Radar Observer · Performance — Range Scale Selection
Good watchkeeping practice for radar range-scale use in open water is to:
- AStay permanently on the 1.5 NM scale
- BPeriodically switch to a longer scale for early warning, then back to a working scale appropriate to traffic and proximity✓ Correct
- CUse only the longest scale at all times
- DChange scale only when a target is acquired
Explanation
Rule 7(b) calls for long-range scanning for early warning, but a very long scale loses close-in detail, so the watch keeps a working scale suited to the situation and regularly steps out to a longer one to detect new traffic early. Staying fixed on one scale risks either missing distant ships or losing close-quarters detail.
Authority: Navigation Rules Rule 7; Radar Observer curriculum
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