september - october - Fort Sill

THE FIELD ARTILLERY JOURNAL
COMPASS METHOD
In many cases it will be found that no suitable reference points can be
identified. In actual practice this case has arisen so frequently and the
compass method has given such unvarying success that many officers have
come to the conclusion that the compass method should be employed as the
normal procedure in the identification of targets.
The principle employed is the parallel method with the added advantage
over the reference point method of having only one offset to compute, viz.,
the offset on the target. (Magnetic north is considered at an infinite
distance.)
The battalion commander sends to his battery commanders a
compass bearing corrected for their displacement. He also sends the site
of the target, the range, and a description of the locality. Good results
have been obtained with a hand prismatic compass of the type which
was part of the equipment in 1917 (Keuffel and Esser). The aiming
circle, however, is much superior and is sufficiently portable to be
carried by the parties of the battalion and battery commanders on their
initial reconnaissances.
The following detailed procedure usually obtains good results.
All stations set the scales of their aiming circles at zero, release the
needle, and centre the needle by means of the lower motion. When the
needle is at rest and centred, the line of sight of the aiming circle is
pointing to magnetic north and the bearing to any target may be easily read
by merely turning the upper scale of the instrument on the target whose
bearing is desired.
Just at this point the battery commander's telescope may be used to
great advantage. Its zero should be placed on magnetic north and then it
will read magnetic bearings. This may be accomplished by using the
aiming circle to select a distant point which is in line with magnetic
north.
The battery commander who receives a bearing from the battalion
commander (corrected for displacement) only has to turn his telescope to
the reading received and he should find the target within his field of view.
If the declination constants of the various aiming circles within the
battalion vary considerably, a correction for these variations must be made.
If Y azimuths are used this correction is unnecessary. For this reason
the Y azimuth method is recommended.
A nice refinement to this method may be made by designating
several points at various ranges in the normal zone of the battalion and
requiring the batteries to give their actual readings on same. The
difference in these readings from those taken at the battalion
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