Navigation General · Piloting
A 'fix by depth contour' is most useful when:
- AThere are many charted landmarks visible
- BVisibility is poor but a distinct, steep depth contour can be followed or crossed and matched to the chart✓ Correct
- CThe water is uniformly deep
- DThe vessel is at anchor
Explanation
Where a well-defined depth contour exists, crossing it (noted by the echo sounder) provides an LOP, and running soundings along it can confirm position when landmarks are obscured. It is a valuable backup in reduced visibility.
Authority: Bowditch (Pub. 9); piloting by soundings
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