What Is Radar?
Radar, or radiolocation, as it was called in the early days, is the use of radio waves to find the whereabouts of aircraft or ships. Electromagnetic waves, which include radio and light waves, all travel at the same speed. When small bursts of radio waves, fired into space from a transmitter, strike an object such as an aircraft some of them bounce back and are collected by an aerial. Special equipment calculates the distance of the object from the time taken for the waves to go there and back. Direction is obtained by rotating the aerial, and the course being taken by the object is shown as spots of light on the face of a cathode ray tube.
So direction, position and movement can be judged accurately. Radar was first used to detect enemy aircraft in wartime, and to guide fighter aircraft and bomber pilots. Since then it has proved invaluable in civil aviation by helping the pilot to guide his aircraft in the air and to land it safely in fog or at night. At sea it can give the position of land and other ships. Some buoys are fitted with radar, so that they can be located in the dark or in fog. Radar is used also to give warning of turbulent weather.
The modern uses of radar are highly diverse, including air and terrestrial traffic control, radar astronomy, air-defence systems, antimissile systems, marine radars to locate landmarks and other ships, aircraft anticollision systems, ocean surveillance systems, outer space surveillance and rendezvous systems, meteorological precipitation monitoring, altimetry and flight control systems, guided missile target locating systems, ground-penetrating radar for geological observations, and range-controlled radar for public health surveillance. High tech radar systems are associated with digital signal processing, machine learning and are capable of extracting useful information from very high noise levels.
Other systems similar to radar make use of other parts of the electromagnetic spectrum. One example is “lidar”, which uses ultraviolet, visible, or near infrared light from lasers rather than radio waves. The information provided by radar includes the bearing and range (and therefore position) of the object from the radar scanner. It is thus used in many different fields where the need for such positioning is crucial.
Radar was developed secretly for military use by several nations in the period before and during World War II. The term RADAR was coined in 1940 by the United States Navy as an acronym for RAdio Detection And Ranging or RAdio Direction And Ranging. The term radar has since entered English and other languages as a common noun, losing all capitalization.
In aviation, aircraft are equipped with radar devices that warn of aircraft or other obstacles in or approaching their path, display weather information, and give accurate altitude readings. The first commercial device fitted to aircraft was a 1938 Bell Lab unit on some United Air Lines aircraft. Such aircraft can land in fog at airports equipped with radar-assisted ground-controlled approach systems in which the plane’s flight is observed on radar screens while operators radio landing directions to the pilot.
Marine radars are used to measure the bearing and distance of ships to prevent collision with other ships, to navigate, and to fix their position at sea when within range of shore or other fixed references such as islands, buoys, and lightships. In port or in harbour, vessel traffic serviceradar systems are used to monitor and regulate ship movements in busy waters.
Meteorologists use radar to monitor precipitation and wind. It has become the primary tool for short-term weather forecasting and watching for severe weather such as thunderstorms, tornadoes, winter storms, precipitation types, etc. Geologists use specialized ground-penetrating radars to map the composition of Earth’s crust. Police forces use radar guns to monitor vehicle speeds on the roads. Smaller radar systems are used to detect human movement. Examples are breathing pattern detection for sleep monitoring and hand and finger gesture detection for computer interaction. Automatic door opening, light activation and intruder sensing are also common.