TM 5-6675-312-14
equipment and the operator should be protected from the direct sunlight by an umbrella or other suitable means. Under
these conditions, shorter sightings will decrease the amount of sighting errors. Taking sightings during early morning and
late evening will also minimize error magnitude. The use of suitable dark glasses by the operator will reduce eyestrain
and fatigue. If the equipment is kept in cool storage place, it should be removed from storage in sufficient time before
use to allow the temperature of the metal to approach that of the outside air.
c. Operation in Dusty or Sandy Areas. Special care must be given equipment which is being used in dusty or sandy
areas, since both dust and sand are highly abrasive. If dust and sand are allowed to remain on threaded or sliding
surfaces, moving parts of the equipment will soon bind and the equipment will become inaccurate or inoperable. The
equipment should be brushed frequently with the dust brush and carefully wiped clean with a soft lint-free cloth. Be
extremely careful not to scratch lens and prism surfaces during cleaning operations. Always protect the equipment from
blowing dust and sand. Place the dust/rain cover over the theodolite when it is not in use.
d. Operation Under Rainy or Humid Conditions. In humid areas, a slight lowering of the temperature will cause
condensation of moisture and fogging of lenses and prisms. Internal fogging can usually be removed by placing the
equipment in a warm, dry place. Corrosion caused by high humidity can be partially eliminated by using warm, dry
storage areas and desiccants. After use, dry the equipment thoroughly with a soft, lint-free cloth. Place the dust/rain
cover over the theodolite when it is not in use.
e. Operation in Salt Water Areas. When operating the equipment in salt water areas, wipe the instrument
frequently with a soft lint-free cloth. If the equipment is exposed to direct salt spray, it should be cleaned thoroughly and
should be
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