초록 ▼

A method and system for determining the position of an object using a fixed station and a plurality of earth orbit satellites whose positions are known. Separate periodic signals are transmitted from the fixed station via first and second satellites to the object whose postion is to be determined. T

A method and system for determining the position of an object using a fixed station and a plurality of earth orbit satellites whose positions are known. Separate periodic signals are transmitted from the fixed station via first and second satellites to the object whose postion is to be determined. The phase offset in periodic characteristics of the periodic signals as received from the first and second satellites is measured at the object. The phase offset corresponds to a relative time difference in propagation of the signals traveling two different paths to the object. The object transmits via the first satellite a return signal indicative of the measured relative time difference. This return signal is activated some time in the future according to the object local time, which is slaved to receipt of the periodic signal sent through the first satellite. This future time is the start of the particular time period as decided by the fixed station\s schedule. At the fixed station, an instantaneous round trip delay, determined by the time offset of the current transmission clock time relative to the receive clock time of reception of the return signal, along with the measured relative time difference sent back on the return signal, is used to calculate the distances between the first and second satellites to the object. From these distances the position of the object is calculated.

대표청구항 ▼

A method for determining the position of an object in a reference coordinate system using a fixed station and a plurality of earth orbit satellites wherein the positions of said fixed station and said satellites are known in said reference coordinate system with respect to a reference point and the

A method for determining the position of an object in a reference coordinate system using a fixed station and a plurality of earth orbit satellites wherein the positions of said fixed station and said satellites are known in said reference coordinate system with respect to a reference point and the distances from said fixed station to said satellites are also known, said method comprising the steps of: transmitting from said fixed station a forward periodic signal synchronized to a fixed station transmission clock via first and second satellites to an object whose position is to be determined; receiving at said object said forward periodic signal; synchronizing at said object an object clock to said received forward periodic signal transmitted via said first satellite; measuring at said object a first relative time difference in said forward periodic signal as transmitted via said first and second satellites and received at said object; transmitting from said object to said fixed station via said first satellite a return signal synchronized with said object clock and modulated with information indicative of said first relative time difference; receiving at said fixed station said return signal; synchronizing at said fixed station a fixed station reception clock to said received return signal; measuring at said fixed station a second relative time difference between said fixed station transmission and reception clocks; calculating at said fixed station, from said first and second relative time differences, respective distances from said first and second satellites to said object; and computing the position of said object in said reference coordinate system.