An apparatus and method for building a base station almanac at a non-carrier location server is shown. A mobile device cooperates by informing the non-carrier location server of observed time difference of arrival (OTDOA) assistance data it receives. The non-carrier location server collects enough OTDOA assistance data through crowd souring or spoofing to generate an OTDOA library. The non-carrier location server using the OTDOA library to generate a base station almanac. Once created, non-carrier location server uses the base station almanac to provide assistance data to mobile devices without assistance from the carrier. Also, a mobile device may use the base station almanac to determine transmission timing between itself and neighboring and distant base stations.