To reduce the effects due to a multipath or a height pattern, and accurately detect the distance or the direction although the detection accuracy is excessively degraded by the effect due to the multipath or the height pattern, if the distance or the direction is detected by utilizing ultrasonic signal, a high-frequency signal or an optical signal.

In either or both of transmitting means or relay means fixed or carried by a moving body, or a plurality of antennas installed in the vicinity of a receiving means, or an antenna of the transmitting means or the relay means connected to a plurality of wave-transceiving devices, or a fixed receiving means synchronized with an individual system synchronization signal from the wave-transceiving device or periodically transmitting a plurality of orthogonal measurement signals, or a receiving means carried by the moving body, the direction is detected accurately by receiving the system synchronization signal, sensing relative distances and the direction and detecting the direction from an average of shorter relative distances.