Patent ID: 8730105

Claim:
A method of determining the position of a mobile terminal having a receiver for receiving signals from a plurality of transmission sources where one or more of the transmission sources are at unknown positions, the mobile terminal also having an independent positioning device able to find, when operative, the position of the mobile terminal, the method comprising the steps of using said independent positioning device, measuring the position of the mobile terminal at one or more first locations; measuring by the mobile terminal, at each first location, a respective first set of relative time or phase offset values of signals received from the transmission sources relative to each other or to a reference in the mobile terminal, where the position of one or more of these transmission sources is unknown; calculating transmission time offsets of the signals transmitted by said transmission sources using the measured position at said one or more first locations and said respective first sets of relative time or phase offset values of signals received from the transmission sources; measuring by the mobile terminal, at a second terminal location where said independent positioning device is not operative, a second set of relative time or phase offset values of the signals received from the transmission sources, relative to each other or to a reference in the mobile terminal, where the position of one or more of these transmission sources is unknown; and combining said second set of relative time or phase offset values and the calculated transmission time offsets, and thereby calculating by the mobile terminal the position of the mobile terminal at the second location.