The magnetic compass is the most commonly
used and simplest instrument for measuring
directions and angles in the field. This instrument
has a variety of both civilian and military
applications. The LENSATIC COMPASS (available in
your Table of Allowance) is most commonly used for
SEABEE compass courses, for map orientation, and
for angle direction during mortar and field artillery
fires.
In addition to this type of compass, there are
several others used exclusively for field surveys. The
ENGINEER’S TRANSIT COMPASS, located between
the standards on the upper plate, is graduated from
0° through 360° for measuring azimuths, and in
quadrants of 90° for measuring bearings (fig. 11-4).
Notice in figure 11-4 that the east and west markings
are reversed. This permits direct reading of the
magnetic direction.
The compass shown in figure 11-5 is commonly
called the BRUNTON POCKET TRANSIT. This
instrument is a combination compass and clinometer.
It can be mounted on a light tripod or staff, or it may
be cradled in the palm of the hand.
Other types of compasses can also be found in
some surveying instruments, such as the theodolite
and plane table.
Figure 11-4.-Engineer’s transit compass.
ENGINEER’S TRANSIT
A primary survey fieldwork consists of
measuring horizontal and vertical angles or
directions and extending straight lines. The
instruments that can perform these functions have
additional refinements (built-in) that can be used for
other survey operations, such as leveling. Two types
of instruments that fall into this category are the
engineer’s transit and the theodolite. In recent years,
manufacturing improvements have permitted con-
struction of direct-reading theodolites that are soon to
replace the vernier-reading transits. However, in
most SEABEE construction, the engineer’s transit is
still the major surveying instrument.
45.742
Figure 11-5.-A Brunton pocket transit.
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