Agps server with sbas aiding information for satellite based receivers

A satellite navigation system assistance server, comprising:

• an Internet presence accessible to client satellite navigation system receivers;
• a plurality of SBAS reference receivers for strategic location around the world, and each one corresponding to and configured to receive and process SBAS broadcasts from one of the independent WAAS, EGNOS, MSAS, and GAGAN SBAS systems;
• an SBAS accumulator for collecting corresponding SBAS messages from the plurality of SBAS reference receivers, and for computing GNSS satellite vehicle (SV) health, DGPS information, SBAS ephemeris and almanac;
• a PRN processor for identifying the SV's according to their assigned pseudorandom number (PRN) modulation codes, and for forwarding the appropriate PRN masks for particular clients according to the SBAS satellites visible to their respective places around the world;
• a PRN database for storing information generated by the SBAS accumulator and the PRN processor, according to the PRN's of corresponding SV's;
• and
• a client request processor for responding to clients over the Internet who supply at least a general idea of their present location and that require pertinent GNSS information as to SV health, DGPS information, and SBAS ephemeris and almanac, and for providing an appropriate PRN mask from the PRN database;
• wherein, the satellite navigation system assistance server is configured to reply to client requests that include an indication of the client's location, and if an accurate location is included in the server request, the satellite navigation system assistance server computes which particular SBAS systems are observable to the requesting client, and in this case the satellite navigation system assistance server limits its replies to pertinent information for a more compact response message.