TM 5-6675-250-10
2-8. OPERATION OF AUXILIARY EQUIPMENT - Continued
PLUMB BOB ASSEMBLY
The plumb bob assembly is used with the auxil-
iary tripod assembly to plumb the GRU. To use,
the plumb bob extension hook (1) is threaded
through the bridge screw and attached to the
pointer (2) on the underside of the GRU housing
(3).
RAIN AND DUST COVER
A rain and dust cover is provided to protect the
t h e o d o l i t e when operating under adverse
weather conditions. Remove the rain and dust
cover (1) from the transit case and place over
the theodolite when operating where the equip-
ment is exposed to dust or moisture. Remove
the cover (1) as needed to take theodolite read-
ings; keep the cover over the theodolite when it
does not interfere with operations.
WIND SHELTER
The SIAGL is designed to perform accur-
a.
ately in winds up to 20 mph (32 kmph).
Wind disturbances can be detected by a
difficulty in obtaining a steady BIAS null
and extended observation times. In winds
in excess of 20 mph (32 kmph), it is recom-
mended that the wind shelter be used to
protect the equipment and maintain an
accuracy to performance.
To set up the wind shelter, erect lower
b.
panel assembly (1) by positioning edge of
panel between metal brace and flap, and
secure with snap fasteners (6). Place
assembly over erected instrument and
position to prevent any contact with the
instrument during operation. Pin the skirts
(2) of the lower panel assembly firmly to
the ground with pins (3). Assemble the
upper panel assembly (4); stretch cover (5)
over upper panel and secure with snap
f a s t e n e r s (6). When the instrument is
uncaged in the BIAS or GC mode, press
upper panel assembly firmly onto lower
panel assembly. Remove the upper panel
assembly to read azimuth. When operating
in areas of sand or loamy soils, place rock
and sod over the lower panel skirts and
pins to provide maximum stability of the
shelter.
2-55
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