TM 5-6675-250-10
2-11. GENERAL
The SIAGL is required to operate in all climatic conditions; however, due to known design limitations of
theodolites, the following procedures must be used to permit successful operation.
a.
Avoid subjecting the instrument to extreme sudden changes in temperature.
Allow the instrument to stabilize at the operating temperature.
b.
Select operating sites that can shield or protect the instrument from the full effects of extreme
c.
environment. Make use of any available tents or other shelters.
At the completion of a mission return the instrument to the sheltered site to prevent its needless
d.
exposure to harsh environments.
e.
Remove moisture and fogging of the optics by placing the instrument in a warm, dry place (locally
fabricated "hot box") and using a desiccant.
f.
Adhere to "local regions" standard operation, maintenance, and storage procedures.
Ensure that the equipment is clean and dry prior to replacing.
g.
2-12. OPERATING IN EXTREME COLD - BELOW 0F. (-17.78C)
With proper precautions, servicing, and theodolite lubrication, the SIAGL can be used in extreme cold. Its
use is limited only by the endurance of operating personnel and conditions affecting visibility. The instru-
ment should be kept out-of-doors or in unheated buildings for short periods of non-use. For temperature
below 0F(-17.78C), allow 20 minutes for warmup. Warmup can be accomplished by following the nor-
mal operating procedures but ignoring the first READ AZIMUTH indication. Operate the theodolite con-
trols slowly and evenly to avoid stressing mechanical parts. Do not attempt to straighten or unnecessarily
bend the cables. At temperatures below -40F(-40C), turn the GRU both clockwise and counter-
clockwise about the intended azimuth reading before initiating a gyro compass observation.
2-13. OPERATION IN EXTREME HEAT
The SIAGL is designed to operate in extreme heat up to 125F (51.6C); however, to avoid degradation of
accuracy due to internal theodolite distortion, the instrument should be protected from direct sunlight by
an umbrella or other suitable shelter.
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