noun
trilateration
Technical term in surveying and geodesy: determining a position by measuring the lengths of the three sides of a triangle, as opposed to triangulation which uses angles.
GPSの位置測定には三辺測量の原理が使われている。
The principle of trilateration is used in GPS positioning.
Triangulation measures angles, while 三辺測量 measures side lengths.
Compound of 三辺 (three sides) and 測量 (surveying, measurement).