Position determining system

PCT No. PCT/GB96/02308 Sec. 371 Date Mar. 17, 1998 Sec. 102(e) Date Mar. 17, 1998 PCT Filed Sep. 16, 1996 PCT Pub. No. WO97/11384 PCT Pub. Date Mar. 27, 1997The invention relates to a position determining system, for receiving digital telephone signals transmitted by a number of transmission sources BTS. The system has a pair of receiving stations, CBU and CRU, one at a known position O and another on a roving object R; a position determining processor CPP; and means for passing a link signal, L1 and L2, from each of the receiving stations to the position determining processor, the link signal containing information about the signals received at the receiving station from the transmission sources. Each of the receiving stations is arranged to receive the signals from the respective transmission sources substantially simultaneously. The position determining processor is arranged to compare the information received from the one receiving station with the information received at the other receiving station, and to determining the time delay between the respective signals received at both receiving stations in order to determine the position of the roving object.