Method of estimating the error in the calculation of the position of a mobile by a GPS receiver, and GPS receiver for implementing this method
First Claim
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1. A method of determining the spatial and temporal position of a global positioning system (GPS) receiver carried by a mobile in a GPS system including a plurality of GPS satellites, said method comprising the steps of:
- receiving signals from at least four said GPS satellites selected by said receiver to form a calculation constellation;
processing the received signals to determine the spatial and temporal position of the GPS receiver in a predetermined frame of reference in which x, y and z are respectively the abscissa, ordinate and third coordinate of said position, and t is the date in universal time at which said receiver is at the position (x, y, z); and
estimating an error between the determined position and an actual position of said receiver, said estimating step comprising the steps ofrepresenting the error by a vector ε
whose components are respectively the estimated error on the abscissa dx, the estimated error on the ordinate dy, the estimated error on the third coordinate dz and the estimated time error c.dt where c is the speed of light in vacuum,effecting said estimate by said GPS receiver for each calculated position, e being given by the equation
space="preserve" listing-type="equation">ε
.sub.r =K.ε
where;
K is a matrix with N rows and four columns, and N is the number of satellites in said constellation such that ##EQU6## aij varying from 1 through N and j varying from 1 through 3 being the direction cosine of the angle between the jth coordinate axis and the straight line segment joining said mobile to the ith satellite of said constellation, the subscripts 1, 2 and 3 being respectively associated with the abscissa, ordinate and third coordinate axes,ε
r is a vector with N components URE1 through UREN where UREi for i varying from 1 through N is a datum, supplied by said ith satellite, giving the mean radial error between the theoretical position of said ith satellite and its actual position on the straight line segment joining said ith satellite to a point in a geographical area on the Earth as seen by said ith satellite; and
calculating the mean at the points of said geographical area at which a GPS ground station is located.
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Abstract
In a method of calculation by a GPS receiver of the position of a mobile in space and time relative to a predetermined frame of reference, the position is calculated from data supplied by at least four GPS satellites selected by the GPS receiver to form a calculation constellation. The method includes the step of estimating the error in the position calculation. This error is estimated by the GPS receiver for each calculated position. The estimated error therefore varies with the position of the mobile.
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14 Claims
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1. A method of determining the spatial and temporal position of a global positioning system (GPS) receiver carried by a mobile in a GPS system including a plurality of GPS satellites, said method comprising the steps of:
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receiving signals from at least four said GPS satellites selected by said receiver to form a calculation constellation; processing the received signals to determine the spatial and temporal position of the GPS receiver in a predetermined frame of reference in which x, y and z are respectively the abscissa, ordinate and third coordinate of said position, and t is the date in universal time at which said receiver is at the position (x, y, z); and estimating an error between the determined position and an actual position of said receiver, said estimating step comprising the steps of representing the error by a vector ε
whose components are respectively the estimated error on the abscissa dx, the estimated error on the ordinate dy, the estimated error on the third coordinate dz and the estimated time error c.dt where c is the speed of light in vacuum,effecting said estimate by said GPS receiver for each calculated position, e being given by the equation
space="preserve" listing-type="equation">ε
.sub.r =K.εwhere; K is a matrix with N rows and four columns, and N is the number of satellites in said constellation such that ##EQU6## aij varying from 1 through N and j varying from 1 through 3 being the direction cosine of the angle between the jth coordinate axis and the straight line segment joining said mobile to the ith satellite of said constellation, the subscripts 1, 2 and 3 being respectively associated with the abscissa, ordinate and third coordinate axes, ε
r is a vector with N components URE1 through UREN where UREi for i varying from 1 through N is a datum, supplied by said ith satellite, giving the mean radial error between the theoretical position of said ith satellite and its actual position on the straight line segment joining said ith satellite to a point in a geographical area on the Earth as seen by said ith satellite; andcalculating the mean at the points of said geographical area at which a GPS ground station is located. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A GPS receiver adapted to implement a method of determining the spatial and temporal position of a global positioning system (GPS) receiver carried by a mobile in a GPS system including a plurality of GPS satellites, said method comprising the steps of:
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receiving signals from at least four said GPS satellites selected by said receiver to form a calculation constellation; processing the received signals to determine the spatial and temporal position of the GPS receiver in a predetermined frame of reference in which x, y and z are respectively the abscissa, ordinate and third coordinate of said position, and t is the date in universal time at which said receiver is at the position (x, y, z); and estimating an error between the determined position and an actual position of said receiver, said estimating step comprising the steps of representing the error by a vector ε
whose components are respectively the estimated error on the abscissa dx, the estimated error on the ordinate dy, the estimated error on the third coordinate dz and the estimated time error c.dt where c is the speed of light in vacuum,effecting said estimate by said GPS receiver for each calculated position, ε
being given by the equation
space="preserve" listing-type="equation">ε
.sub.r =K.εwhere; K is a matrix with N rows and four columns, and N is the number of satellites in said constellation such that ##EQU9## aij for i varying from 1 through N and j varying from 1 through 3 being the direction cosine of the angle between the jth coordinate axis and the straight line segment joining said mobile to the ith satellite of said constellation, the subscripts 1, 2 and 3 being respectively associated with the abscissa, ordinate and third coordinate axes, ε
r is a vector with N components URE1 through UREN where UREi for i varying from 1 through N is a datum, supplied by said ith satellite, giving the mean radial error between the theoretical position of said ith satellite and its actual position on the straight line segment joining said ith satellite to a point in a geographical area on the Earth as seen by said ith satellite; andcalculating the mean at the points of said geographical area at which a GPS ground station is located. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification