Radar Observer · ARPA — Vectors
Selecting TRUE vectors on an ARPA causes each tracked target to display a vector showing its:
- ARelative motion toward own ship
- BActual course and speed over the chosen ground/sea reference✓ Correct
- CRange and bearing only
- DEcho strength
Explanation
True vectors show each target's real course and speed (own ship also shows a true vector), useful for understanding the traffic picture and a target's intentions. Relative vectors show motion relative to own ship and point toward own ship if a target is on a collision course — better for spotting risk at a glance. Competent watchkeepers use both.
Authority: IMO Performance Standards for ARPA; Bowditch
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Related Radar Observer questions
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On an ARPA, a true vector displayed on a target shows the target's:
- ARPA — Vectors
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