Systems and methods of accuracy mapping in a location tracking system

• US 10,267,893 B2
• Filed: 02/22/2017
• Issued: 04/23/2019
• Est. Priority Date: 12/20/2011
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Gonia, Patrick, Kolavennu, Soumitri
• Primary Examiner(s): Faulk, Devona E
• Assistant Examiner(s): Beard, Charles L
• Application Number:
  US15/439,437
• Publication Number:
  US 20170160377A1
• Time in Patent Office: 790 Days
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0244 Accuracy or reliability of position solution or of measurements contributing thereto
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: G01S 5/145 Using a supplementary range measurement, e.g. based on pseudo-range measurements
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

Systems and method of accuracy mapping in a location tracking system are provided. Methods include identifying a position of at least one location anchor on a site rendering, determining, for a plurality of positions on the site rendering, an estimated error value of location accuracy as a function of position on the site rendering, generating an overlay rendering of the estimated error values of location accuracy for the plurality of position on the site rendering, and the site rendering with the overlay rendering therewith.

Claims

1. A method comprising:

identifying a position of each of a plurality of location anchors or a site rendering;

determining by measuring a wireless signal, for a plurality of positions on the site rendering, an upper bound and a lower bound of an estimated error value of location accuracy as a function of position on the site rendering where the upper and lower bounds of the estimated error value are respective Euclidean distances from each of at least two of the plurality of location anchors;

forming a bounding box with dimensions X and Y around each of the plurality of positions based upon intersections of the respective upper and lower bounds of the at least two location anchors, wherein forming the bounding box comprises;

creating an array of pseudo-test points, wherein the pseudo-test points are a set of points that are equidistant from two of the plurality of location anchors and are positioned to cover the site rendering entirely, thereby enabling a preparation of values of location errors for positions across a site;

calculating a received signal strength indication (RSSI) as a function of Euclidean distance from the plurality of location anchors, for each of the pseudo-test points;

calculating an expected standard deviation of RSSI; and

calculating X and Y such that the respective upper and lower bounds are based upon the standard deviation of RSSI for the pseudo-test points;

generating an overlay rendering of the estimated error values of location accuracy for the plurality of positions on the site rendering Where each estimated error value of the estimated error values is a relatively larger value of the X and Y dimensions of the bounding box of the associated position or a square root of an area of the bounding box; and

displaying the site rendering with the overlay rendering therewith.

2. The method of claim 1, wherein the overlay rendering includes a set of contours of common error values.

3. The method of claim 1, wherein identifying the position of each of the plurality of location anchors on the site rendering includes at least one of receiving coordinates of the position or receiving user input identifying the position as a position with respect to the site rendering.

4. The method of claim 3, further comprising:

receiving user input specifying a limit to the estimated error value for at least one specified area or volume in the site rendering; and

generating a set of recommended coordinates for at least one location anchor of the plurality of location anchors, wherein the estimated error value is less than the limit for all positions within the at least one specified area or volume.

5. The method of claim 4, wherein a first specified area is associated with a first limit, wherein a second specified area is associated with a second limit, wherein the first limit is different from the second limit, and wherein the set of recommended coordinates for the at least one location anchor is adjusted to ensure the estimated error value is less than the respective limit for each specified area.

6. The method of claim 5, further comprising:

providing a pre-existing set of location anchors; and

generating the set of recommended coordinates using coordinates of the pre-existing set of location anchors and adding coordinates for an additional set of location anchors to ensure the estimated error value is less than the respective limit for each specified area.

7. The method of claim 6, further comprising providing a bill of materials for the additional set of location anchors.

8. The method of claim 1, wherein identifying the position of the at least one of the plurality of location anchors on the site map includes receiving the position of the at least one location anchor as GPS coordinates.

9. The method of claim 1, wherein determining, for the plurality of positions on the site rendering, the estimated error value of location accuracy includes:

determining an upper bound limit as a function of Euclidean distance to at least one of the plurality of location anchors for each of the plurality of positions on the site rendering; and

for each of the plurality of positions on the site rendering, combining each of the upper bound limits to derive the estimated error value.

10. The method of claim 9, wherein the function of Euclidean distance is based on RSSI and wherein determining the upper bound limit and the estimated error value for each of the plurality of positions on the site map is based on determining a mean value RSSI, an expected standard deviation of RSSI, and an upper bound on the RSSI as a function of the Euclidian distance.

11. The method of claim 10, wherein determining the upper bound limit includes using the Euclidean distance to determine an expected average RSSI and using the expected average RSSI to determine the upper bound limit, wherein the upper bound limit depends on a user input specifying a desired level of confidence in location accuracy.

12. The method of claim 9, wherein the function of Euclidean distance is based on time of flight and wherein determining the upper bound limit and the estimated error value for each of the plurality of positions on the site rendering is based on determining a mean value of time of flight, an expected standard deviation of time of flight, and an upper bound of time of flight as a function of the Euclidean distance.

13. The method of claim 10, wherein the mean value of RSSI and the expected standard deviation of RSSI are based on measurements obtained in an RF site survey at a plurality of positions at the site.

14. The method of claim 10, wherein the mean value of RSSI and the expected standard deviation of RSSI are based on an RF propagation model that takes into account a presence of equipment and buildings at the site.

15. The method of claim 10, further comprising receiving user input specifying a desired level of confidence in location accuracy, and using the user input to determine the upper bound on the RSSI.

16. The method of claim 15, wherein a value of a number of RSSI standard deviations is used to determine the upper bound on the RSSI.

17. The method of claim 1, further comprising:

determining a second position of at least one location anchor of the plurality of location anchors on the site rendering based on user input;

determining, for the plurality of positions on the site rendering, a second estimated error value of location accuracy as a function of position on the site rendering;

generating a second contour map of the second estimated error value of location accuracy for the plurality of positions on the site rendering; and

displaying the second contour map.

18. The method of claim 17, further comprising:

identifying a position of a second location anchor on the site rendering;

determining, for the plurality of positions on the site rendering, a second estimated error value of location accuracy as a function of position on the site rendering;

generating a second contour map of the second estimated error value of location accuracy for the plurality of positions on the site rendering;

displaying the second contour map;

generating an inventory of contour maps; and

determining a cost before moving the at least one location anchor, a cost after moving the at least one location anchor, a cost before adding the second location anchor, and a cost after adding the second location anchor.

19. The method of claim 1, further comprising generating a bill of materials the at least one location anchor at the site.

20. The method of claim 1, wherein each of the estimated error values includes one of a worst case error value or an average error value.

21. A system comprising:

executable control software stored on a non-transitory computer readable medium; and

at least one programmable processor for;

identifying a position of a plurality of location anchors on a site rendering;

determining via a wireless signal measurement, for each of a plurality of positions on the site rendering, a respective upper bound and a lower bound of an estimated error value of location accuracy as a function of Euclidean distance from each of the plurality of location anchors;

forming a bounding box of dimensions X and Y around each of the plurality of positions based upon intersections of the respective upper and lower bounds of at least two of the plurality of location anchors, wherein forming the bounding box comprises

creating an array of pseudo-test points, wherein the pseudo-test points are a set of points that are equidistant from two of the plurality of location anchors and are positioned to cover the site rendering entirely, thereby enabling a preparation of values of location errors for positions across a site;

calculating a received signal strength indication (RSSI) as a function of Euclidean distance from the plurality of location anchors, for each of the pseudo-test points;

calculating an expected standard deviation of RSSI; and

calculating X and Y such that the respective upper and lower bounds are based upon the standard deviation of RSSI for the pseudo-test points; and

generating an overlay rendering of the estimated error values of location accuracy for the plurality of positions on the site rendering where each estimated error value of the estimated error values is a relatively larger value of the X and Y dimensions of the bounding box of the associated position or a square root of an area of the bounding box.

22. The system of claim 21, further comprising a graphical user interface for displaying the overlay rendering.

23. The system of claim 21, further comprising user inputs for adding, moving, or deleting at least one of the plurality of location anchors.

24. A method comprising:

measuring a wireless signal;

determining an upper bound and a lower bound of accuracy of a location estimate based upon the wireless signal measurement with respect to at least two different location anchors as a function of Euclidean distance for each of a plurality of locations on a site rendering;

forming a bounding box with dimensions X and Y around each of the plurality of locations by identifying intersections between the respective upper and lower bounds of the at least two different location anchors, wherein forming the bounding box comprises;

creating an array of pseudo-test points, wherein the pseudo-test points are a set of points that are equidistant from two of the plurality of location anchors and are positioned to cover the site rendering entirely, thereby enabling a preparation of values of location errors for positions across a site;

calculating a received signal strength indication (RSSI) as a function of Euclidean distance from the at least two different location anchors, for each of the pseudo-test points;

calculating an expected standard deviation of RSSI; and

calculating X and Y such that the respective upper and lower bounds are based upon the standard deviation of RSSI for the pseudo-test points;

generating an overlay rendering visually displaying the determined accuracy of the location estimate for each of the plurality of locations on the site rendering wherein the determined accuracy for each of the plurality of locations is equal to a relatively larger value of the X and Y dimensions of the bounding box of the associated location or a square root of an area of the bounding box; and

communicating the overlay rendering to a user.

25. The method of claim 24, wherein determining the accuracy of the location estimate for each of the plurality of locations on the site rendering includes determining an RSSI for each of the plurality of locations on the site rendering as a function of distance front a plurality of location anchors.