1. In a wireless location finding system, a computer-implemented method for determining a geographical location from a measured wireless signal signature, the method comprising: calculating from the measured wireless signal signature a multi-dimensional vector v, wherein each component of v measures a degree of coincidence between the measured wireless signal signature and a calibrated signal signature stored in a calibration table; matching v with matched vectors in a set of multi-dimensional calibrated vectors v.sub.1,. .. , v.sub.N, using a procedure comprising searching a hierarchical tree structure containing the calibrated vectors v.sub.1,. .. , v.sub.N, and selecting the matched vectors from leaf nodes in the tree, where the matched vectors correspond to calibrated geographical locations.