In 1895, Alexander Popov, a physics instructor at the Imperial Russian Navy school in Kronstadt, developed an apparatus using a coherer tube for detecting distant lightning strikes. Main article: History of radar First experiments Īs early as 1886, German physicist Heinrich Hertz showed that radio waves could be reflected from solid objects. With the emergence of driver-less vehicles, radar is expected to assist the automated platform to monitor its environment, thus preventing unwanted incidents. One example is lidar, which uses predominantly infrared light from lasers rather than radio waves. Other systems similar to radar make use of other parts of the electromagnetic spectrum. Modern high tech radar systems use digital signal processing and machine learning and are capable of extracting useful information from very high noise levels. The modern uses of radar are highly diverse, including air and terrestrial traffic control, radar astronomy, air-defense systems, anti-missile systems, marine radars to locate landmarks and other ships, aircraft anti-collision systems, ocean surveillance systems, outer space surveillance and rendezvous systems, meteorological precipitation monitoring, altimetry and flight control systems, guided missile target locating systems, self-driving cars, and ground-penetrating radar for geological observations. The term radar has since entered English and other languages as a common noun, losing all capitalization. The term RADAR was coined in 1940 by the United States Navy as an acronym for radio detection and ranging. 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.

Pinpoint doppler radar