Celestial Navigation · Compass Error
The primary navigational use of an amplitude observation is to:
- ADetermine the vessel's latitude
- BFind the time of meridian passage
- CDetermine compass error by comparing the observed and true amplitude✓ Correct
- DMeasure the height of tide
Explanation
The true amplitude is computed from the body's declination and the observer's latitude. Comparing it with the bearing read off the compass when the body is on the horizon yields the compass error (and, with variation known, the deviation).
Authority: Bowditch (Pub. No. 9)
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