Method for Testing GNSS-Based Positioning Systems in Obstructed Environments

• US 20120139775A1
• Filed: 12/02/2011
• Published: 06/07/2012
• Est. Priority Date: 12/02/2010
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Popovic, Zeljko
• Granted Patent: US 9,377,535 B2
• Time in Patent Office: Days
• US Class Current: 342/173
• CPC Class Codes: G01S 19/23 Testing, monitoring, correcting or calibrating of receiver elements

Abstract

Methods of testing GNSS-based positioning systems in obstructed environments may include specifying a required accuracy threshold for use in determining a reference trajectory. One or more difficult areas of relatively poor or missing GNSS availability may be located within the obstructed environment. Positioning information may be established for first reference points outside the difficult areas. Subsequently, by surveying with respect to the first reference points, positioning information may be established for second reference points within the difficult areas. The first and second reference points may then be used to determine a true path associated with the reference trajectory. When an improved GNSS-based positioning system is navigated along the reference trajectory, a set of measured points may be gathered, and errors between the true path and a measured path (derived from the measured points) may thereby be evaluated with respect to statistical characteristics, or to other improved GNSS-based positioning systems.

Claims

1. A method for setting up a test for a GNSS-based positioning system along a reference trajectory within an obstructed environment, the method comprising steps of:

establishing positioning information for each of a plurality of first reference points outside a difficult area of the obstructed environment, a GNSS availability within the difficult area being less than a GNSS availability in a good area of the obstructed environment; and

surveying from the first reference points to establish positioning information for each of a plurality of second reference points within the difficult area, the second reference points being selected to ensure that an accuracy of the positioning information for the second reference points satisfies a required accuracy threshold for the reference trajectory.

2. The method of claim 1, wherein the selection of the second reference points includes spacing the second reference points to ensure that the required accuracy threshold is satisfied.

3. The method of claim 1, wherein the step of surveying further includes defining a first lane boundary and a second lane boundary, and the second reference points are along a lane centerline between the first lane boundary and the second lane boundary.

4. The method of claim 1, wherein at least some of the second reference points are positioned at surveyed points and at least some of the second reference points are positioned between surveyed points.

5. The method of claim 1, further comprising a step of gathering a plurality of measured points corresponding with the reference trajectory using the GNSS-based positioning system.

6. The method of claim 5, wherein a GNSS availability of a first portion of the measured points is good and a GNSS availability of a second portion of the measured points is poor.

7. The method of claim 6, wherein the GNSS availability of the first portion is characterized by having both (a) a number of visible satellites that is 5 or more, and (b) a horizontal dilution of precision that 1 or less.

8. The method of claim 6, wherein the GNSS availability of the second portion is characterized by having at least one of (a) a number of visible satellites that is 3 or less, and (b) a horizontal dilution of precision that is at 8 or more.

9. The method of claim 6, wherein a GNSS availability of a third portion of the measured points is characterized by having at least one of (a) a measured position that is missing, and (b) a distance between the reference trajectory and each point of the third portion of the measured points that exceeds a predetermined threshold amount.

10. The method of claim 9, wherein the plurality of measured points is characterized by a combined difficulty factor that is the sum of:

(a) the percentage of measured points not among the first portion, multiplied by a first scaling factor; and

(b) the percentage of measured points among either the second portion or the third portion, multiplied by a second scaling factor; and

wherein the sum of the first scaling factor and the second scaling factor is 1.

11. The method of claim 5, further comprising a step of gathering a plurality of additional measured points corresponding with the reference trajectory using an additional GNSS-based positioning system.

12. The method of claim 11, further comprising a step of determining (a) a first error data set that includes a separation between each of the second reference points and an interpolation among the plurality of measured points, and (b) a second error data set that includes a separation between each of the second reference points and an interpolation among the additional plurality of measured data points.

13. The method of claim 12, further comprising a step of selecting one of the GNSS-based positioning system and the additional GNSS-based positioning system based upon a comparison of the first error data set and the second error data set.

14. The method of claim 13, wherein a statistical characteristic of the first error data set is compared to a statistical characteristic of the second error data set.

15. The method of claim 13, wherein the GNSS availability within the difficult area is characterized by having at least one of (a) a number of visible satellites that is 3 or less, and (b) a horizontal dilution of precision that is at 8 or more, and the GNSS availability within the good area is characterized by having both (a) a number of visible satellites that is 5 or more, and (b) a horizontal dilution of precision that 1 or less.

16. The method of claim 1, further comprising steps of picking a route for the reference trajectory, and selecting a sub-set of the first reference points and a sub-set of the second-reference points corresponding with that route.

17. The method of claim 5, further comprising steps of gathering a plurality of comparison points using a comparison GNSS-based positioning system, and determining an error data set that includes a separation between each of the comparison points and one of (a) an interpolation among the plurality of measured points and (b) a corresponding point of the plurality of measured points.

18. A method for producing a reference trajectory for testing a GNSS-based positioning system in obstructed environments, the method comprising steps of:

specifying a required accuracy threshold for the reference trajectory;

locating a plurality of difficult areas within the obstructed environment, a GNSS availability within the difficult areas being less than a GNSS availability within areas outside the difficult areas, and an accuracy of GNSS-based positioning information within the difficult areas not satisfying the required accuracy threshold;

establishing positioning information for a plurality of first reference points, the first reference points being outside the difficult areas, and the positioning information for the first reference points satisfying the required accuracy threshold;

surveying to establish positioning information for a plurality of second reference points, the second reference points being inside the difficult areas, the positioning information for the second reference points being based on the positioning information for the first reference points, and a configuration of the second reference points enabling the positioning information for the second reference points to satisfy the required accuracy threshold; and

determining a plurality of true path points based upon the positioning information for at least the second reference points.

19. The method of claim 18, wherein the obstructed environment is an interconnected plurality of streets.

20. The method of claim 18, wherein the positioning information includes a longitude and a latitude.

21. The method of claim 18, wherein the configuration of the second reference points includes a spacing.

22. The method of claim 18, wherein both the first reference points and the second reference points include points along each of a first lane boundary and a second lane boundary.

23. The method of claim 22, wherein the true path points are along a lane centerline between the first lane boundary and the second lane boundary.

24. The method of claim 18, further comprising a step of gathering a plurality of measured points corresponding with the reference trajectory using the GNSS-based positioning system.

25. The method of claim 24, wherein a GNSS availability of a first portion of the measured points is good, a GNSS availability of a second portion of the measured points is poor, and a GNSS availability of a third portion of the measured points is either (a) missing or (b) indeterminate.

26. The method of claim 25, wherein the plurality of measured points is characterized by a combined difficulty factor.

27. The method of claim 18, further comprising steps of:

gathering (a) a plurality of first measured points using the GNSS-based positioning system by navigating the reference trajectory with the GNSS-based positioning system, and (b) a plurality of second measured points using an additional GNSS-based positioning system by navigating the reference trajectory with the additional GNSS-based positioning system;

interpolating (a) a first measured path from the first measured points, and (b) a second measured path from the second measured points;

determining (a) a first error data set based upon a distance from each of the true path points to the first measured path, and (b) a second error data set based upon a distance from each of the true path points to the second measured path; and

selecting one of the GNSS-based positioning system and the additional GNSS-based positioning system based upon a comparison of the first error data set to the second error data set.

28. A method for testing a GNSS-based positioning system along a reference trajectory within an obstructed environment, the method comprising steps of:

specifying a required accuracy threshold for the reference trajectory;

establishing positioning information for a plurality of first reference points within a good area of the obstructed environment, a GNSS availability within the good area being greater than a GNSS availability within a difficult area of the obstructed environment;

surveying from the first reference points to establish positioning information for a plurality of second reference points within the difficult area, a positioning of the second reference points ensuring that an accuracy of the positioning information for the second reference points satisfies the required accuracy threshold;

gathering a plurality of measured points corresponding with the reference trajectory using the GNSS-based positioning system; and

determining an error data set based upon a distance from each of the second reference points to a linear interpolation among the plurality of measured data points.

29. The method of claim 28, wherein at least some of the second reference points have positions directly determined by surveying and at least some of the second reference points have positions determined by interpolation between surveyed points.

30. The method of claim 28, further comprising a step of comparing the error data set to an additional error data set.

31. The method of claim 28, further comprising a step of evaluating the first error data set with respect to a desired statistical characteristic.