Attitude determination using multiple baselines in a navigational positioning system

• US 6,421,003 B1
• Filed: 05/19/2000
• Issued: 07/16/2002
• Est. Priority Date: 05/19/2000
• Status: Active Grant

• Current Assignee: SRI International, Inc.
• Original Assignee: SRI International, Inc.
• Inventors: Riley, Wyatt, Gilkey, James Y.
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US09/577,036
• Time in Patent Office: 788 Days
• Field of Search: 342/357.01, 342/357.06, 342/357.11, 342/357.04, 701/213
• US Class Current: 342/357.38
• CPC Class Codes: G01S 19/54 using carrier phase measurements; using long or short baseline interferometry
• CPC Class Codes: G01S 5/0247 Determining attitude

Abstract

A method and system for performing attitude determination for an array of receivers in a navigational positioning system are described. A navigational positioning system includes an array of receiver antennas that simultaneously receive signals emitted from satellites or other fixed or moving sources. A first set of potential solutions for a first baseline vector and a second set of potential solutions for a second baseline vector determined. Each baseline vector corresponds to any pair of receiver antennas in the array. The baseline vector comprises both the scalar distance between the antennas and the orientation of the line between the antennas in a geospatial coordinate frame. In one embodiment, test results are obtained for at least two tests performed on each potential solution in a set of potential solution. Each potential solution in the sets of potential solutions is evaluated as a candidate for a correct solution for the corresponding baseline vector. The evaluation of each potential solution is based on every test result obtained for that potential solution without disqualifying any one of the potential solutions as a candidate for the correct solution based on any one test result. Comparisons between each potential solution in the first set with each potential solution in the second set determine a degree of geometric consistency between each pair of compared solutions. One of the pairs of compared potential solutions is selected as representative of the attitude of the array if the degree of consistency of that pair satisfies predetermined criteria.

Claims

1. In a positioning system having an array of satellite navigation system antennas, each antenna having a receiver, the antennas simultaneously receiving signals emitted from a plurality of signal transmitters, a method for determining an attitude of the array comprising:

determining a first set of potential solutions for a first baseline vector for any pair of antennas in the array, each of the potential solutions including an integer ambiguity value;

determining a second set of potential solutions for a second baseline vector for any other pair of antennas in the array, each of the potential solutions including an integer ambiguity value;

comparing each potential solution in the first set with each potential solution in the second set to determine a degree of geometric consistency between each pair of compared solutions;

selecting one of the pairs of compared potential solutions as representative of the attitude of the array if the corresponding pair of baseline vectors satisfies predetermined criteria.

2. The method of claim 1 further comprising the step of determining a set of potential solutions for baseline vectors of every other pair of antennas in the array.

3. The method of claim 1 further comprising the step of determining a third set of potential solutions for a third baseline vector defined by any other pair of antennas in the array when the baseline vectors of every pair of compared potential solutions fails to satisfy the predetermined criteria.

4. The method of claim 3 wherein comparing includes simultaneously comparing each potential solution in the third set with the potential solutions in the first and second sets of potential solutions.

5. The method of claim 1 wherein selecting one of the pairs of potential solutions includes determining if a degree of geometric consistency between the corresponding pair of baseline vectors satisfies the predetermined criteria.

6. The method of claim 1 further comprising:

obtaining test results for at least two tests performed on each potential solution in the first set of potential solutions; and

evaluating each potential solution in the first set as a candidate for a correct solution for the first baseline vector, wherein the evaluating of each such potential solution is based on every test result obtained for that potential solution without disqualifying any one of the potential solutions as a candidate for the correct solution for the first baseline vector based on any one test result.

7. The method of claim 1 further comprising the step of determining that the selected pair of potential solutions is the correct solution for the array attitude if the selected pair of potential solutions is the only pair of potential solutions that satisfies the predetermined criteria.

8. The method of claim 1 further comprising the steps of assigning a value to each compared pair of potential solutions, the value corresponding to a closeness of the compared pair to being a geometrically consistent solution for the attitude of the array.

9. The method of claim 8 further comprising the steps of:

determining a highest assigned value and a next highest assigned value for the compared pairs of potential solutions; and

selecting the compared pair of potential solutions with the highest assigned value as the correct solution for the attitude of the array if the highest assigned value exceeds the next highest assigned value by a predetermined margin.

10. The method of claim 1 further comprising the step of eliminating one potential solution for the first baseline vector as incorrect based on a geometric inconsistency of the first baseline vector with potential solutions of the second baseline vector in conjunction with other information.

11. The method of claim 1 further comprising the step of averaging the array attitude determined from multiple baseline vectors with correct solutions using angle offsets between receivers to improve the determined attitude of the array.

12. The method of claim 11 wherein the average is a weighted average.

13. The method of claim 1 further comprising the step of assigning a value to each pair of compared potential solutions, the assigned value corresponding to a closeness of the geometric consistency of that pair of potential solutions to providing a correct solution for the attitude of the array.

14. The method of claim 13 further comprising the steps of:

performing at least one test on each potential solution for a baseline vector;

assigning a value to each potential solution for each baseline vector based on the result of each test; and

combining the values assigned to each potential solution in a pair of compared potential solutions with the value assigned to the geometric consistency of that pair of potential solutions to produce an overall value that is used when selecting a correct solution for the attitude of the array.

18. The method of claim 1, wherein the receiver includes at least one receiver element and each antenna is in communication with one of the receiver elements.

15. In a positioning system having an array of receivers simultaneously receiving signals emitted from a plurality of signal transmitters, each pair of receivers defining a baseline vector, a method for determining an attitude of the array comprising the steps of:

selecting a set of receivers in the array that together form a closed loop;

determining a set of potential solutions for each baseline vector defined by the selected set of receivers, each of the potential solutions including an integer ambiguity value; and

selecting one of the potential solutions from each of the sets of potential solutions as a correct solution for the attitude of the array if the baseline vectors corresponding to the selected potential solutions together are geometrically consistent.

16. The method of claim 15 further comprising the step of determining that the baseline vectors of the selected potential solutions are geometrically consistent to the extent that such baseline vectors form a closed loop.

17. The method of claim 15 further comprising:

obtaining test results for at least two tests performed on each potential solution in each set of potential solutions; and

evaluating each potential solution in each set of potential solutions as a candidate for a correct solution for the corresponding baseline vector, wherein the evaluating of each such potential solution is based on every test result obtained for that potential solution without disqualifying any one of the potential solutions as a candidate based on any one test result.

19. A positioning system for determining an attitude of an array of signal receivers that simultaneously receive signals emitted from a plurality of signal transmitters, each pair of receivers in the array defining a baseline vector, the positioning system comprising:

a processor determining from the received signals a first set of potential solutions for a first baseline vector defined by any pair of receivers in the array and a second set of potential solutions for a second baseline vector for any other pair of receivers in the array, each of the potential solutions including an integer ambiguity value;

a comparator, in communication with the processor, comparing each potential solution in the first set with each potential solution in the second set to determine a degree of geometric consistency between each pair of compared solutions; and

a selector, in communication with the comparator, selecting one of the pairs of compared potential solutions as representative of the attitude of the array if the degree of consistency of that pair satisfies predetermined criteria.