TM 5-6675-302-14&P
Section V. OPERATION UNDER UNUSUAL CONDITIONS
equipment off frequently and carefully wipe it
clean. Always protect the equipment from dust or
sand that is blowing where the equipment is not in
use.
2-16. Operation Under Rainy or Humid Condi-
2-13. Operation in Extreme Cold (below 0°
F). With proper precautions, the target set can be
used in extreme cold. Its use is limited by the en-
durance of operating personnel and by the condi-
tions affecting visibility. The target set should be
kept out-of-doors or in unheated building for short
periods of non-use. Extreme changes in
temperature will cause stresses affecting accuracy.
The target should be cleaned and all possible
lubricants removed before being put to use under
extreme cold. Snowfall, winds, and refraction of
light are some of the adverse conditions en-
countered at low temperatures.
2-14. Operation in Extreme Heat. The target set
should be protected by a surveyor’s umbrella dur-
ing strong sunlight. Direct rays of the sun will
cause stresses and distortion in the equipment.
Heat ripples in the air near the ground level create
poor sighting conditions. When such conditions
prevail, taking shorter sightings will reduce
sighting errors. If the target set is kept in a cool
storage place, it should be brought out of storage
before use to let the equipment temperature ap
proach that of the outside air.
2-15. Operation in Dusty or Sandy Areas. Special
care must be taken of an instrument that is being
used in areas where dust and sand occur, since
both dust and sand are highly abrasive. Moving
parts will soon bind if they are allowed to remain
on threaded or sliding surfaces, and the equipment
will become inaccurate or inoperable. Brush the
2-14
tions. In humid areas, a slight lowering of the am-
bient temperature can cause condensation of
moisture and fogging of the target lens. Internal
fogging of the lens can usually be removed by tak-
ing the equipment into a warm, dry place. Corro-
sion due to high humidity can be kept to a
minimum by using warm, dry storage areas, and
by the use of desiccants. Dry the equipment
thoroughly after use and wipe all metal parts with
a soft cloth lightly impregnated with watch oil. Do
not get any of the oil on the lens or level vial sur-
faces.
2-17. Operation in Salt Water Areas. Salt air is
highly corrosive to metals and especially to brass,
from which many parts are made. Salt reacts with
brass to produce a green deposit (verdigris), which
must be guarded against and removed as soon as it
is noticed. Wipe the equipment frequently with a
soft cloth and dry thoroughly. Clean the equip
ment daily and apply a light film of watch oil to
metal parts.
2-18. Operation at High Altitudes. No special
operating procedures are required at high
altitudes.
