Abstract : A relative position indicator (RPI) system with radial antenna array (RAA) is proposed and experimentally demonstrated for use in a tracking-based position estimation system (PES). Utilizing radial vectors generated by both received signal strength (RSS) and azimuth direction of each antenna element in the RAA, accurate direction and distance-to-target can be obtained simultaneously. The proposed RPI system using a radial vector sum and a simple equalization process can mitigate the gain mismatch problem, which was a serious problem in previous tracking-based PESs.