| 摘要 |
A geographic tracking system (10) with minimal power and size required at th e mobile terminal (18) collects observation data at the mobile terminal (18), forwards the data to a processor (11), which calculates the position. The mobile terminal (18) needs only to gather a few milliseconds of observation data (from 14-17), and to relay this observation data to the processor (11). The range from the satellite (13) (or other airborne transponder) to the terminal (18) is determined using the known positions of an interrogating transmitter and a satellite (13), and a known terminal delay between the received signal and the transmission of the return signal, and the round tri p time. An arc of locations is determined by computing an intersection of a sphere centered at the satellite (13) having a radius given by the calculate d range with a model of the Earth's surface. The candidate points are consider ed and refined using code phase measurements from a set of GPS satellites (14- 17). The candidate point having the lowest residuals or expected to measured code phases is chosen as the location of the mobile terminal (18). The measurements can be refined to account for various sources of error includin g measurement bias, relative motion and timing errors. |
