Marine radars are used to detect other ships & land obstacles, and to provide bearing and distance for collision avoidance and navigation at sea. They are electronic navigation instruments that use a rotating antenna to sweep a narrow beam of microwaves around the water surface surrounding the ship to the horizon, detecting targets by microwaves reflected from them, and displaying a picture of the ship's surroundings on a display screen.

Radar is a vital component for safety at sea and near the shore. Captains need to be able to maneuver their ships in adverse conditions and to be able to navigate "blind" when there is no visibility at night or due to bad weather.