Accounting for atmospheric and terrestrial obstacles in geographic positioning

1. 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 including obstacle specified imagery of the geographic area, the obstacle specified imagery being transitory imagery or persistent imagery, the obstacle map indicating (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.

2. The computing system of claim 1 , 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.

3. The computing system of claim 1 , 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 plurality of time stamps that specifies a time when the receiver received each of the plurality of signals;

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

compare the first plurality of time stamps 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.

4. The computing system of claim 1 , 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.

5. The computing system of claim 4 , 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.

6. The computing system of claim 5 , wherein metadata is included with the panoramic photographs.

7. The computing system of claim 1 , wherein the signal sources are satellites associated with Global Positioning Service (GPS).

8. A method, comprising:

receiving, by one or more processors, 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;

receiving, by the one or more processors, an obstacle map that including obstacle specified imagery of the geographic area, the obstacle specified imagery being transitory imagery or persistent imagery, the obstacle map indicating (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

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

9. The method of claim 8 , further comprising generating, by the one or more processors, 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.

10. The method of claim 8 , further comprising:

receiving, by the one or more processors, a first plurality of time stamps that specifies a time when the receiver received each of the plurality of signals;

receiving, by the one or more processors, a second time stamp that specifies a time when the obstacle map was generated; and

comparing, using the one or more processors, the first plurality of time stamps 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.

11. The method of claim 8 , further comprising:

receiving, by the one or more processors, an image of the geographic area, captured from a satellite or an aircraft; and

automatically processing, by the one or more processors, the image to identify obstacles, wherein the obstacles include tree canopies.

12. The method of claim 11 , 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.

13. The method of claim 12 , wherein metadata is included with the panoramic photographs.

14. The method of claim 8 , wherein the signal sources are satellites associated with Global Positioning Service (GPS).

15. A non-transitory computer readable storage medium storing instructions executable by a processor for performing a method comprising:

receiving 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;

receiving an obstacle map that including obstacle specified imagery of the geographic area, the obstacle specified imagery being transitory imagery or persistent imagery, the obstacle map indicating (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

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

16. The non-transitory computer readable storage medium of claim 15 , further comprising generating 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.

17. The non-transitory computer readable storage medium of claim 15 , further comprising:

receiving a first plurality of time stamps that specifies a time when the receiver received each of the plurality of signals;

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

comparing the first plurality of time stamps 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.

18. The non-transitory computer readable storage medium of claim 15 , further comprising:

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

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

19. The non-transitory computer readable storage medium of claim 18 , 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.

20. The non-transitory computer readable storage medium of claim 8 , wherein the signal sources are satellites associated with Global Positioning Service (GPS).