Skybitz, Inc.

Eagle-eye, Inc.

James B Kilfeather

Mark C Sullivan

Jay Brosius

Richard Burtner

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. In one embodiment, the observation data is communicated to the processor using either a satellite communication network or through a mobile telephone network.

System and method for dual-mode location determination

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.

System and method for fast acquisition position reporting

System and method for fast acquisition reporting using communication satellite range measurement

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. Alternatively, candidate locations that are consistent with the carrier signal received from GPS satellites can be used. In either case, 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.

System and method for rapid telepositioning

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. Only that portion of the arc within the region bounded by the satellite beam pattern is retained. Next, the time when the mobile terminal collected the GPS signal is determined. A satellite orbit model estimates the positions of the GPS satellites at their time of transmission. Using discrete points on the arc as an initial guess, an iterative least squares technique fits the observation data to the predicted data and minimizes residual error. After convergence, this estimated position solution is then screened against the known satellite range, satellite beam boundaries, an acceptable altitude range, and a maximum residual threshold. Those position estimates not meeting these criteria are discarded. The remaining points are then subjected to a final improved position estimate and residual calculation and the best point is selected.

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Purcellville, VA, United States of America

James B Kilfeather