1. A method comprising: (a) receiving a signal-strength measurement for a signal that traverses a path between a first radio and a second radio; (b) generating an estimate of the location of said first radio, wherein said estimate of the location of said first radio is based on: (i) said signal-strength measurement, and (ii) a path-loss map that is indicative of the path loss between the location of said second radio and a non-empty set S of locations; wherein said path-loss map is based on a path-loss model; and wherein said path-loss model is based on a matrix that comprises at least one non-cardinal number.