Celestial Navigation · Circle of Position
Why is a celestial line of position plotted as a straight line rather than the circle of equal altitude it really is?
- ABecause the circle of position has no center
- BBecause the Earth is treated as flat in celestial navigation
- CBecause Pub. 229 only produces straight lines
- DThe circle's radius (the zenith distance) is so large that a short arc near the assumed position is indistinguishable from a straight line✓ Correct
Explanation
A sight defines a circle of equal altitude centered on the body's geographic position, with radius equal to the zenith distance (often thousands of miles). Over the few miles near the assumed position, that huge arc is sensibly straight, so it is plotted as a tangent straight line.
Authority: Bowditch (Pub. No. 9), circle of equal altitude
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