Patent ID: 7301498

Claim:
A method for positioning a device, comprising: performing measurements to determine at least the range between a first positioning station and the device and to determine at least the range between a second positioning station and the device, and in which at least one measurement defines a geometric, quadratic surface for the position of the device, and which first positioning station and second positioning station belong to different systems, selecting as a geometric model a set of surfaces having common points of intersection such that the position of the device is at least one of the common points of intersection and making the selection on the basis of the measurements, the model comprising, at the most, quadratic surfaces, simplifying the selected geometric model to reduce the number of quadratic surfaces, to provide a simplified geometric model, but leaving at least one quadratic surface without linearization, selecting a maximum number of measurements to be used in the simplified geometric model, said maximum number corresponding to the minimum number of measurements required to determine the position, inserting the measurement results in the simplified geometric model, and determining the position of the device by solving the simplified geometric model.