Process for accurate location determination in GPS positioning system

• US 7,362,265 B2
• Filed: 04/12/2005
• Issued: 04/22/2008
• Est. Priority Date: 04/12/2005
• Status: Active Grant

• Current Assignee: Magellan Systems Japan, Inc.
• Original Assignee: Magellan Systems Japan, Inc.
• Inventors: Weill, Lawrence R.
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US11/103,499
• Publication Number:
  US 20070171124A1
• Time in Patent Office: 1,106 Days
• Field of Search: 342/357.02, 342/357.04, 342/357.05, 342/357.06, 342/357.12, 342/357.09, 701/213, 701/215
• US Class Current: 342/357.25
• CPC Class Codes: G01S 19/258 relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
• CPC Class Codes: G01S 19/42 Determining position

Abstract

A base station (server) transmits assisting information to the user'"'"'s receiver (rover). Signals from at least 5 satellites are used for 3-dimensional positioning. Pseudorange measurements are made in a system of equations having a minimum set of unknowns X,Y,Z, and T. (X,Y,Z) is the 3D rover position in a predefined coordinate system, and T is the time at which simultaneous measurements are made to determine pseudoranges to all satellites. The position of each satellite is a vector-valued function ƒ_k (T) of said time T, where f_k is determined from satellite ephemeris data or its equivalent, sent to the rover over a communication link, as well as from knowledge of the approximate position of the rover.

Claims

1. A process for accurate location determination in an assisted GPS positioning system requiring at a minimum the transmission of data corresponding to ephemeris, satellite clock correction data, and approximate position information from an information source to the rover, the process comprising:

(A1) using the signals from at least 5 satellites for 3-dimensional (3D) positioning or at least 4 satellites for 2-dimensional (2D) positioning;

(B1) using pseudorange measurements in a system of equations having, as a minimum set of unknowns for 3D positioning the unknowns X, Y, Z, and T, where (X,Y,Z) is the 3D rover position in a predefined coordinate system, and T is the time at which simultaneous measurements are made to determine pseudoranges to all satellites;

or

(C1) using pseudorange measurements in a system of equations having, as a minimum set of unknowns for 2D positioning the unknowns X, Y, and T, where (X,Y) is the 2D horizontal rover position in a predefined coordinate system, and T is the time at which simultaneous measurements are made to determine pseudoranges to all satellites;

(D1) where in said system of equations the position of each satellite is a vector-valued function ƒ

_k(T) of said time T, where ƒ

_k is determined from data corresponding to satellite ephemeris data sent to the rover over a communication link, as well as from knowledge of the approximate position of the rover,

further including a determination of accurate but ambiguous pseudorange differences by using the knowledge that the epochs of the GPS C/A pseudorandom code are transmitted at integer millisecond values of space vehicle (SV) time, which are corrected to GPS time using said satellite clock correction data.

2. The process as set forth in claim 1, in which a communication link is used for communication between the information source and the rover, and said communication link is any one, or a combination of communication means including, cellular telephone networks, wired or wireless internet access, or telephone land lines.

3. The process as set forth in claim 1, further including the resolution of ambiguity in the said pseudorange differences by using said knowledge of the approximate position of the rover, provided to the rover by the information source.

4. A process for accurate location determination in an assisted GPS positioning system requiring at a minimum the transmission of data corresponding to ephemeris, satellite clock correction data, and approximate position information from an information source to the rover, the process comprising:

(A1) using the signals from at least 5 satellites for 3-dimensional (3D) positioning or at least 4 satellites for 2-dimensional (2D) positioning;

(B1) using pseudorange measurements in a system of equations having, as a minimum set of unknowns for 3D positioning the unknowns X, Y, Z, and T, where (X,Y,Z) is the 3D rover position in a predefined coordinate system, and T is the time at which simultaneous measurements are made to determine pseudoranges to all satellites;

or

(C1) using pseudorange measurements in a system of equations having, as a minimum set of unknowns for 2D positioning the unknowns X, Y, and T, where (X,Y) is the 2D horizontal rover position in a predefined coordinate system, and T is the time at which simultaneous measurements are made to determine pseudoranges to all satellites;

(D1) where in said system of equations the position of each satellite is a vector-valued function ƒ

_k(T) of said time T, where ƒ

_k is determined from data corresponding to satellite ephemeris data sent to the rover over a communication link, as well as from knowledge of the approximate position of the rover,

further including the resolution of ambiguity in the said pseudorange differences by using said knowledge of the approximate position of the rover, provided to the rover by the information source,

wherein a least-squares interactive algorithm used for solving the solution of said system of equations starts with an initial solution estimate x=[X Y Z T]^T, and each subsequent pass through the algorithm starts with the previous solution estimate, said algorithm consisting of the following steps, the sequence of steps being repeated until convergence of the solution is obtained;

(A5) Use the data corresponding to ephemeris data received from the information source to calculate the satellite posit ions (x_k, y_k, z_k) at time T;

(B5) Compute the LOS vectors r_k and their lengths (ranges) r_k from the rover position estimate (X, Y, Z) to each satellite;

(C5) Compute the times of signal transmission t_k=T−

r_k/c for the satellites, where c is the speed of light;

(D5) Use the ephemeris data to recompute the satellite positions (x_k, y_k, z_k), the r_k and r_k, and the corresponding satellite velocity vectors v_k, using the times t_k of signal transmission for each satellite that were obtained in Step C5;

(E5) Calculate the rover-to-satellite unit vectors

5. The process as set forth in claim 4, in which the steps of said iterative algorithm are the same, except that the quantities are suitably modified for the purpose of 2D positioning.