RADAR COMMUNICATION

Radar is an object-detection system that uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft  ships, spacecraft, guided missiles ,motor vehicle weather formations, and terrain. The radar dish (or antenna) transmits pulses of radio waves or microwaves  that bounce off any object in their path. The object returns a tiny part of the wave's energy to a dish or antenna that is usually located at the same site as the transmitter.
Radar was secretly developed by several nations 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.^[ The term radar has since entered English
and other languages as a common noun, losing all capitalization.
The modern uses of radar are highly diverse, including air traffic control, radar astronomy, air-defense 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; and ground-penetrating radar for geological observations. High tech radar systems are associated with digital signal processing and are capable of extracting useful information from very high noise levels.

Radar at work

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.