Radar Observer · Plotting — The Plotting Triangle
In the radar transfer plot, the vector from O to A represents own ship's motion (reversed), the relative-motion line is the target's plotted track, and the vector WA gives the:
- AWind velocity
- BOwn ship's speed over ground
- CTarget's true course and speed✓ Correct
- DDistance to the nearest land
Explanation
In the standard plotting triangle, the e-r-m (or O-A-W) construction combines own ship's vector and the relative-motion vector to solve for the target's true vector — its actual course and speed. From the plot the navigator also obtains CPA, TCPA, and the aspect of the target.
Authority: Bowditch (Pub. No. 9), Radar Plotting
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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
The anti-clutter sea (STC / sensitivity-time control) is adjusted to: