NAV-RADAR-L1.1

Radar navigation and interpretation

Radar is a primary tool for navigation and collision avoidance, especially in poor visibility, and using it well starts with setting it up and reading the picture. This lesson covers radar use and interpretation.

Entry & progression

Course: radar navigation, radar plotting and the use of ARPA at the operational and management levels — required for deck officers using radar for navigation and collision avoidance. Entry: deck officer or trainee. Supports the deck CoC pathway (OOW at operational, Master/Chief Mate at management level).

Reading the radar

  • Set the radar up correctly: the gain, the sea and rain clutter, the range scale and the tuning.
  • Understand the radar picture, target detection, and the factors that limit it.
  • Use radar for position fixing — ranges and bearings — and for parallel indexing along a track.
  • Recognise false echoes, blind and shadow arcs, and the effect of weather on detection.

A radar is only as good as its setup: the gain and the sea and rain clutter controls must be adjusted for the conditions, because over-suppressing clutter can erase small targets while too little leaves the screen unreadable. The officer interprets the picture, using ranges and bearings to fix position and parallel index lines to monitor the track past a danger, while recognising the false echoes and blind arcs that can mislead. Radar earns its keep in poor visibility, when the eyes cannot see.

WARNING — Clutter suppression can hide targets Over-using the sea or rain clutter control can erase small targets close to the ship — a yacht, a buoy, a small craft. Tune the radar to see the contacts, not just to produce a clean screen.

TIP — Set it up for the conditions Gain, sea clutter and rain clutter are adjusted for the actual conditions and re-checked as they change. A radar left on automatic in difficult returns can miss the target that matters.

Practice questions

5 questions
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Excessive use of the sea-clutter control on radar can: (a) Improve small-target detection (b) Suppress and hide small targets close to the ship (c) Increase the range scale (d) Change the compass

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Radar is especially valuable in: (a) Clear daylight only (b) Poor visibility, when the eyes cannot see (c) Harbour only (d) Calm weather only

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Parallel indexing is used to: (a) Measure the tide (b) Monitor the ship's track relative to a danger or mark (c) Charge the battery (d) Correct the compass

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Position can be fixed by radar using: (a) Colour only (b) Ranges and bearings to identified objects (c) The clock (d) The wind

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Gain and clutter controls should be: (a) Left on automatic always (b) Adjusted for the conditions and re-checked as they change (c) Turned to maximum (d) Ignored

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