ARMY TM 9-6675-349-12&P
MARINE CORPS TM 11039A-12&P
3-38. Operation at Extreme Northern or Southern Latitudes.
The IPADS initialization procedure requires a two-step approach to assure that accuracies are met at latitudes
greater than 65. Normal and hot start initialization times increase to 20 and 10 minutes, respectively. Half way
through initialization, the CDU will prompt the operator audibly and visually to turn the vehicle around,
approximately 180. The CDU also displays driver guidance instructions, for turning the vehicle, until the
correct heading is reached. The IPADS will then continue to initialize and alert the operator when ready to start
surveying.
IPADS horizontal position accuracy degrades at higher latitudes. When the operational situation permits, use
the following techniques to plan survey missions and keep horizontal position errors within allowable limits:
NOTE
At high latitudes, azimuth misalignment is a major contributor to IPADS
horizontal position error. Adjustment doesn't remove azimuth misalignment
error when the survey is closed back at the starting point.
a.
Close the survey at a known SCP other than the starting SCP. Closing at a SCP near the far end of the
survey removes most of the error caused by azimuth misalignment.
NOTE
Position error, resulting from azimuth misalignment, grows with distance from
the starting point.
b. If it's not possible to close at a SCP near the far end of the survey, restrict the maximum radial distance
from the starting point to 50 Km.
NOTE
IPADS reduces azimuth misalignment as it surveys.
c.
Keep IPADS running between surveys, which also minimizes initialization time for subsequent surveys.
NOTE
IPADS reduces azimuth misalignment when the survey trajectory changes
direction, especially near the start of the survey.
d. Do not conduct surveys in a straight line. Changes in direction, especially near the beginning of a survey,
improve accuracy.
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