TM 5-6675-306-14
Section V. OPERATION UNDER UNUSUAL CONDITIONS
2-14. Operation under Rainy or Humid Conditions
2-11. Operation in Extreme Cold (Below 0F.) (-
18C.)
In humid areas, a slight lowering of the temperature will
cause condensation of moisture and fogging of lenses
With proper precautions and servicing, the theodolite
and prisms. Internal fogging can usually be removed by
can be used in extreme cold. Its use is limited only by
placing the theodolite in a warm, dry place. Corrosion
the endurance of operating personnel and conditions
caused by high humidity can be partially eliminated by
affecting visibility. The theodolite should be kept out-of-
using warm, dry storage areas and desiccants. After
doors or in unheated buildings for short periods of
use, dry the instrument thoroughly with a soft, lint-free
nonuse. Extreme temperature changes will induce
cloth.
internal stresses affecting accuracy and lenses, and
2-15. Operation in Salt Water Areas
prisms may become fogged. Theodolites to be used
When operating the theodolite in salt water areas, wipe
under conditions of extreme cold should be cleaned,
the instrument frequently with a soft, clean cloth. If the
and all lubricants should be removed before the
theodolite is exposed to direct salt spray, it should be
instruments are used.
CAUTION
cleaned thoroughly and should be returned to an
instrument shop for overhauling as soon as possible.
Avoid subjecting the theodolite to
Cleaning intervals should be shortened considerably for
sudden changes in temperature.
2-12. Operation in Extreme Heat
theodolites subjected to salt air exposure. Salt is highly
corrosive to metal.
Operation of the theodolite in extreme heat and under
2-16. Operation in Snow
the direct rays of the sun can cause internal stresses
Visibility is sharply reduced while snow is falling. When
and distortion in the instrument and produce poor
taking sightings after a snowfall, the use of suitable dark
sightings because of heat waves. If possible, the
glasses by the instrument man will reduce eyestrain and
theodolite and the instrument man should be protected
fatigue. If snow conditions are accompanied by extreme
from the direct sunlight by an umbrella or other suitable
cold (below 0 F.) (-18'C.), refer to paragraph 2-11.
means. Under these conditions, shorter sightings will
2-17. Operation in Mud
decrease the amount of sighting errors.
Taking
Mud is highly abrasive and if allowed to remain on
sightings during early morning and late evening will also
threaded or sliding surfaces, moving parts of the
minimize error magnitude. The use of suitable dark
theodolite will soon bind and the instrument will become
glasses by the instrument man will reduce eyestrain and
inaccurate or inoperable. The theodolite should be
fatigue. If the theodolite is kept in a cool storage place,
carefully wiped clean. Be extremely careful not to
it should be removed from storage in sufficient time
scratch lens and prism surfaces during cleaning
before use to allow the temperature of the metal to
operations. Place a protective cover over the theodolite
approach that of the outside air.
2-13. Operation in Dusty or Sandy Areas
when not in use. When the tripod is set up on muddy
ground, leveling is extremely important and should be
Special care must be given instruments which are being
checked frequently. Anchor tripod legs firmly to avoid
used in dusty or sandy areas, since both dust and sand
slippage which will cause incorrect readings.
are highly abrasive. If dust and sand are allowed to
2-18. Operation at High Altitudes
remain on threaded or sliding surfaces, moving parts of
No special procedures are required to operate the
the theodolite will soon bind and the instrument will
theodolite at high altitudes.
become inaccurate or inoperable. The theodolite should
be brushed frequently and carefully wiped clean. Be
extremely careful not to scratch lens and prism surfaces
during cleaning operations.
Always protect the
instrument from blowing dust and sand. Place a
protective cover over the theodolite when it is not in use.
2-36
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