Navigation General · Radar Plotting & CPA
In the standard radar relative-motion triangle (OAB), what does the vector 'WA' represent?
- AOwn ship's true course and speed over a plotting interval✓ Correct
- BThe target vessel's true course and speed
- CThe relative motion of the target (direction and speed of approach)
- DThe vector from CPA back to own ship's present position
Explanation
In the OAB (or WA-AB-WB) relative-motion triangle: WA is own ship's true velocity vector (course and speed) drawn from the origin W; AB is the target's true velocity vector; and WB is the relative velocity vector (the direction and rate at which the target approaches own ship). The relative-motion line from the target's successive plotted positions yields the same vector WB.
Authority: Radar Navigation Manual (Pub. 1310), Ch. 4
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