Celestial Navigation · Compass Error
Compass error found by an azimuth or amplitude observation is the combination of:
- AIndex error and dip
- BVariation and deviation✓ Correct
- CRefraction and parallax
- DLatitude and longitude
Explanation
Comparing the true bearing/azimuth of a body to its compass bearing gives compass error, the algebraic sum of variation (from the chart) and deviation (from the vessel's magnetism). Subtracting known variation isolates deviation.
Authority: Bowditch (Pub. No. 9), compass checks
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