Radar (Radio Detection and Ranging) is a shipboard navigation instrument that transmits radio wave pulses and measures their reflection off objects to determine range and bearing. Every commercial vessel is required to carry radar under SOLAS.
How It Works
The radar transmits a directional radio pulse, then listens for the pulse to bounce back off a target (another ship, land, a buoy). The time delay gives range; the antenna’s direction at the moment of reflection gives bearing. This builds a real-time picture of everything reflecting radar waves around the vessel, displayed on a screen.
Why It Matters
- Collision avoidance — detecting other vessels’ range, bearing, and course well before visual sighting, especially critical at night or in fog
- Navigation — identifying coastlines, buoys, and other fixed references for position-fixing
- Works in poor visibility — unlike visual lookout, radar functions in fog, heavy rain, and darkness
ARPA
Most modern marine radars are ARPA (Automatic Radar Plotting Aid) sets, which automatically track detected targets and calculate their course, speed, Closest Point of Approach (CPA), and Time to Closest Point of Approach (TCPA) — critical data for collision avoidance decisions under COLREGs.
Exam Relevance
Radar and ARPA operation, plotting, and collision-avoidance decision-making are core competency exam topics for both 2nd Mate FG and Master FG, tested in both written papers and practical simulator assessments.