Location Fix From Unknown Position

摘要

An apparatus configured to determine a region of the Earth's surface within which a receiver is located. The method of use comprises identifying a plurality of satellites from which that receiver is receiving signals and determining a region of the Earth's surface from which it is possible to simultaneously receive signals from the plurality of satellites. The overlapping signal reception areas from each visible satellite allow a rough estimation of the location of the receiver to be made. To further restrict the approximate location of the receiver, a Doppler fix based on the received satellite signals can be performed, or a visibility horizon associated with the satellite positions relative to the receiver can be computed.