Radio positioning systems using PHS terminals are provided as low-cost positioning services for logistics. In this research, a differential offset positioning methods for improving PHS positioning accuracy is proposed and its basic characteristics are evaluated. This method records position and RSSI data at major logistic points in advance and matches them with measured data of moving objects. For this purpose, a position evaluation method whose datum scattering area is small and a datum matching method which uses 3D space of latitude, longitude and RSSI are developed. Validity of the method is verified by the experiment at outdoor fields.
