multilateration

Multilateration is a position‑finding technique that estimates the location of a transmitter by measuring signals received at multiple fixed stations with known coordinates. By exploiting differences in signal arrival times, the system constrains the transmitter's position in two or three dimensions.

Two common modes are TOA‑based and TDOA‑based multilateration. TOA requires synchronized clocks at the stations and the transmitter's absolute emission time; each station yields a sphere of possible locations. TDOA uses only the differences in arrival times between station pairs, eliminating the need to know the transmitter time, and defines hyperbolic loci whose intersection gives the position.

In practice, at least three stations are needed for 2D positioning and four for 3D positioning, with accuracy improving as more stations are added and as clock synchronization improves.

Applications include air traffic surveillance, cellular and wireless network positioning, emergency location services, and indoor localization using Wi‑Fi or beacons. Accuracy depends on geometry, clock synchronization, measurement noise, and propagation conditions; typical ranges span meters to tens of meters, though advanced systems can be more precise.

Multilateration is related to trilateration but differs in handling unknown timing: it relies on time differences rather than absolute distances. It is often used to complement satellite navigation and to extend coverage where GPS is unavailable or unreliable.