OBSERVATION OF FIRE.
The observation of fire is essentially the following operation,
repeated for each shot or salvo: Locating on the ground the position of
one point, which is the point of burst, and announcing its situation
in reference to another point, which is the target.
But it has been demonstrated that it is impossible, without using the
map, to determine the error in range of one point relatively to another
point not on the same alignment.
The operation must consist in:
1. Spotting on the map the point of burst.
2. Reading its position in reference to the target.
The observation of the burst--that is, the spotting of the point of
impact--is the same whether the observation is direct or lateral.
1. PREPARATION OF THE FIRE.
=Draw on the map, and copy if possible on a vertical photograph, the
line balloon target (alignment of the center of the objective) and
draw through this point a perpendicular to the alignment. In case the
observation is lateral, draw also the line battery target and its
perpendicular.=
To draw the line balloon target, it is not necessary to know the
horizontal projection of the balloon. It is enough to find on the
ground a point situated directly on the alignment of the center of the
objective.
2. OBSERVATION OF A SHOT.
=When the shell bursts, take quickly an alignment and reference points
in range of the point of burst; spot this point on the map or on the
photograph; give its error in reference to the line battery-target,
measuring it by the scale on the map or on the photograph.= (It is
well to put the graphic scale on the photos.)
The delicate part of the operation consists in seeing the shot at the
moment of burst. One must try to spot the apex of the inverted cone
formed by the burst, without paying any attention to the more or less
considerable cloud of smoke which follows and which will cause mistakes
if the burst was not seen immediately. The method of situating the
point is the same as that described above.
For the direction, one reference point is enough, because one can
consider the alignment of the point as practically parallel to the
balloon-target. For the range, a rapid study of the terrain before the
fire is sufficient to allow the observer to know the reference points
by which he can guide himself. His eyes must never leave the point of
burst until he has fixed well in his mind its situation in reference to
appropriate reference points. Not to do this would lead to errors and
to loss of time while he has to find the point again with his glasses
to study it some more.
When the observation is direct, the direction of the burst is,
of course, known as soon as it is seen. When the observation is
lateral, it is well to remember that the line battery-target can not
be materialized on the ground because it is in reality an _oblique
alignment_, leading to the same errors which we have discussed. It
follows all irregularities of the ground and, on account of this, can
not be followed exactly in oblique vision.
Particularly around batteries, the ground is often very irregular.
There may even be little spaces of dead ground, caused by hollows which
the map does not always show. The above method, applied with the help
of photographs, allows you to avoid errors resulting from the existence
of these hidden parts.
PRACTICAL ADVICE.
1. _Work sitting down, with the map on your knees and leaning against
the edge of the basket._
This position is preferable to all others, because it allows the
observer--
(_a_) To correct with his head and shoulders the movements of the
basket.
(_b_) To have the map always before him. He can consult it at any
moment, mark the necessary alignments without loss of time, use it as a
desk for drawing or taking notes, or as a wind shield when looking at
photographs.
The observer who works standing up must either pick up his map from
the bottom of the basket every time he needs it, which is out of
the question, or fasten it outside the basket; the latter solution
is inadvisable, it necessitates working in the wind when the map is
referred to, and every time the observer turns to look at his map he
disturbs the equilibrium of the basket.
It is advisable to work standing up only on days when there is
practically no wind, and the balloon is continually turning and never
becomes oriented.
2. _Have always within reach a flat rule, a pencil, and a duodecimeter
rule._
To be able to trace an alignment on the map with precision, the rule
must rest on a firm surface. This happens when the map is mounted on a
drawing board; when it is mounted on a frame with rollers, the frame
should have, between the two thicknesses of the map, a board level
with the edges of the frame on which the rule can slide with its whole
length on the map.
With a hard pencil, well sharpened, precise and neat alignments can be
drawn.
The duodecimeter rule is for measuring distances on photographs and on
the map; chiefly in observations of fire.
3. _Hold the field glasses with both hands._
This advice, sometimes ignored by observers without expedience, has a
great influence on the accuracy of information. When an observer holds
the glasses in one hand, it is much more difficult for him to correct
the movements caused by the balloon and to concentrate on a point. It
is very important, therefore, to hold the glasses firmly with both
hands, especially when you are making a delicate observation or when
you wish to study an “objective” in detail.
PART III.
APPENDIX.
NOTE 1.--All observations of rounds refer to the line battery target
(_b-t_) and a line perpendicular to same passing through the target.
Observations are given in meters right and left and whether the round
is over or short. Indications as to deflection are given before those
of range. Indications as to the amount of error precede those as to the
sense of the error. Example, 50 meters “Right,” “over.” Owing to the
dispersion of fire when adjusting fire for field artillery or howitzer,
it is unnecessary and of little value to the battery to give the amount
of the error in range except when asked for by the battery commander or
when the error in range is abnormal (over 200 meters).
When the target is clearly visible and the effect of a round hitting
a target is evident, the observation “Target” is reported. Unless
the observer is certain of having seen the bursts “Unobserved” will
be sent. If, however, after a few seconds smoke can be seen rising
from trees, houses, etc., in proximity to the target, the observation
“Unobserved, but smoke seen rising left and over,” may be given.
NOTE 2.--Observers must beware of being over-confident in their own
powers of observation. True confidence only comes with experience, and
this is best attained by making ascents with a trained observer when
ranging a battery and checking one’s own observations with those given
by him. An observation must never be given unless the observer is quite
certain as to its correctness. It is essential to good results that
the artillery may be able to rely absolutely on the observations sent
down. The observer must watch the target but must avoid straining his
eyes by putting up his glasses as soon as a round is fired. He should
arrange for the chart room to inform him when a shell is about to
fall. The latter must know the time of flight. Observers must learn to
distinguish readily the bursts of different kinds of shells.
NOTE 3.--If the balloon-target line makes an angle with the
battery-target line of more than 30° with field artillery and 20° with
heavy, the balloon position will be given to the battery, and all
observations will be given with reference to the balloon-target line
and the battery will replot accordingly.