JPS6431076A - Position measuring system - Google Patents

Abstract

PURPOSE:To obtain systems, by which many working ships can measure their positions individually, by using mobile stations are receive-only stations, transmitting radiowaves having the same frequency from fixed stations, and making the number of the mobile stations, which can utilize the radiowaves at the same time, indefinite. CONSTITUTION:A radiowave, which is continued fro a specified time, is sequentially transmitted from each fixed station at a constant timing. At this time, transmitting antennas 3, 5 and 7, which are provided at the fixed stations, transmit the radiowaves, which are modulated with superimposed signals of frequency signals for measuring lines of positions and frequency signals for recognizing lanes, into a service area (a). Synchronizing-radiowave transmitting antennas 1 and 2, which are provided at a master station that is one of the fixed stations, transmit position measuring radiowaves to slave stations (1) and (2) as synchronizing radiowaves. Synchronizing means 4a, 4b, 6a and 6b, which are provided at the slave stations (1) and (2) receive the synchronizing signals and transmit the position measuring signals having the same phase. Thus, mobile stations (b) receive the transmitted radiowaves and measure the difference in arriving times of the radiowaves. The position of each mobile station can be obtained based on the intersection of hyperbolic lines, whose foci are the two fixed stations.