Application of GPS to a railroad navigation system using two satellites and a stored database
First Claim
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1. A method of determining the location of a vehicle whose movement is constrained to a route whose location is fixed and known, comprising the steps of:
- (a) estimating the vehicle'"'"'s location along the route;
(b) receiving signals from two global position satellites;
(c) determining an angle from a vector tangent to the route at the estimated location to each of the two satellites;
(d) for each of the two satellites, determining a range error between an estimated range from the estimated location of the vehicle to the satellite and a measured range from the vehicle to the satellite;
(e) using the determined angles and determined range errors for only the two satellites, determining a distance error in the estimated location of the vehicle along the route; and
(f) combining the distance error with the estimated location to provide a determined location of the vehicle along the route.
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Abstract
A method for determining the location of a vehicle whose movement is constrained to a route whose location is fixed and known, such as a train. An initial estimate of location is made based upon information contained in a route database based on distance traveled from a reset point. The accuracy of the estimated vehicle location is improved through use of just two global positioning satellites.
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Citations
19 Claims
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1. A method of determining the location of a vehicle whose movement is constrained to a route whose location is fixed and known, comprising the steps of:
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(a) estimating the vehicle'"'"'s location along the route; (b) receiving signals from two global position satellites; (c) determining an angle from a vector tangent to the route at the estimated location to each of the two satellites; (d) for each of the two satellites, determining a range error between an estimated range from the estimated location of the vehicle to the satellite and a measured range from the vehicle to the satellite; (e) using the determined angles and determined range errors for only the two satellites, determining a distance error in the estimated location of the vehicle along the route; and (f) combining the distance error with the estimated location to provide a determined location of the vehicle along the route. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of determining the location of a vehicle which moves along a route whose location is known, and which has a positioning satellite receiver, the method comprising the steps of:
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(a) estimating a location of the vehicle using information about the known route and movement of the vehicle; (b) improving the accuracy of the estimated location by applying a correction to the estimated location derived from data received on the positioning satellite receiver from just two positioning satellites; and (c) determining an angle from a vector tangent to the route at the estimated location to each of the two satellites by computing a route unit vector that is tangent to the route at the estimated location, and computing satellite unit vectors from the estimated location to each of the two satellites, wherein the determined angles are between the route unit vector and the satellite unit vectors. - View Dependent Claims (12, 13, 14, 15)
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16. A method of determining the location of a vehicle which moves along a known route, and which has a positioning satellite receiver, the method comprising the steps of:
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(a) estimating a location of the vehicle using information about the known route and movement of the vehicle; and (b) improving the accuracy of the estimated location by applying a correction to the estimated location derived from data continuously received by the positioning satellite receiver from a plurality of positioning satellites, the step of improving including the determination of the angle from a vector tangent to the route at the estimated location to each of the satellites. - View Dependent Claims (17, 18, 19)
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Specification