Radar Observer · ARPA — Acquisition
An ARPA derives a target's true course and speed by:
- AA single radar observation
- BTracking successive positions over time and computing the vector with own-ship input✓ Correct
- CReading the target's AIS only
- DMeasuring echo brightness
Explanation
ARPA acquires a target and tracks it over several scans, combining the changing range/bearing with own ship's course and speed to compute the target's true motion, CPA, and TCPA. It needs time (typically about 3 minutes) for a steady solution.
Authority: Radar Navigation — ARPA
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Related Radar Observer questions
- Display — Motion
On a relative-motion radar display, your own ship is:
- Collision Avoidance — CPA
The closest point of approach (CPA) of a radar target is:
- Collision Avoidance — TCPA
TCPA on a radar/ARPA readout represents the:
- Controls — EBL
The electronic bearing line (EBL) on a radar is used to:
- Controls — VRM
The variable range marker (VRM) on a radar measures:
- Controls — Clutter
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