A mobile GPS-aiding system uses a GPS reference receiver to collect GPS navigation messages, a GPS-aiding data network server to distribute over the Internet all ephemeris and almanac data gleaned from the navigation messages, a number of commercial broadcast radio stations to publish such ephemeris and almanac data on particular sub-carriers, a number of vehicles equipped to receive the radio broadcasts and the sub-carriers and to retransmit them locally, e.g., via Bluetooth. Portable GPS receivers, operated near any of the vehicles, a receive Bluetooth transmissions with the ephemeris and almanac data with the identity of the radio broadcast station then being tuned. A breadcrumb database is used to index the locations of the radio broadcast stations. Each mobile GPS receiver contributes to such database after it computes a location fix. If the location of the radio broadcast station is already known to the database, then the location can be accessed and used before finding a position solution.