Using satellite visibility data for improved location accuracy
Described is a technology by which GPS-capable devices work with a cloud service to receive satellite visibility-related data. The satellite visibility-related data may be used to determine a location, and/or to abort a search for satellites. The cloud service may use crowd data from other GPS-capable devices. In one aspect, line-of-sight satellites are differentiated from other satellites, and used to determine which satellite signals are more trustworthy. Reflected signals also may be determined.
1. A method performed at least in part on at least one processor executing on a global positioning system (GPS)-capable device, the method comprising:
receiving, from a cloud service, satellite visibility-related data related to a predicted visibility between a plurality of satellites and the GPS-capable device;
computing a first sub-set of satellites from the plurality of satellites, the first sub-set of satellites comprising one or more satellites whose signals should be available at a given time and a given location in the absence of terrestrial structures;
computing a second sub-set of satellites from the plurality of satellites, the second sub-set of satellites comprising one or more satellites whose signals are available via line of sight at the given time and the given location;
computing a third sub-set of satellites from the plurality of satellites, the third sub-set of satellites comprising one or more satellites whose signals are available and determined to be reflected based upon line of sight at the given time and the given location;
calculating reflection angles of the signals from the third sub-set of satellites;
predicting a path of a user associated with the GPS-capable device;
applying a weighting function to the plurality of satellites, the weighting function first biasing weights ascribed to the signals received from the one or more satellites of the second sub-set of satellites and second biasing weights ascribed to the signals received from the one or more satellites of the third sub-set of satellites based on individual values of the calculated reflection angles and the predicted path;
using the biased weights and the satellite visibility-related data to determine a location of the GPS-capable device;
computing a fourth sub-set of satellites from the plurality of satellites, based upon terrestrial data and satellites that are predicted to have GPS signals detected by the GPS-capable device in the absence of obstructions, in which the fourth sub-set corresponds to one or more satellites that do not have line of sight visibility or reflected visibility to the GPS-capable device; and
aborting a search to obtain signals from a captured set of satellites responsive to the captured set of satellites matching the first sub-set of satellites with the fourth sub-set of satellites removed therefrom.
2. The method of claim 1 further comprising using the biased weight to abort a search for at least one of the plurality of satellites.
3. The method of claim 1 wherein the first sub-set of satellites is a sub-set of or equal to a full set of the plurality of satellites, and wherein the second sub-set of satellites is a sub-set of the first sub-set of satellites.
4. The method of claim 1 wherein computing the third sub-set of satellites further comprises:
using ray tracing and heuristics to determine which of the one or more satellites that are detected but are not predicted to have line-of-sight visibility are probabilistically detected to be from reflection, based upon the ray tracing and heuristics.
5. The method of claim 1 further comprising:
aborting a search to obtain signals from a captured set of satellites responsive to the captured set of satellites matching the first sub-set of satellites with the fourth sub-set of satellites removed therefrom.
6. The method of claim 1 further comprising:
determining an approximate location of the GPS-capable device in a dead zone based upon a failure by the GPS-capable device to detect a satellite signal from any satellite in the fourth sub-set.
7. The method of claim 1 further comprising:
routing a vehicle associated with the GPS-capable device around an area based upon the satellite visibility-related data.
8. The method of claim 1 , wherein the predicted visibility is based in part on one or more of the following: terrain information, ray tracing, heuristics, or signal reflection.
9. The method of claim 8 , wherein the terrain information further includes material composition of buildings.
10. The method of claim 1 , further comprising:
requesting user input corresponding to the determined location of the GPS-capable device; and
updating the determined location to improve a location estimate based at least in part on the user input received.
11. The method of claim 1 , further comprising:
determining an actual visibility between the GPS-capable device and one or more satellites of the plurality of satellites; and
updating the cloud service with other satellite visibility-related data based upon the determined actual visibility of the one or more satellites and the determined location of the GPS-capable device.
12. A global positioning system (GPS)-capable device comprising:
a memory;
at least one processor, communicatively coupled to the memory, that:
receives satellite visibility-related data related to a predicted visibility between a plurality of satellites and the GPS-capable device;
computes a first sub-set of satellites from the plurality of satellites, the first sub-set of satellites comprising one or more satellites whose signals should be available at a given time and a given location in the absence of terrestrial structures;
computes a second sub-set of satellites from the plurality of satellites, the second sub-set of satellites comprising one or more satellites whose signals are available via line of sight at the given time and the given location;
computes a third sub-set of satellites from the plurality of satellites the third sub-set of satellites comprising one or more satellites whose signals are available and determined to be reflected based upon line of sight at the given time and the given location;
calculates reflection angles of signals from the third sub-set of satellites;
predicts a path of a user associated with the GPS-capable device;
applies a weighting function to the plurality of satellites to bias weights ascribed to signals received from the second sub-set of satellites and the third sub-set of satellites, the bias towards the third sub-set of satellites based on individual values of the calculated reflection angles and the predicted path;
uses the biased weights and the received satellite visibility-related data to determine a location of the GPS-capable device;
computes a fourth sub-set of satellites from the plurality of satellites, based upon terrestrial data and satellites that are predicted to have GPS signals detected by the GPS-capable device in the absence of obstructions, in which the fourth sub-set corresponds to one or more satellites that do not have line of sight visibility or reflected visibility to the GPS-capable device; and
aborts a search to obtain signals from a captured set of satellites responsive to the captured set of satellites matching the first sub-set of satellites with the fourth sub-set of satellites removed therefrom.
13. The global positioning system (GPS)-capable device of claim 12 wherein the first sub-set of satellites is a sub-set of or equal to a full set of the plurality of satellites, and wherein the second sub-set of satellites is a sub-set of the first sub-set of satellites.
14. The global positioning system (GPS)-capable device of claim 12 wherein the processor is further configured to:
determine an approximate location of the GPS-capable device in a dead zone based upon a failure by the GPS-capable device to detect a satellite signal from any satellite in the fourth sub-set.
15. The global positioning system (GPS)-capable device of claim 12 wherein the processor is further configured to:
route a vehicle associated with the GPS-capable device around an area based upon the satellite visibility-related data.
16. The global positioning system (GPS)-capable device of claim 12 wherein the predicted visibility is based in part on one or more of the following: terrain information, ray tracing, heuristics, or signal reflection.
17. One or more computer storage devices having computer-executable instructions stored thereon, which upon execution by a computer cause the computer to perform operations comprising:
receiving, from a cloud service, satellite visibility-related data related to a predicted visibility between a plurality of satellites and the GPS-capable device;
computing a first sub-set of satellites from the plurality of satellites, the first sub-set of satellites comprising one or more satellites whose signals should be available at a given time and a given location in the absence of terrestrial structures;
computing a second sub-set of satellites from the plurality of satellites, the second sub-set of satellites comprising one or more satellites whose signals are available via line of sight at the given time and the given location;
computing a third sub-set of satellites from the plurality of satellites, the third sub-set of satellites comprising one or more satellites whose signals are available and determined to be reflected based upon line of sight at the given time and the given location;
calculating reflection angles of signals from the third sub-set of satellites;
predicting a path of a user associated with the GPS-capable device;
applying a weighting function to the plurality of satellites, the weighting function first biasing weights ascribed to signals received from the one or more satellites of the second sub-set of satellites and second biasing weights ascribed to signals received from the one or more satellites of the third sub-set of satellites based on individual values of the calculated reflection angles and the predicted path;
using the biased weights and the satellite visibility-related data to determine a location of the GPS-capable device;
computing a fourth sub-set of satellites from the plurality of satellites, based upon terrestrial data and satellites that are predicted to have GPS signals detected by the GPS-capable device in the absence of obstructions, in which the fourth sub-set corresponds to one or more satellites that do not have line of sight visibility or reflected visibility to the GPS-capable device; and
aborting a search to obtain signals from a captured set of satellites responsive to the captured set of satellites matching the first sub-set of satellites with the fourth sub-set of satellites removed therefrom.
18. The one or more computer storage devices of claim 17 having further computer-executable instructions comprising:
using ray tracing and heuristics to determine which of the one or more satellites that are detected but are not predicted to have line-of-sight visibility are probabilistically detected to be from reflection, based upon the ray tracing and heuristics.
19. The one or more computer storage devices of claim 17 having further computer-executable instructions comprising:
determining an approximate location of the GPS-capable device in a dead zone based upon a failure by the GPS-capable device to detect a satellite signal from any satellite in the fourth sub-set.
20. The one or more computer storage devices of claim 17 having further computer-executable instructions comprising:
routing a vehicle associated with the GPS-capable device around an area based upon the satellite visibility-related data.