1. A method of determining the geolocation of a mobile device operating in a region served by a communications network, the method comprising the steps of: (a) determining, in observation space, an observation cluster of measurement data from a first set of network measurement reports (“NMRs”) from the communication network; (b) comparing measurement data from a candidate NMR for a mobile device with the determined observation cluster of measurement data; and (c) determining a location of the mobile device as a function of the compared measurement information.