Method and apparatus for predicting the position of a satellite in a satellite based navigation system
First Claim
1. A method for determining the position of a satellite in a satellite based navigation system using a receiver having a known position, the method comprising the steps of:
- (a) receiving, from the satellite, a plurality of navigation signals at the receiver;
(b) determining a plurality of mean satellite positions from said navigation signals;
(c) computing orbital parameters for the satellite from said plurality of mean satellite positions; and
(d) predicting the position of the satellite at a time tn from said orbital parameters.
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Accused Products
Abstract
The position of a satellite in a satellite based navigation system is determined without reliance on satellite ephemeris data. Orbital parameters are computed for each satellite. The orbital parameters can then be used to predict the position of each satellite at any time. Subsequent ephemeris data may be compared to a predicted satellite position to determine whether the ephemeris data is corrupt. The orbital parameters may be determined by: computing a pseudorange and a velocity for a selected satellite for a plurality of times, computing at least three estimated positions of the satellite from the pseudoranges and velocities, and computing orbital parameters for the satellite from the three estimated positions. In another embodiment, the orbital parameters are determined by: determining the position of a receiver for at least three times using a constellation of satellites, using the three receiver positions to triangulate on an average position for the selected satellite in the constellation, repeating these steps until at least three mean satellite positions have been computed, computing the orbital parameters from the three mean positions of the selected satellite.
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Citations
19 Claims
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1. A method for determining the position of a satellite in a satellite based navigation system using a receiver having a known position, the method comprising the steps of:
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(a) receiving, from the satellite, a plurality of navigation signals at the receiver; (b) determining a plurality of mean satellite positions from said navigation signals; (c) computing orbital parameters for the satellite from said plurality of mean satellite positions; and (d) predicting the position of the satellite at a time tn from said orbital parameters. - View Dependent Claims (2, 3)
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4. A method for determining the position of a vehicle using navigation signals from a satellite based navigation system and a plurality of receivers having known positions, the method comprising the steps of:
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(a) receiving, at each receiver, a navigation signal from a selected satellite; (b) computing a pseudorange from said navigation signal at each receiver; (c) triangulating to determine the position of said selected satellite using said pseudoranges and the known position of each receiver; and (d) repeating steps (a)-(c) to determine a plurality of positions of said selected satellite; (e) computing orbital parameters for said selected satellite from said plurality of positions; (f) predicting the position of the satellite at a time tn from said orbital parameters; and (g) using said predicted position of said selected satellite to compute the position of the vehicle without relying on ephemeris data provided by said selected satellite. - View Dependent Claims (5)
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6. A method for determining the position of a satellite in a satellite based navigation system using a receiver having a known position, the method comprising the steps of:
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(a) receiving, from the satellite, a first navigation signal at the receiver at a time t1 ; (b) computing, from said first navigation signal, a first pseudorange and a first velocity for the satellite; (c) receiving, from the satellite, a second navigation signal at the receiver at a time t2 ; (d) computing, from said second navigation signal, a second pseudorange and a second velocity for the satellite; (e) receiving, from the satellite, a third navigation signal at the receiver at a time t3 ; (f) computing, from said third navigation signal, a third pseudorange and a third velocity for the satellite; (g) computing orbital parameters for the satellite from said pseudoranges and velocities; and (h) predicting, from said orbital parameters, the position of the satellite at a time tn. - View Dependent Claims (7)
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8. A method for determining the position of a satellite in a constellation of such satellites of a satellite based navigation system, the method comprising the steps of:
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(a) determining a first receiver position at a time t1 using the constellation of satellites; (b) determining a second receiver position at a time t2 using the constellation of satellites; (c) determining a third receiver position at a time t3 using the constellation of satellites; (d) determining a fourth receiver position at a time t4 using the constellation of satellites; (e) determining a fifth receiver position at a time t5 using the constellation of satellites; (f) selecting one of said satellites from said constellation; (g) computing a first mean satellite position for said selected satellite using data from times t1, t2, and t3 ; (h) computing a second mean satellite position for said selected satellite using data from times t2, t3, and t4 ; (i) computing a third mean satellite position for said selected satellite using data from times t3, t4, and t5 ; (j) computing a set of orbital parameters for said selected satellite using said first, second, and third mean satellite positions; and (k) predicting the position of said selected satellite at a time tn using said orbital parameters. - View Dependent Claims (9, 10, 11)
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12. An apparatus for use with a vehicle for determining the position of the vehicle relative to the center of the Earth using navigation signals from a Global Positioning System (GPS) which includes a plurality of satellites orbiting the Earth, the apparatus comprising:
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first means, having a known position, for receiving the navigation signals from the plurality of satellites and for computing a first pseudorange and a velocity for each satellite at a plurality of discrete time intervals; second means for receiving said first pseudoranges and velocities for said plurality of discrete time intervals for each satellite and for computing orbital parameters for each satellite therefrom, without relying on ephemeris data contained in said navigation signals; and third means for computing a position of the vehicle based on said orbital parameters. - View Dependent Claims (13, 14, 15)
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16. A satellite based navigation system for determining the position of a vehicle relative to the center of the Earth using navigation signals transmitted by a plurality of Earth orbiting satellites, the system comprising:
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base station means, having a known position, for receiving the navigation signals from the plurality of satellites, for computing a pseudorange and a velocity for each satellite at a plurality of discrete time intervals, and for computing orbital parameters for each satellite from said pseudoranges and velocities for said plurality of discrete time intervals, without relying on ephemeris data contained in the navigation signals; data transmitter means, coupled to said base station means, for transmitting said orbital parameters to the vehicle; data receiver means, coupled to the vehicle, for receiving said orbital parameters from said data transmitter means; and GPS receiver means, coupled to said data receiver means, for receiving the navigation signals from the plurality of satellites, for computing a pseudorange to each satellite, and for computing the position of the vehicle based on said orbital parameters and said pseudorange for each satellite.
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17. An apparatus for use with a vehicle for determining the position of the vehicle relative to the center of the Earth using navigation signals from a Global Positioning System (GPS) which includes a plurality of satellites orbiting the Earth, the apparatus comprising:
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first means, mounted on the vehicle, for receiving the navigation signals from the plurality of satellites and for computing the position of said first means based on ephemeris data and pseudoranges computed from the navigation signals; and second means for monitoring the integrity of said ephemeris data for each satellite and for determining if any of the ephemeris data is corrupt, said second means including means for determining, for each satellite, a plurality of mean satellite positions from the navigation signals, means for computing orbital parameters for each satellite from said plurality of mean satellite positions, means for predicting a position of each satellite from said orbital parameters, and means for comparing, for each satellite an ephemeris indicated satellite position to said predicted position. - View Dependent Claims (18, 19)
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Specification