A key development was the cavity magnetron in the United Kingdom, which allowed the creation of relatively small systems with sub-meter resolution. Radar was developed secretly for military use by several countries in the period before and during World War II. Radio waves (pulsed or continuous) from the transmitter reflect off the objects and return to the receiver, giving information about the objects' locations and speeds.

A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects.

It is used to detect and track aircraft, ships, spacecraft, guided missiles, and motor vehicles, and map weather formations, and terrain. Radar is a radiolocation system that uses radio waves to determine the distance ( ranging), angle ( azimuth), and radial velocity of objects relative to the site. It rotates steadily, sweeping the airspace with a narrow beam. Radar of the type used for detection of aircraft.

Navy radar world war 2