User manual

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To collect the measurements in the table, the housing was aligned to magnetic north
using a hand compass. Alignment to the other cardinal points was done by eye with reference to
marks on the bench. Variations in φ are caused by the small tilt of the bench surface and compass
calibration errors. Similarly, the variations in θ
H
from the expected heading are caused by
imperfect manual alignment and by compass calibration errors. The calibration errors, which
may be as large as 10 to 20, can be compensated for during post-processing using field data and
measurements collected during a spin test.
Appendix D-7