TM 5-6675-307-14
(c) Transit telescope on its elevation axis,
recheck centering of the altitude level bubble, and point
on same target. Record the elevation angle.
(d) The sum of the angles obtained in steps (b)
and (c) above should equal 360 + 0.4 minute.
(e) If deviation is more than 0.4 minute,
perform adjustment given in paragraph (2) below.
(2) Adjustment.
Refer to figure 2-21 and adjust
vertical circle index.
Figure 2-18. Vertical circle index, adjustment
Section V. OPERATION UNDER UNUSUAL CONDITIONS
2-10. Operation in Extreme Cold (Below 0 F.) The
and distortion may occur which would result in poor
sightings. If possible, the theodolite should be protected
theodolite and its accessories may be used in extreme
from the sun by a surveyor's field umbrella or other
cold with no adverse effect on its capabilities. Its use is
suitable means. Taking sightings during early morning
limited only by the endurance of the operating personnel
or late evening will help to minimize error magnitude.
and conditions affecting visibility.
CAUTION
Also, shorter sightings will decrease the amount of
sighting error.
Avoid subjecting the instrument to
sudden
changes
in
temperature.
NOTE
Extreme temperature changes may
If the theodolite is kept in a cool storage
cause
internal
stresses
affecting
area, it should be removed from storage
accuracy and optical components may
in sufficient time before use to allow the
become fogged.
WARNING
temperature of the instrument to
During operation in subfreezing
approach that of the outside air.
temperatures, avoid touching any
2-12. Operation in Dusty or Sandy Areas
portion of the instrument with bare
Special precautions must be observed when the
hands except the controls. Bare skin
theodolite is used in a dusty or sandy environment, as
will stick to extremely cold metal parts.
dust and sand are highly abrasive. If foreign matter
adheres to mating surfaces, the mechanisms may bind.
2-11. Operation in Extreme Heat
The instrument should be frequently brushed and wiped
If the theodolite is operated in extreme heat and under
clean. Optical surfaces should be brushed with the
the direct rays of the sun, internal stresses
brush in the
2-19
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