I I S.E. & S.W. or
"Sydney" 207,168.
VISIBILITY
I t is o f t e n of importance to discover f r o m the m a p
whether two points a r e mutually visible. On open
g r o u n d w h e r e t h e r e a r e no trees, hedges, buildings,
etc., one point is visible f r o m a n o t h e r so long as t h e
g r o u n d does n o t rise above t h e line which joins them.
Thus, if t h e country between two points is level,
slopes evenly, is concave, or lower t h a n both of them,
they will be intervisible. But, where a hill or a convex slope intervenes, one point will n o t be visible
f r o m t h e other.
Visibility problems can be a n s w e r e d by inspection
of a contour m a p or sketch in most cases.
But
t h e r e m a y be a doubt. F o r example, a hill between
two points m a y be higher than one of them, but if it
does n o t rise above the line joining t h e m they will
Still be intervisible. A quick method of
finding
w h e t h e r this is so is a s follows:—
To find w h e t h e r two points A and C are intervisible
d r a w a line joining them, a n d on t h a t line note a n y
15
point likely to i n t e r f e r e w i t h t h e line of sight between A a n d C and estimate its height. Suppose
there is a point B t h e height of which is 260 feet, a n d
suppose t h e h e i g h t of A is 300 feet, a n d t h a t of C 200
feet. Measure up on t h e m a p t h e distances A to B
and A to C, suppose A-B is 1,200 y a r d s and A-C is
2,700 yards.
1
T h e slope A-B drops 40 f e e t in 1,200 y a r d s or —.
90
1
The slope A-C drops 100 feet in 2,700 y a r d s or —.
81
This shows t h a t t h e slope A-C is steeper t h a n slope
A-B, a n d t h e r e f o r e B will obstruct t h e view.
A n o t h e r method by simple proportion sum is a s
follows:—
Suppose distance A to D, 700 y a r s d
A to E , 1,520 y a r d s
Difference in height A and D, 50 feet.
Difference in height A a n d E , 75 feet.
The line of sight f r o m A to E rises 75 feet in 1,520
yards. T h e a m o u n t it will rise in 700 y a r d s is f o u n d
by proportion to be 34.5 feet. It t h e r e f o r e passes 15
feet below the s u m m i t of D a n d E will not b e visible
f r o m A.
A n o t h e r method is by d r a w i n g a section.
This
however, requires time, b u t it h a s t h e a d v a n t a g e t h a t
dead g r o u n d is clearly shown.
The extent to which visibility problems c a n be
Solved f r o m t h e map, depends on t h e size of t h e V.I.
If the V.I. is small, t h e u n r e p r e s e n t e d ground f e a t u r e s
a r e small, a n d visibility c a n b e determined w i t h s o m e
accuracy, b u t if t h e V.I. is large t h e reverse is t h e
case. The u n r e p r e s e n t e d g r o u n d f e a t u r e s a r e large.
Visibility t h e r e f o r e should seldom be assumed without inspection of t h e ground.
16
P r o m t h e foregoing t h e following rules c a n b e
formulated:—
i. If t h e m a p or s k e t c h shows two points on t h e opposite sides of a valley standing well above a n y
intervening ground, t h e s e will be intervisible.
ii. I f , between a n y two points, a f e a t u r e is repres e n t e d higher t h a n both, t h e points .will n o t b e
intervisible.
iii. If, b e t w e e n a n y two points, a f e a t u r e is r e p r e sented higher t h a n one of t h e points, t h e points
m a y , or m a y not, be intervisible.
iv. W h e n a slope is shown by t h e m a p to be convex,
two points t h e r e o n will not b e intervisible.
V. W h e n a slope is shown by t h e m a p to be concave,
two points thereon will probably be intervisible.
vi. W h e n ground is s h o w n by t h e m a p t o be level,
the intervisibility of two points will depend entirely upon the absence or presence of such objects as houses or trees.
t
A visibility d i a g r a m showing points visible and invisible f r o m a n observation post c a n be d r a w n . T o
•construct this, identify t h e observation post and a ref e r e n c e object on t h e m a p . D r a w a line b e t w e e n
these a n d m a r k it zero. Set off lines a t 10 degrees
interval r a d i a t i n g on either side of zero line. S t u d y
the features, m a r k on t h e m a p t h e objects a n d f e a t u r e s which i n t e r f e r e w i t h the view f r o m t h e observer's position a n d shade these in. By this m e a n s a
d i a g r a m s h o w i n g no m o r e t h a n grid lines invisible
a r e a s and zero line can be d r a w n which suffice a s a
,guide f o r use on any m a p of t h e s a m e scale a n d
copies can be t a k e n f r o m it.
SECTIONS
Section d r a w i n g is seldom necessary in practice. I t
Is explained because u n d e r certain c i r c u m s t a n c e s it
m a y be a u s e f u l m e t h o d of finding the e x t e n t of d e a d
ground, or of ascertaining w h e t h e r one point is visible f r o m a n o t h e r point.
17
A section h a s been defined as " t h e outline of t h e
intersection of the g r o u n d by a vertical plane"; a.
railway c u t t i n g affords a good illustration of a section. A n o t h e r good illustration is a cottage loaf of
bread cut in half f r o m top to bottom, f o r t h e outline
seen w h e n one-half of the loaf is removed is a fullsized section of t h e loaf. A knowledge of t h e contours a n d of t h e V.I., enables us to d r a w a section of
a hill which will p r e s e n t a f a i r l y a c c u r a t e picture of
t h e slopes as they would a p p e a r if a cutting were
m a d e r i g h t t h r o u g h t h a t hill.
I t is d r a w n as follows:—
On t h e m a p d r a w a n y s t r a i g h t line t h r o u g h the
portion of t h e hill of which a section is required.
M a r k on this line t h e points a t which t h e contours
intersect it. T h e n on a n o t h e r piece of paper, d r a w a.
horizontal line of equal length to represent the level
of t h e lowest contour a n d m a r k on it the contour
intersections. F r o m each of these points d r a w a
p e r p e n d i c u l a r line a n d m a r k on t h e r i g h t and the l e f t
of t h e u p r i g h t s equidistant points representing t h e
V.I. of t h e m a p . T h r o u g h these points draw lines:
parallel to t h e lowest line and m a r k these lines corres p o n d i n g to the heights of t h e contours they represent. T h e n d r a w your section ascending f r o m theb o t t o m to t h e top t h r o u g h t h e points where the perp e n d i c u l a r lines cut the horizontal lines.
SETTING A MAP A N D FINDING A
POSITION ON IT
To set or "orient" a m a p , lay it out to correspond
w i t h t h e g r o u n d directing t h e t r u e n o r t h point on them a p to the north. W h e n this is done it will be seen
tfiat the f e a t u r e s on t h e g r o u n d will be shown in t h e
same direction a s they a r e shown on t h e map. A
m a p can be set by c o m p a s | b y t a k i n g the bearings of'
18
objects both on t h e ground a n d on t h e m a p .
.Setting by Compass
L a y the compass open on t h e m a p a n d t a k i n g a line
t h r o u g h t h e n o t c h in t h e handle, t h r o u g h t h e c e n t r e
axis of t h e compass, along the hair line to t h e n o t c h
in t h e t o n g u e lay this over t h e magnetic n o r t h line
on t h e map. Revolve t h e m a p a n d compass t o g e t h e r
until t h e needle pointing to m a g n e t i c n o r t h is o n t h e
same line a s t h e m a g n e t i c n o r t h line on the m a p .
T h e m a p is now set.
Supposing only t r u e n o r t h is shown on t h e m a p , b y
using a p r o t r a c t o r lay off the magnetic n o r t h f r o m
t h e t r u e n o r t h a n d d r a w ' i n a magnetic n o r t h line,
t h e n c a r r y out the above method.
Setting by Objects
A m a p can be set on t h e ground w i t h o u t t h e use of
a n o r t h point in t h e following m a n n e r : —
(a) If the position of t h e observer can be recognised
•on t h e m a p look f o r some d i s t a n t object on t h e g r o u n d
a n d identify this on t h e map. T h e n join t h e two
points (the position of t h e observer a n d t h e d i s t a n t
object) by a s t r a i g h t line. T u r n t h e m a p until t h i s
line coincides w i t h t h e d i s t a n t object. T h e m a p is
t h e n set.
(b) Supposing t h e position of t h e observer c a n n o t
be a c c u r a t e l y placed on t h e m a p it ' m a y b e possible
b y moving to one side or t h e o t h e r to find some spot
nn prolongation of a fence, row of trees, r a i l w a y line
or s t r e a m or some other f e a t u r e shown on t h e m a p .
I t is possible t h a t a d i s t a n t c h u r c h spire or w a t e r
t o w e r could be identified in a s t r a i g h t line on t h e m a p
w i t h some road corner or f e a t u r e close to t h e observer. If the m a p is placed to coincide with this line,
t h e m a p is set.
(c) T h e simplest way is to identify prominent f e a 19
t u r e s or objects on the m a p which can be seen f r o m
t h e observer's position and hold t h e m a p so t h a t t h e
directions between these objects on t h e ground a n d
t h e m a p a r e parallel.
Finding Position on a Map
F r o m t h e above examples it will be seen t h a t t h e
position of t h e observer is n o t actually fixed, b u t only
a s t r a i g h t line on which it m u s t lie. B u t h a v i n g got
so f a r , t h e m a p now being set, it is quite easy t o
d e t e r m i n e with sufficient a c c u r a c y the position f o r
m a p r e a d i n g t h o u g h not f o r sketching. T h e correct
position can be determined f r o m t h e detail on t h e
m a p . F i r s t of all, get an a p p r o x i m a t e position in r e lation to the general p r o m i n e n t f e a t u r e s such as a
hill, road, river, buildings, etc. Once you have got t h e
general locality you can w o r k out your position exactly b y the smaller objects. F o r instance, you can use
cross roads, a bend in a s t r e a m or river, p r o m i n e n t
building, a bay or a coastline f e a t u r e , and when t h e
m a p is set it is not difficult to find objects t h r o u g h
which a s t r a i g h t line can be produced which will
intersect a n d t h u s determine t h e required position.
Resection
I t m a y h a p p e n occasionally t h a t the country is so
open, or the m a p p e d detail so meagre, t h a t position,
c a n n o t be found f r o m detail n e a r by. I n this case it
is necessary either to move to some spot which can.
be identified, or to employ one or other of t h e m e t h ods of resection b y compass.
The Method of! Enlarging a Map
T h e general idea of enlarging by eye is to copy t h e
detail s h o w n inside a small figure (square, t r i a n g l e ,
etc.) on t h e m a p into a similar b u t l a r g e r figure o n
t h e f r e s h paper.
20
1
T o enlarge a portion of a ma.p, say, of a scale
1
63,360
to a scale
, t h e ratio of increase in t h e size o f
15,840
s q u a r e required f o r this e n l a r g e m e n t is easily found.
63,360
by proportion.
= 4 inches. This m e a n s t h a t a l l
15,840
f o u r sides of t h e square of the original m a p have t o
be increased by this ratio, and to m a k e it easier to
copy in t h e detail, it is advisable to divide the s q u a r e s
on t h e original m a p into still s m a l l e r s q u a r e s and to
divide t h e squares on t h e e n l a r g e m e n t into similar
smaller divisions and copy by eye f r o m one m a p t o
t h e other.
T h e one inch to the mile O r d n a n c e M a p is a scale
useful f o r general purposes, b u t f o r operations in
which very much more detail is required, a scale of
1
(4 ins. to t h e mile), or even l a r g e r is requisite.
15,840.
T H E SERVICE PROTRACTOR
T h e following scales in British u n i t s a r e s h o w n onthe r e c t a n g u l a r service p r o t r a c t o r : —
On t h e F r o n t —
Primaries
Secondaries
1/50,000
1,000 m e t r e s
100 m e t r e s
20 m e t r e s a n d 50
1/25,000
500 m e t r e s
metres
i mile
1/250,000
1 mile
1,000 y a r d s
1/250,000
5,000 y a r d s
100 y a r d s and
200 y a r d s
1/50,000 .. .. .. 1,000 y a r d s
20 yds., 50 yds.
1/25,000
500 y a r d s
a n d 100 yds.
21
O n the
1 inch
1 inch
i inch
1/20,00
1 inch
Back—
to 1 mile
to 1 mile
to 1 mile
to 1 mile
1,000 y a r d s
4,000 y a r d s
1 mile
100 y a r d s
4,000 m e t r e s
1 inch to 1 mile
1,000 m e t r e s
100 y d s ; 25 yds.
1,000 y a r d s
1 mile
20 y a r d s
1,000 m e t r e s
100 m e t r e s ; 250
metres
T h e p r o t r a c t o r h a s degree g r a d u a t i o n s along t h r e e
•edges of the face. The point f r o m which t h e r a y s
a r e d r a w n is m a r k e d by an a r r o w head on t h e f o r e
edge. T h e r e a r e two sets of figures to these gradua t i o n s . T h e outer reads f r o m zero to 180 degrees,
;anid t h e inner f r o m 180 degrees to 360 degrees. All
r e a d i n g s a r e clockwise, m e a s u r e d f r o m north by east,
i T h e angle m a r k e d by a n y g r a d u a t i o n on t h e edge
•of t h e p r o t r a c t o r is m a r k e d toy a line joining t h e
a r r o w h e a d to t h e g r a d u a t i o n in question.
To plot any bearing f r o m any point, lay a prot r a c t o r with t h e zero edge along t h e line r u n n i n g
parallel t h r o u g h this point, with the a r r o w h e a d on t h e
point a n d t h e g r a d u a t e d edge to t h e r i g h t of it.
T h e n any b e a r i n g c a n be m a r k e d off by d r a w i n g a
line t h r o u g h t h e a r r o w point a n d degree shown on
t h e g r a d u a t e d edge. To plot bearings between 180
degrees a n d 360 degrees reverse t h e p r o t r a c t o r a n d
proceed as before. I t is not always necessary to
•draw a line n o r t h a n d south f r o m the point f r o m
"which bearings a r e plotted, because the m e r i d a n or
grid lines on t h e m a p can be used f o r setting t h e
p r o t r a c t o r parallel to n o r t h a n d south.
O n t a k i n g a bearing, it should be noted t h a t t h e
xeverse bea-ring can be r e a d a t t h e s a m e time.
T H E PRISMATIC COMPASS
T h e service prismatic compass of t h e d r y type, Mk.
"VIII, is enclosed in a b r a s s box a n d h a s on the lid a
22
window. T h e r e is a nail clip on t h e box to t h e l e f t
of the handle by which the compass can be opened.
T h e compass is a card beneath a glass cover, a n d
t h e needle is fastened b e n e a t h the card. T h e card is;
of mother-of-pearl, blackened in t h e centre with a n
a r r o w painted with r a d i u m so as to be visible a t night*
T h e needle and its attached card a r e suspended on a
pointed steel pivot which w o r k s on a jewelled boss.
On t h e dial t h e r e a r e two graduations, both increasing w h e n read clockwise, t h e inner figured i n w a r d s
f r o m zero, and t h e outer figured o u t w a r d s f r o m zero.
F a s t e n e d to the inside of the box a t t h e hinge is a n
index w i t h a short vertical line. This is called t h e
lubber line. There is a clamp screw on the r i g h t of
t h e hinge, which, when slackened, enables t h e glass
cover of the box to be rotated, a n d a t t a c h e d to t h e
glass cover n e a r t h e edge is a luminous r a d i u m index
k n o w n as the direction m a r k and corresponding to it,
cutting t h e milling on t h e cover casing, t h e r e is a n
index called a setting vane which m a r k s off 5 degree
g r a d u a t i o n s a r o u n d t h e box. T h e compass c a r d is
motionless being held clear of t h e pivot. I t can be
released b y pushing a stop a w a y f r o m t h e r i n g
handle. This lifts t h e card a n d its boss off t h e steel
pivot so t h a t no d a m a g e is done when t h e boss is n o t
in use, a n d this stop is automatically b r o u g h t intoaction, w h e n t h e lid is closed.
T h e r e is a vertical hairline on t h e window, a t theends of which a r e two luminous strips f o r n i g h t sighting. T h e r e a r e two small holes drilled t h r o u g h these
strips so t h a t if the glass is broken, a horse h a i r o r
t h r e a d c a n be substituted. A tongue extends f r o m
t h e lid. Within t h e ring handle t h e r e is a small'
m a g n i f y i n g prism hinged to a slit in a shield screwed to t h e box. Tilt up t h e casing of this and an eye
hole is revealed above which t h e prism casing is :
23
Blotted. W h e n t h e h a i r line is vertical, the edges of
this sighting slot should be seen as parallel to it.
F o r focussing with t h e magnifier it is necessary to
d r a w u p t h e prism.
•Observing with the Compass
To m a k e a n observation w i t h t h e prism, p u t t h e l e f t
t h u m b t h r o u g h t h e ring and t h e l e f t forefinger u n d e r n e a t h t h e box. T h e r i g h t forefinger should be on t h e
t i n y s t u d which is f o u n d to t h e l e f t of t h e hinge.
T h i s regulates t h e spring which steadies t h e swing
of t h e needle. T h e h a i r line m u s t be vertical. Look
t h r o u g h t h e sighting slot, keep it vertical with t h e
•object to be sighted and, a t t h e same time, r e a d t h e
card. If the h a n d is steady t h e bearing can be read
!to a q u a r t e r of a degree.
F o r use a t night, t u r n t h e glass cover until t h e sett i n g v a n e is over the bearing on t h e outside g r a d u a t i o n of the box, t h e n screw a n d clamp t h e cover a t
this b e a r i n g a n d then direct the axis t o w a r d s t h e
object. I t will t h e n be seen t h a t the direction m a r k
a n d t h e a r r o w h e a d coincide. T h e compass is t h e n
set f o r n i g h t m a r c h i n g on this p a r t i c u l a r bearing.
T o March to this Bearing at Night
T h e direction m a r k and a r r o w h e a d m u s t coincide,
a n d t h e m o v e m e n t m u s t be m a d e in t h e direction of
t h e h a i r line a n d t h e luminous patches on t h e cover.
You will t h e n be m a r c h i n g on t h e b e a r i n g indicated
by t h e setting vane. T h e r u b b e r on t h e bottom of
t h e cover is to p r e v e n t t h e compass f r o m slipping. •
Compass Errors
T h e compass is affected by t h e presence of iro.n,
heavy guns, telegraph wires, b a r b e d wires, d u m p s ,
tractors, iron huts, etc. All t h e s u r f a c e disturbing
elements c a n be avoided, but those u n d e r g r o u n d cann o t be detected except by a n error in t h e compass, b u t
24
when there is this slightest sign of disturbance, if
the compass is shifted, unless there is some wide
magnetic field, this difficulty can be got over. E v e r y
o r d i n a r y compass h a s its individual error a n d theref o r e all compass users should test their compass on.
t r u e bearings such as trigonometry points. Bearings,
c a n be t a k e n also by a circular p r o t r a c t o r on a l a r g e
scale map.
Night Marching
N i g h t m a r c h i n g requires long practice and care. A
slight knowledge of elementary a s t r o n o m y is useful.
T h e line of luminous patches in t h e lid fully extended will indicate t h e line of advance, b u t it is always^
wise to try and pick u p f r o m the compass b e a r i n g
some point or object which can be seen in t h e d a r k
to m a r c h on. W h e n no object or s t a r is available a3
guide, a white p a t c h sewn on t h e b a c k of a guide who«
will be s e n t f o r w a r d by stages and halted when indistinguishable will simplify the correct m o v e m e n t on a
bearing.
RECONNAISSANCE REPORT
T h e value of a r e p o r t is enhanced if accompanied
by a map, sketch, drawing or photograph. B u t these
m u s t only be used to m a k e t h e subject m a t t e r clearer to t h e r e a d e r a n d to decrease t h e w r i t t e n word.
Before proceeding on a reconnaissance t h e best
available m a p m u s t be procured a n d in one's ownt e r r i t o r y all topographical information should be
g a t h e r e d f r o m local council administrative maps, etc.
A r e p o r t should include details of t h e n a t u r e of all
f e a t u r e s which m a y affect operations, movements,
supplies. Included in it should be seasonal weather 1
effects, such as floods or droughts, and p a r t i c u l a r a t tention paid to the classification of all roads. From,
a geological point of view t h e n a t u r e of t h e soil and'
its conditions in wet periods, rocks and b r o k e n coun25
t r y which would m a k e it difficult f o r aeroplane landing, places w h e r e w a t e r m a y be h a d by boring, deposits of stone or metal f o r road mending. Most of
this i n f o r m a t i o n c a n be p r o c u r e d f r o m t h e local inh a b i t a n t s in advance. Maps a r e never p e r f e c t even
Where t h e r e a r e large scale m a p s a great deal of detail h a s to be added to bring t h e m "up-to-date a n d to
m a k e t h e m of any value f r o m a military point of
view. Do not hesitate to m a k e a n e n l a r g e m e n t of a
.given area, a d d i n g to it a n y detail or i n f o r m a t i o n
relevant to t h e r e p o r t to be prepared.
Drawings and Sketching
A p a n o r a m a d r a w n f r o m a n observation post is of
•great value. I t need not be an artistic drawing, b u t
practice is necessary to obtain clarity. T h e following
rules will aid:—
i. A considerable portion of time should be spent
by studying t h e g r o u n d by eye a n d field glasses.
ii. The perspective m u s t be t a k e n into account.
Objects f a r a w a y a p p e a r to be smaller, and m u s t be
so represented on the drawing. Roads, railway lines,
r e p r e s e n t e d by parallel lines a p p e a r to m e e t a t a
v a n i s h i n g point on the horizon.
iii. All buildings, trees, n a t u r a l f e a t u r e s should be
d r a w n in outline only in order to convey t h e impression of shape. A n y wooded a r e a s m a y be slightly
•"hatched."
iv. Simplicity is t h e basis of a d r a w i n g a n d firm
continuous lines m u s t be used throughout.
Before commencing a drawing, decide how m u c h is
to be included. Military p a n o r a m a s are, as a rule,
iimited to a 30 degrees of arc. If the service prot r a c t o r is held horizontally eleven inches f r o m t h e
eye, it covers a n angle of approximately 25 degrees.
26
Framework
D r a w a m e a n horizontal line along the horizon a n d
t h r o u g h t h e centre d r a w a vertical line f r o m t h e obs e r v e r as t h e central axis of sight. F i x all outstanding points and p r o m i n e n t objects in their correct
positions. By using the p r o t r a c t o r a n d t h e g r a d u a t e d
edges, it can be observed w h a t g r a d u a t i o n coincides
"with t h e object to be d r a w n a n d the position of t h e s e
c a n be m a r k e d on t h e p a p e r by laying t h e p r o t r a c t o r .
o n the d r a w i n g and m a r k i n g t h e m off. Vertical dist a n c e s can he obtained by using the p r o t r a c t o r with
t h e long side vertical. T h u s any point can be accurately plotted on t h e drawing. W h e n this is done,
o t h e r detail can be fitted in by eye or f u r t h e r m e a s u r e m e n t . Sketch the whole in, lightly a t first, t h e n
t h o r o u g h l y examine t h e sketch and compare it w i t h
t h e a r e a it represents seeing t h a t no detail is omitted,
t h e n complete the sketch by d r a w i n g in with f u r t h e r
lines, t h i c k in t h e f o r e g r o u n d and t h i n n e r as t h e y
recede into the distance. All o u t s t a n d i n g p o i n t s
should be m a r k e d by a vertical line r u n n i n g to t h e
top of t h e drawing, their m a p location given, t h e i r
description a n d their b e a r i n g w r i t t e n in block letters
a t t h e top of t h e vertical line. W h e n the d r a w i n g is
complete, the following information m u s t be added,
in addition to above:—
ii T h e position of t h e observation post by m a p reference, the bearing of the centre of the sketch f r o m
t h e observation post.
ii. T h e name, r a n k , and regiment of t h e observer.
iii. T h e date, the time and the w e a t h e r conditions.
iv. Any indication of our own or enemy troops in
t h e usual conventional sign, blue or red.
Small Sketches
Small sketches can be used to illustrate
27
details.
:such as bridges, fords, -watering points, road detours,
etc. W h e r e t h e r e a r e difficult t u r n s t h r o u g h built-up
areas, a small sketch with m a p reference a n d description showing a n a r r o w h e a d f o r c h a n g e of direction -will be of g r e a t value. These little s k e t c h e s m u s t
be p r e p a r e d in t h e s a m e w a y a s the p a n o r a m a — m a i n
details first a n d in correct position distance.
'Reads
Most i n f o r m a t i o n required a b o u t roads c a n be
shown on a m a p a n d r o a d s should be classifid w i t h
r e g a r d to width, s u r f a c e a n d foundation. An A Class
road, wide enough to take two s t r e a m s of traffic.
B Class road wide enough to t a k e one s t r e a m of
traffic with a n occasional vehicle passing in t h e
s t r e a m . C Class road only wide enough f o r one
s t r e a m of traffic.
These A, B a n d C Class r o a d s should a g a i n be
•divided into different categories.
A No. 1 r o a d capable of t a k i n g three ton lorries,
heavy guns, etc.
No. 2 road capable of t a k i n g light c a r s a n d one
t o n lorries.
No. 3 r o a d fit only f o r horse t r a n s p o r t .
No. i notfit f o r any vehicles.
T h u s we h a v e a road described as A 1, 2, 3 or 4, etc.
The s u r f a c e of a road deteriorates in wet w e a t h e r ,
t h e r e f o r e classify this. Also mention t h e type of
metalling employed a n d w h a t w e a r i n g it will stand
up to, also mention w h e r e the nearest supply of road
metal f o r m e n d i n g purposes is available.
Military Bridges
i. L i g h t Bridges (a) Foot Bridges, Inf. in single file;
(b) P a c k bridges, Inf. in file p a c k
animals, etc.
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ii. Medium
Bridge. Inf. in column, m o t o r cars,
a r m o u r e d ears, light and medium artillery, 3-ton lorries a n d
all M.T. u p to 5i t o n s axle
load, also t r a c k vehicles to 8
tons, t r a c k not to exceed 8
foot 9 inches.
iii. H e a v y Bridges. Heavy artillery, t r a c t o r s , M.T.
to 16 tons axle load t a n k s up
to 18 tons.
iv. Superheavy Bridges. Axle loads a n d t a n k s in
excess of above.
A g u a r d should be posted to control traffic a n d
c h e c k unauthorised weights. Notices should be posted
Showing traffic allowed. Traffic over bridge generally
slow.
Fords
• The following a r e the f o r d a b l e depths:—
Cavalry—4 feet.
Infantry—3 feet.
T a n k s — i feet.
Light Artillery—2 feet 6 inches.
Dragons—2 feet 6 inches.
Lorries—2 feet.
Motor Cars—1 foot 6 inches.
Motor cycles—1 foot.
Good bottoms a r e essential f o r heavy traffic. Sandy
bottoms get stirred u p and depth increases.
In
the straight p a r t of a river the depth is u n i f o r m ,
generally g r e a t e r a t a concave b a n k a n d less a t a
convex b a n k and when a river is not f o r d a b l e
straight across, a passable slanting course c a n o f t e n
be found between two bends.
All fords should be clearly m a r k e d , pickets should
be driven in above and below a ford, their h e a d s con29
nected by s t r o n g rope a n d t h e m a r k s on the pickets,
should show t h r e e and f o u r f e e t above t h e bottom,
to m a r k t h e rise of t h e w a t e r .
T h e velocity of a r i v e r can be f o u n d by t h r o w i n g
a piece of wood well o u t into t h e s t r e a m and m e a s u r ing—and t i m i n g it over a given n u m b e r of feet. Them e a n velocity equals 4-5ths of t h e s u r f a c e velocity,,
a n d 7/8ths of t h e m e a n velocity in f e e t per second
equals t h e n u m b e r of miles per hour.
T o get t h e yield of a s t r e a m select some 15 y a r d s
of f a i r l y u n i f o r m channel, t a k e t h e b r e a d t h a n d avera g e d e p t h in f e e t a t several places, get t h e s u r f a c e
velocity a s s h o w n above, t h e n multiply t h e m e a n
velocity b y sectional a r e a , this will give yield p e r
second in cubic feet.
O n e cubic foot equals six a n d a q u a r t e r gallons a n d
one gallon weighs 10 lbs.
Daily a v e r a g e m a n , d r i n k i n g a n d cooking 1 gallon.
I n a s t a n d i n g camp, average f o r m a n 5 gallons,
f o r horse or camel 10 gallons. :
RANGE CARDS
Attack
i. K a n g e s to be t a k e n in direct line of advance.
ii. D r a w parallel lines a n d fill in s t a r t i n g point a n d
objective.
iii. T a k e r a n g e t o objective a n d w r i t e in right-hand
column, select some object half-way t o objective
a n d enter r a n g e in right-hand column.
iv. Select and t a k e r a n g e s to other intermediate
objects, those easily recognised w h e n reached
a n d w h i c h a p p e a r t o b e n e a r probable fire positions. •
30
v. Simple subtraction will give you r a n g e f o r each
successive object to objective. E n t e r these in
left-.hand column and strike o u t right-hand
column.
Yards
0
100
700
900
1,300
1,700
Yards
1,700
Small wood 1,600
Ruined F a r m
1,000
Mound with bush
800
Line of poplars
400
S t a r t i n g point (described)
0
Objective (described)
Defence
i. M a r k off on card positions f r o m which r a n g e is
taken.
ii. Describe position accurately. .
ill. Select a n unmistakable object a n d d r a w a
thick setting ray to it.
iv. D r a w these semi-cifcles representing 600, 1,000,
1,500 yards respectively. This caii be conveniently d r a w n with a circular p r o t r a c t o r .
vi. Select objects to r a n g e on, e.g., positions which
enemy may occupy or have to pass, obstacles,
bridges, gaps in fences, etc.
•vi. Keeping card on setting ray, d r a w r a y s to
show direction of objects and of lengths corresponding to distances.
vii. W r i t e s h o r t description of each object
in
block lettering or d r a w signs.
viii. W r i t e distance to each object against description.
N.B.: Avoid drawing too m a n y r a y s which a r e
a p t to confuse and where possible, m a k e one
r a y do f o r more t h a n one object.
31
Wholly set up and printed in Australia, by IUawarra Newspapers Pty.
Ltd., Wollongong.
1942