Patent ID: 7286835

Claim:
A method for estimating the location of a wireless node relative to a plurality of radio receivers operative to detect the strength of radio frequency (RF) signals, wherein a RF coverage map, corresponding to each of the radio receivers, characterizes the signal strength values for locations in a physical region, comprising collecting signal strength values, detected at a plurality of radio receivers, corresponding to signals transmitted by a wireless node; and determining a differential error surface comprising, for all unique pairs of radio receivers of the plurality of radio receivers, the sum of the squares of the difference between the signal strength values detected by a pair of radio receivers less the difference between the signal strength values in the RF coverage maps associated with the pair of radio receivers; and estimating the location of the wireless node using the differential error surface wherein estimating the location of the wireless node further comprises: computing, for each radio receiver, an individual error surface based on the RF coverage map associated with the radio receiver and the signal strength detected by the radio receiver; aggregating the individual error surfaces to create a total absolute error surface; adding the total absolute error surface and the differential error surface; and selecting a location based on the results of the adding step.