All DOP GPS optimization

• US 5,323,163 A
• Filed: 01/26/1993
• Issued: 06/21/1994
• Est. Priority Date: 01/26/1993
• Status: Expired due to Fees

• Current Assignee: Stanley C. Maki
• Original Assignee: Stanley C. Maki
• Inventors: Maki, Stanley C.
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US08/009,093
• Time in Patent Office: 511 Days
• Field of Search: 342/357, 342/352, 342/356
• US Class Current: 342/357.48
• CPC Class Codes: G01S 19/28 Satellite selection
• CPC Class Codes: G01S 19/426 by combining or switching between position solutions or signals derived from different modes of operation in a single system

Abstract

The all DOP GPS optimization utilizes special dilution of precision (DOP) minimization measures to select the constellation of four (and fewer, with constraints) GPS satellites to form the navigation solution with optimized accuracy in the desired orthogonal component(s) of position and velocity, and the desired component of time. Furthermore, the all DOP GPS optimization utilizes multiple navigation solutions of the top ranked satellite constellations of four (and fewer) GPS satellites selected by special DOP(s) (and standard DOP(s)) minimization(s), by weighting these multiple navigation solution estimates for a component(s) of interest with the inverse of the associated DOP, and then solving for the least squares solution of these multiple navigation solution estimates. Implementation of all DOP GPS optimization is accomplished with addition of microprocessor(s), RAM memory, and ROM memory to the general processing section of a GPS receiver to implement the special DOP (and standard DOP) algorithms, the multiple parallel running navigation solutions, and the least squares solution of the the multiple navigation solution estimates by increased processing thruput, and added data, constants, and instructions storage.

Claims

1. An improved method of navigating an object using GPS (Global Positioning System) comprising:

determining the number of GPS satellites from which the object may receive radio signals;

selecting a first constellation of four GPS satellites from such number on the basis of minimizing the dilution of precision for a standard navigation solution;

using the radio signals received from such constellation to compute a standard navigation solution that minimizes the dilution of precision and which includes height, latitude, longitude, time and velocity components;

selecting at least a second constellation of four GPS satellites on the basis of minimizing the dilution of precision for a special navigation solution that includes height, latitude, longitude, time and velocity components, and

using the radio signals selected from the second constellation in which the dilution of precision is minimized for one such component to compute a special navigation solution which includes height, latitude, longitude, time and velocity components.

2. The method defined in claim 1 wherein the second constellation is selected on the basis of minimizing the Time Dilution of Precision of the special navigation solution and thereby maximize the accuracy of the height component.

3. The method defined in claim 1 wherein the second constellation is selected on the basis of minimizing the Time Dilution of Precision of the special navigation solution and thereby maximize the accuracy of the height component.

4. The method defined in claim 1 wherein the second constellation is selected on the basis of minimizing the longitude Dilution of Precision of the special navigation solution and thereby maximize the accuracy of the longitude component.

5. The method defined in claim 1 wherein the second constellation is selected on the basis of minimizing the latitude Dilution of Precision of the special navigation solution and thereby maximize the accuracy of the latitude component.

6. The method defined in claim 1 wherein the second constellation is selected on the basis of minimizing the Directional Dilution of Precision of the special navigation solution and thereby maximize the accuracy of the directional component.

7. The method defined in claim 1 wherein the second constellation is selected on the basis of minimizing the Lateral Dilution of Precision of the special navigation solution and thereby maximize the accuracy of the lateral component.

8. An improved method of navigating an object using GPS (Global Positioning System) comprising:

determining the number of GPS satellites from which the object may receive radio signals;

computing the DOP (Dilution of Precision) for a general navigation solution having position, velocity, and time components and for a special navigation solution having position, velocity and time components and in which one component of the special solution is emphasized;

ranking the computed DOP'"'"'s for all combinations of satellites according to value of DOP with the minimum value of DOP being ranked highest, and

combining the top ranked DOP'"'"'s for the top ranked satellite combinations for standard and special DOP minimization, as weighted by the inverse of an associated DDOP, in a least squares solution to provide a desired navigation solution.

9. The method of claim 8 which selects a constellation of four GPS satellites on the basis of PDOP minimization to be used for a navigation solution, to be weighted by the inverse of the associated PDOP, for a least squares solution to maximize the overall accuracy of the three position components of the navigation solution.

10. The method of claim 8 which selects a constellation of four GPS satellites on the basis of GDOP minimization to be used for a navigation solution, to be weighted by the inverse of the associated GDOP, for a least squares solution to maximized the overall accuracy of the three position components and the time component of the navigation solution.

11. The method of claim 8 which selects a constellation of four GPS satellites on the basis of HDOP minimization to be used for a navigation solution, to be weighted by the inverse of the associated HDOP, for a least squares solution to maximize the overall accuracy of the two orthogonal horizontal position components of the navigation solution.

12. The method of claim 8 which selects a constellation of four GPS satellites on the basis of TDOP minimization to be used for a navigation solution, to be weighted by the inverse of the associated TDOP, for a least squares solution to maximize the overall accuracy of the time component of the navigation solution.

13. The method of claim 8 which selects a constellation of four GPS satellites on the basis of VDOP minimization to be used for a navigation solution, to be weighted by the inverse of the associated VDOP, for a least squares solution to maximize the overall accuracy of the height component.

14. The method of claim 8 which selects a constellation of four GPS satellites on the basis of ODOP minimization to be used for a navigation solution, to be weighted by the inverse of the associated ODOP, for at least squares solution to maximize the overall accuracy of the longitude component.

15. The method of claim 8 which selects a constellation of four GPS satellites on the basis of ADOP minimization to be used for a navigation solution, to be weighted by the inverse of the associated ADOP, for a least squares solution to maximize the overall accuracy of the latitude component of the navigation solution.

16. The method of claim 8 which selects a constellation of four GPS satellites on the basis of DDOP minimization to be used for a navigation solution, to be weighted by the inverse of the associated DDOP, for a least squares solution to maximize the accuracy of the directional component along a horizontal axis rotated in azimuth from North of the navigation solution.

17. The method of claim 8 which selects a constellation of four GPS satellites on the basis of LDOP minimization to be used for a navigation solution, to be weighted by the inverse of the associated LDOP, for a least squares solution to maximize the accuracy of the lateral component along a horizontal axis perpendicular to a horizontal axis rotated in azimuth from North.

18. An improved method of navigating an object using GPS and comprising the steps of:

determining the number of GPS satellites from which the object may receive radio signals;

computing the DOP'"'"'s for all combinations of four satellites to maximize the accuracy of the position, velocity, and time components of interest of a navigation solution;

ranking all combinations of four satellites for each DOP of interest according to value with the minimum value ranked highest;

selecting the highest ranked values for each DOP of interest and the corresponding set of four GPS satellites for each DOP value;

obtaining the pseudo range and time for each of the four GPS satellites of each DOP value selected for each DOP of interest;

computing a separate Kalman filter navigation solution for each set of four satellites for each selected DOP value for each DOP of interest;

computing a least squares navigation solution for each DOP of interest from the previously computed navigation solution for selected values for the DOP of interest;

comparing the navigation solutions for each selected DOP value within each DOP of interest with the least squares navigation solution for the DOP of interest and rejecting those navigation solution from each selected DOP which have a solution difference in excess of a predetermined allowance, and

recomputing a least squares solution for each DOP of interest in the instance of rejection of a navigation solution within that DOP of interest.

19. The method of claim 18 wherein sets of only three satellites are selected in the instance where the satellites have known altitudes.