1. A method of determining the location of a mobile device in a geographic region comprising the steps of: (a) providing calibration data for each of one or more calibration points in a geographic region, said calibration data having one or more characterizing parameters; (b) generating one or more sets of grid points for said calibration data; (c) receiving at least one network measurement report from a mobile device at an unknown location in said geographic region; (d) evaluating said at least one network measurement report with each of said sets of grid points as a function of select ones of said characterizing parameters; (e) selecting a set of grid points as a function of a predetermined criteria; and (f) determining the location of a mobile device in said geographic region as a function of said selected set of grid points.