Patent ID: 7990314

Claim:
A method of positioning, comprising: one or more receivers receiving FM stereo signals from three FM stations, said stereo signal including a FM modulated 19 KHz pilot tone, wherein one of the receivers is a mobile unit (MU) comprising a FM stereo receiver, a processor and a transceiver; said receivers performing phase bias corrections for the demodulated pilot tones in the FM signals to obtain phase corrected pilot tones; the mobile unit receiving phase biases corrections from either base station or reference station, and measuring phase differences between the pilot tones; the mobile unit performing two way communications to transmit phase measurement pairs to the base station or the reference station; determining a geographical position at a receiver from the phase corrected pilot tones by performing Time Difference of Arrival (TDOA) hyperbolic triangulation and; determining a geographical position at the mobile unit based on the measured phase differences with received phase biases corrections.