A method and apparatus for generating reference signatures for use in geolocation in a cellular wireless communication system is provided. A first signature for a mobile communication unit comprises location information, a timestamp, and radio frequency measurement information obtained by a mobile communication unit at a location, but does not contain identification information for the mobile communication unit. The first signature is compared to signatures in a database, to identify a second signature that has a timestamp and radio frequency measurement information that correspond to those of the first signature. A reference signature is created by combining at least a part of the first signature with at least a part of the second signature. Repetition of the comparison and combination steps creates a database of reference signatures, for use in geolocating other received call signatures.