A system for tracking the position of multiple objects in three dimensional space by transmitting radar interrogation signals having predetermined wave shapes to surface acoustic wave transducers attached to each object. Each transducer includes a unique electrically conductive pattern on one surface of a piezoelectric substrate for selectively responding to the predetermined wave shape of one of the interrogation signals for inducing a surface acoustic wave in the substrate and for thereafter transforming the surface acoustic wave into an electromagnetic response signal having detectable properties that uniquely identify said transducer. The location of each transducer is estimated by measuring the time-of-flight or angle-of-arrival of the radar signals at several measurement stations and producing a position estimate by triangulation.