ACCOUNTING FOR ATMOSPHERIC AND TERRESTRIAL OBSTACLES IN GEOGRAPHIC POSITIONING

• US 20140266873A1
• Filed: 03/14/2013
• Published: 09/18/2014
• Est. Priority Date: 03/14/2013
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Pighin, Fred P., Klingner, Bryan, Martin, David, Filip, Daniel J., Ettinger, Scott
• Granted Patent: US 9,885,789 B2
• Time in Patent Office: Days
• US Class Current: 342/357.23
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/073 involving a network of fixed stations
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude
• CPC Class Codes: G01S 19/42 Determining position

Abstract

A position fix identifying a geographic location of a receiver is received. The position fix was generated using signals received at the receiver from respective high-altitude signal sources (such as satellites). Imagery of a geographic area that includes the geographic location is also received. The imagery is automatically processed to determine whether one or more of the high-altitude signal sources were occluded from the geographic location when the position fix was generated. In response to determining that one or more of the high-altitude signal sources were occluded from the geographic location when the position fix was generated, the position fix is identified as being potentially erroneous.

Claims

1. A method implemented in a computing system on one or more processors for identifying potentially erroneous position fixes of a receiver, the method comprising:

receiving a position fix for the receiver, wherein the position fix was generated using a plurality of signals received at the receiver from respective high-altitude signal sources, and wherein the position fix identifies a geographic location;

receiving imagery of a geographic area associated with the geographic location;

automatically processing the imagery to determine whether one or more of the high-altitude signal sources were occluded from the geographic location when the position fix was generated; and

in response to determining that one or more of the high-altitude signal sources were occluded from the geographic location when the position fix was generated, identifying the position fix as potentially erroneous.

2. The method of claim 1, further comprising:

determining a position of each of the high-altitude signal sources in a three-dimensional (3D) space, wherein the position fix specifies the geographic location as a point in a three-dimensional space;

wherein automatically processing the imagery includes identifying obstacles between the point and each of the high-altitude signal sources in the 3D space.

3. The method of claim 2, wherein identifying the obstacles includes analyzing contours of building facades.

4. The method of claim 1, wherein receiving the imagery of the geographic area includes receiving a satellite image of the geographic area.

5. The method of claim 4, wherein automatically processing the imagery includes analyzing at least one of (i) color and (ii) two-dimensional (2D) geometry to identify obstacles positioned directly above the geographic location.

6. The method of claim 5, wherein analyzing color includes identifying one or more of (i) overpasses and (ii) tree canopies.

7. The method of claim 1, wherein the received imagery was captured approximately at a time when the position fix was generated.

8. The method of claim 1, wherein automatically processing the imagery includes automatically processing the image in substantially in real time, the method further comprising:

in response to determining that one or more of the high-altitude signal sources were occluded from the geographic location when the position fix was generated, providing a notification to the receiver that the position fix is potentially erroneous.

9. The method of claim 1, wherein:

the high-altitude signal sources are satellites orbiting Earth above the atmosphere, and

the position fix is calculated using measurements of how long signals travelling from the satellites take to reach the receiver.

10. A computing system comprising:

one or more processors; and

a computer-readable medium communicatively coupled to the one or more processors and storing a plurality of instructions that, when executed on the one or more processors, cause the computing system to;

receive a position fix specifying a geographic location of a receiver, wherein the position fix was generated using a plurality of signals received at the receiver from respective signal sources disposed above a geographic area including the geographic location,

receive an obstacle map that indicates (i) first portions of the geographic area in which there is an unobstructed line of sight between an object disposed at a surface level and a signal source disposed at a level significantly higher than the surface level and (ii) second portions of the geographic area in which the line of sight between the object and the signal source is obstructed, and

using the specified geographic location and the received obstacle map, determine whether the plurality of signals reached the receiver without encountering one or more obstacles.

11. The computing system of claim 10, wherein the computer-readable medium stores further instructions that, when executed on the one or more processors, cause the computing system to generate an indicator that the position fix is erroneous in response to determining that at least one of the plurality of signals encountered an obstacle before reaching the receiver, wherein the indicator is stored in a computer-readable memory.

12. The computing system of claim 10, wherein the computer-readable medium stores further instructions that, when executed on the one or more processors, cause the computing system to:

receive a first time stamp that specifies a time when the receiver received the plurality of signals;

receive a second time stamp that specifies a time when the obstacle map was generated; and

compare the first time stamp and the second time stamp to determine whether the obstacle map can be used to determine whether the plurality of signals reached the receiver without encountering one or more obstacles.

13. The computing system of claim 10, wherein the computer-readable medium stores further instructions that, when executed on the one or more processors, cause the computing system to:

receive an image of the geographic area, captured from a satellite or an aircraft; and

automatically process the image to identify obstacles, wherein the obstacles include tree canopies.

14. A method implemented in a computing system on one or more processors for identifying line-of-sight conditions in geographic positioning, the method comprising:

receiving an image of a geographic area;

using the one or more processors, processing the image to identify obstacles that obstruct a line of sight between (i) a receiver disposed within the geographic area substantially at a surface level and (ii) a signal source disposed above the geographic area at a level significantly higher than the surface level; and

using the one or more processors, generating an obstacle map based on the identified obstacles, wherein the obstacle map indicates (i) first portions of the geographic area in which there is an unobstructed line of sight between the receiver and the signal source, and (ii) second portions of the geographic area in which the line of sight between the receiver and the signal source is obstructed.

15. The method of claim 14, further comprising:

receiving a position fix from a receiver, wherein the position fix identifies a geographic location within the geographic area;

using the obstacle map, determining whether an unobstructed line of sight to the signal source is available at the geographic location; and

in response to determining that no line of sight to the signal source is available at the geographic location, generating an indication that the position fix is potentially erroneous.

16. The method of claim 15, wherein:

receiving the position fix includes receiving a first time stamp that specifies the time at which the position fix was generated,

receiving the image of the geographic area includes receiving a second time stamp that specifies the time at which the image was captured, and

comparing the first time stamp to the second time stamp prior to determining whether the unobstructed line of sight to the signal source is available at the geographic location using the obstacle map.

17. The method of claim 14, wherein receiving the image of the geographic area includes receiving a photographic image captured from a satellite or an aircraft, and wherein processing the photographic image including identifying tree canopies.

18. The method of claim 14, wherein:

receiving the image of the geographic area includes receiving a set of panoramic photographs collected at the geographic area,

processing the image includes extracting 3D geometry from the set of panoramic photographs to identify obstacles, in a 3D space, between points in the geographic area and the signal source, and

generating the obstacle map includes using the identified obstacles.

19. The method of claim 14, further comprising:

receiving an indication of positions of a plurality of satellites at a specified time, wherein one of the plurality of satellites includes the signal source; and

using the one or more processors, processing the image to identify obstacles that obstruct a respective line of sight between the receiver and each of the plurality of satellites.

20. The method of claim 19, wherein:

in the first portions of the geographic area, there is an unobstructed line of sight between the receiver and each of the plurality of satellites, and

in the second portions of the geographic area, at least one of the lines of sight between the receiver and the plurality of satellites is obstructed.

21. A computer-based method for improved geopositioning of a receiver that receives positioning signals from a set of N signal sources, the method comprising:

(i) selecting a subset of M signal sources from among the N signal sources, wherein M<

N;

(ii) generating a candidate position fix using the positioning signals that correspond to the selected subset, wherein the candidate position fix identifies a geographic location;

(iii) using imagery of a geographic area associated with the geographic location, determining whether each of the M signal sources had an unobstructed line-of-sight to the geographic location when the position fix was generated;

(iv) if at least one of the M signal sources had an obstructed line-of-sight to the geographic location, repeating acts (i)-(iii) for a new subset of M signal sources; and

(v) generating a position fix using one or more candidate position fixes for which each of the M signal sources had an unobstructed line-of-sight to the respective geographic location.

22. The method of claim 21, wherein the subset of M signal sources corresponds to a minimum number of signal sources required to generate a positioning fix.

23. The method of claim 22, wherein the signal sources are satellites associated with Global Positioning Service (GPS).

24. The method of claim 21, wherein using the imagery of the geographic area include using a satellite photograph of an area that encompasses geographic locations corresponding to the candidate position fixes.

25. The method of claim 21, wherein using the imagery of the geographic area includes using panoramic photographs captured at a surface level.

26. The method of claim 21, wherein generating the position fix includes:

identifying a plurality of candidate position fixes for which each of the M signal sources had an unobstructed line-of-sight to the respective geographic location, and

calculating an average of the identified plurality of position fixes to generate the position fix.

27. The method of claim 21, wherein generating the position fix includes:

upon identifying a candidate position fix for which each of the M signal sources had an unobstructed line-of-sight to the corresponding geographic location, selecting the candidate position fix as the position fix.