Radiopositioning

Radiopositioning is the process of determining geographic position using radio waves from fixed transmitters or satellites. It relies on measuring properties of radio signals such as travel time, phase, angle, or signal strength, to infer distance or direction to known reference points.

The primary methods include time-based ranging (TOA, TDOA) and multilateration, which compute a position from measured distances to multiple transmitters. Another approach uses signal strength measurements (RSSI) or fingerprinting, comparing observed signal signatures to a pre-surveyed map. Angle of arrival (AOA) uses antenna arrays to estimate the direction of signals. Modern systems often combine techniques to improve reliability, especially indoors where signals are degraded.

Key technologies include satellite-based radiopositioning such as GNSS (GPS, GLONASS, Galileo, BeiDou), which provide outdoor positioning via coordinated time signals. Terrestrial approaches include legacy systems like LORAN, but more common today are cellular network positioning (cell-ID, OTDOA), Wi-Fi fingerprinting, Bluetooth beacons, and ultra-wideband (UWB) ranging. Indoor positioning often relies on Wi-Fi, Bluetooth, UWB, and sometimes RFID.

Accuracy varies widely. GNSS in open areas yields meters-level accuracy; indoor and urban environments may require Wi‑Fi, BLE, or UWB to achieve meter to decimeter precision. Applications span navigation, vehicle tracking, logistics, robotics, emergency response, and location-based services.

Challenges include multipath propagation, non-line-of-sight conditions, clock synchronization, interference, and privacy concerns. Ongoing developments combine multiple radio technologies with inertial sensors and map data to improve reliability, especially in challenging environments, and next-generation networks aim to enhance positioning in urban canyons and indoors.