Radiolocation

Radiolocation is the technique of determining the position, distance, or movement of objects by using radio waves. It encompasses systems that actively emit radio signals to detect targets (radar) as well as methods that determine location by exploiting existing radio transmissions (radio direction finding and multilateration).

Principles involve transmitting or receiving radio waves and measuring how they interact with targets. Range is estimated from time of flight or phase differences, bearing from angle of arrival or interferometry, and velocity from Doppler shift. Different implementations use pulsed, continuous-wave, or frequency-modulated signals. Technical choices include antenna design, signal processing, and error compensation to improve accuracy and resolution.

Active radiolocation uses a transmitter and receiver to detect targets, as in radar, weather radars, and naval ships; passive radiolocation uses reflections, beacons, or existing emissions to locate sources, often without transmitting. Systems are deployed across military, civilian, and scientific contexts, from air traffic control to meteorology.

Common techniques include time-of-flight, time-difference-of-arrival, and multilateration for ranging; angle-of-arrival and interferometry for direction finding; and frequency-modulated continuous wave or pulse-compression methods for high-resolution range. Many systems rely on arrays and digital signal processing to enhance accuracy and resolve multiple targets.

Applications span aviation, maritime navigation, weather observation, military surveillance, search and rescue, and telecommunications. Public and commercial techniques, including radar-based navigation and satellite radio navigation, rely on radiolocation principles for positioning and tracking. The field continues to evolve with advances in sensor fusion, high-frequency bands, and space-based receivers.