초록 ▼

A geographic tracking system with minimal power and size required at the mobile terminal collects observation data at the mobile terminal, forwards the data to a processor, which calculates the position. The mobile terminal needs only to gather a few milliseconds of observation data, and to relay th

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

대표청구항 ▼

1. A location determination system, comprising a communication satellite;a mobile terminal, including a processor that controls a collection of code phase measurements from signals received from a plurality of GPS satellites, and an identification of an area of interest from a terrestrial based wire

1. A location determination system, comprising a communication satellite;a mobile terminal, including a processor that controls a collection of code phase measurements from signals received from a plurality of GPS satellites, and an identification of an area of interest from a terrestrial based wireless signal communicating over said area of interest in which said mobile terminal resides, said area of interest being smaller than a convergence zone area, wherein a size of said convergence zone area is a size of an area around a current location of a mobile terminal in which an initial position point must lie to guarantee that an iterative position calculation starting with said initial position point will converge to said current location of said mobile terminal, anda transmitter for transmission of said code phase measurements and said identification of said area of interest to said communication satellite; anda service operations center that receives said plurality of code phase measurements and said identification of said area of interest from said communication satellite, said service operations center including a position calculation module that iteratively calculates a position solution using said plurality of code phase measurements starting with a selected initial position point in said area of interest, wherein identification of said area of interest guarantees that a final position point produced by said position calculation module, after starting with said selected initial position point, is said current location of said mobile terminal, wherein said position calculation module performs an iterative calculation on only a single candidate location point. 2. The system of claim 1, wherein said area of interest is a city. 3. The system of claim 1, wherein said iterative calculations are based on a least squares algorithm. 4. The system of claim 1, wherein said convergence zone area has a radius less than 80 km. 5. A location determination system, comprising a communication satellite;a mobile terminal, including; a processor that controls a collection of measurements from signals received from a plurality of GPS satellites, anda transmitter for transmission of said measurements and an indication of an area of interest in which said mobile terminal resides to said communication satellite, said area of interest being smaller than a convergence zone area, wherein a size of said convergence zone area is a size of an area around a current location of a mobile terminal in which an initial position point must lie to guarantee that an iterative position calculation starting with said initial position point will converge to said current location of said mobile terminal; anda service operations center that receives said plurality of measurements and said indication of said area of interest from said communication satellite, said service operations center including a position calculation module that iteratively calculates a position solution using said plurality of measurements starting with an identified position point in said area of interest, wherein identification of said area of interest guarantees that a final position point produced by said position calculation module, after starting with said identified position point, is said current location of said mobile terminal, wherein said position calculation module performs an iterative calculation on only a single candidate location point. 6. The system of claim 5, wherein said area of interest is a city. 7. The system of claim 5, wherein said iterative calculations are based on a least squares algorithm. 8. The system of claim 5, wherein said convergence zone area has a radius less than 80 km. 9. The system of claim 5, wherein said measurements are code phase measurements.