Systems and methods for enhanced broadcast ephemeris are described. These systems and methods comprise the calculation and transmission of globally and locally optimized parameters of the broadcast ephemeris of a global navigation satellite system, such as ionosphere, clock, and orbital parameters of a GPS satellite and receiver. The locally-optimized satellite clock parameter compensates for geographically- specific signal errors that cannot be compensated by any global parameter of the broadcast ephemeris. The enhanced broadcast ephemeris error corrections are transmitted in the conventional RINEX format.

Methods, systems and computer program products for broadcasting location information through out of band service mechanism such as SMS are described. Specifically, ephemeris assist information, which may contain a datafile of geographic location(s) over a period of time validity, and which may contain information associated with operational satellites in a ephemeris interval, predicted ephemeris interval or any number of subsequent predicted ephemeris intervals may be used to identify a geographic location of a device. The ephemeris assist information may subsequently be broadcast to the device using one or more messages.

Satellites of a satellite positioning system broadcast within the navigation signals ephemeris data having a certain period of validity. At a mobile station, ephemeris data are required for position-fixing. In assisted satellite positioning systems, acquisition of navigation signals emitted by the satellites is facilitated as assistance data are provided to the mobile station. At a server station, a request for assistance data issued by said mobile station is received, and the server station transmits ephemeris data as part of the assistance data to the mobile station in response to its request. Upon receiving the request for assistance data issued by said mobile station, the server station decides whether the mobile station could achieve a specified position fix accuracy if the mobile station was provided with the broadcast ephemeris data. In the positive, the server station transmits the broadcast ephemeris data to the mobile station. In the negative, the server station transmits, instead of broadcast ephemeris data, long-term ephemeris data to the mobile station as part of the assistance data requested. The long-term ephemeris data are derived from satellite orbit predictions and have a period of validity substantially increased with respect to the ephemeris data broadcast by the satellites.