Altitude estimation using a probability density function

• US 8,391,889 B2
• Filed: 06/03/2011
• Issued: 03/05/2013
• Est. Priority Date: 06/03/2011
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Marti, Lukas M., MacGougan, Glenn Donald, Mayor, Robert, Huang, Ronald K., Dere, Jason, Grosman, Yefim
• Primary Examiner(s): Hu, Jinsong
• Assistant Examiner(s): TAYLOR, NATHAN SCOTT
• Application Number:
  US13/152,606
• Publication Number:
  US 20120309408A1
• Time in Patent Office: 641 Days
• Field of Search: 4554561-4565, 455/436, 455/404.2, 342/357.43, 342/357.66
• US Class Current: 455/456.1
• CPC Class Codes: G01C 5/00 Measuring height; Measuring distances transverse to line of sight; Levelling between separated points; Surveyors' levels G01C3/20, G01C3/30 take precedence
• CPC Class Codes: G01S 5/0027 of actual mobile position, i.e. position determined on mobile
• CPC Class Codes: G01S 5/0236 Assistance data, e.g. base station almanac
• CPC Class Codes: G01S 5/0242 Determining the position of transmitters to be subsequently used in positioning G01S5/0289 takes precedence
• CPC Class Codes: G01S 5/0278 involving statistical or probabilistic considerations G01S5/0252, G01S5/0294 take precedence
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 4/023 using mutual or relative location information between multiple location based services [LBS] targets or of distance thresholds
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 64/003 locating network equipment

Abstract

Methods, program products, and systems of location estimation using a probability density function are disclosed. In general, in one aspect, a server can estimate an effective altitude of a wireless access gateway using harvested data. The server can harvest location data from multiple mobile devices. The harvested data can include a location of each mobile device and an identifier of a wireless access gateway that is located within a communication range of the mobile device. The server can calculate an effective altitude of the wireless access gateway using a probability density function of the harvested data. The probability density function can be a sufficient statistic of the received set of location coordinates for calculating an effective altitude of the wireless access gateway. The server can send the effective altitude of the wireless access gateway to other mobile devices for estimating altitudes of the other mobile devices.

Claims

1. A method performed by one or more computers, comprising:

receiving a plurality of sets of location coordinates from one or more mobile devices, each set of location coordinates being associated with a wireless access gateway;

determining an effective altitude of the wireless access gateway based on a statistical analysis of the received sets of location coordinates, wherein determining the effective altitude comprises;

mapping the sets of location coordinates to a plurality of elevation segments;

selecting one or more elevation segments from the plurality of elevation segments based on a concentration of received location coordinates in each of the elevation segments using;

a probability density function; and

a specified outlier threshold for identifying and excluding one or more outliers in the sets of location coordinates; and

determining the effective altitude using sets of location coordinates in the selected one or more elevation segments; and

providing the effective altitude to a mobile device for determining an altitude of the mobile device when the mobile device is located within a communication range of the wireless access gateway.

2. The method of claim 1, wherein each set of location coordinates includes an altitude.

3. The method of claim 1, wherein the wireless access gateway includes a wireless device operable to connect a mobile device to at least one of a personal area network, a local area network, a metropolitan area network, a wide area network, or a cellular network.

4. The method of claim 1, wherein the probability density function includes a statistic of the received sets of location coordinates for calculating the effective altitude.

5. The method of claim 1, wherein selecting the one or more elevation segments comprises:

determining, for each elevation segment and using the probability density function, an expected value based on a relative probability that a received set of location coordinates is located within the elevation segment; and

selecting the one or more elevation segments when a measurement of the expected value corresponding to the one or more elevation segments satisfies the outlier threshold.

6. The method of claim 5, wherein

each set of the location coordinates is associated with a reliability indicator, the reliability indicator including at least one of a relative signal strength indicator (RSSI), a bit error rate, or a round trip time;

and

determining the expected value includes determining the expected value based on the relative probability weighed by the associating reliability indicator.

7. The method of claim 5, comprising determining that the measurement satisfies the outlier threshold when a sum of the corresponding relative probabilities equals one minus the outlier threshold.

8. The method of claim 1, comprising:

selecting one or more sets of location coordinates from the selected one or more elevation segments based on an estimated movement of the wireless access gateway, wherein determining the effective altitude of the wireless access gateway includes determining the effective altitude of the wireless access gateway using the selected sets of location coordinates.

9. The method of claim 8, wherein selecting one or more sets of location coordinates from the selected one or more elevation segments based on the estimated movement of the wireless access gateway comprises:

determining that at least one set of location coordinates is obsolete when a variation of sets of location coordinates exceeds a threshold, indicating that the wireless access gateway has moved; and

selecting the one or more sets of location coordinates by excluding the obsolete set of location coordinates.

10. The method of claim 8, wherein:

each set of location coordinates corresponds to a time of measurement; and

selecting one or more sets of location coordinates from sets of location coordinates of the selected one or more elevation segments based on the estimated movement of the wireless access gateway comprises excluding a collection of one or more sets of location coordinates in an elevation segment when a span the corresponding time of measurements of the sets in the collection satisfies a threshold time, or, for a threshold amount of time, no update data are received.

11. A computer program product stored on a non-transitory medium and configured to cause one or more computers to perform operations comprising:

receiving a plurality of sets of location coordinates from one or more mobile devices, each set of location coordinates being associated with a wireless access gateway;

determining an effective altitude of the wireless access gateway based on a statistical analysis of the received sets of location coordinates, wherein determining the effective altitude comprises;

mapping the sets of location coordinates to a plurality of elevation segments;

selecting one or more elevation segments from the plurality of elevation segments based on a concentration of received location coordinates in each of the elevation segments using;

a probability density function; and

a specified outlier threshold for identifying and excluding one or more outliers in the sets of location coordinates; and

determining the effective altitude using sets of location coordinates in the selected one or more elevation segments; and

providing the effective altitude to a mobile device for determining an altitude of the mobile device when the mobile device is located within a communication range of the wireless access gateway.

12. The product of claim 11, wherein each set of location coordinates includes an altitude.

13. The product of claim 11, wherein the wireless access gateway includes a wireless device operable to connect a mobile device to at least one of a personal area network, a local area network, a metropolitan area network, a wide area network, or a cellular network.

14. The product of claim 11, wherein the probability density function includes a statistic of the received sets of location coordinates for calculating the effective altitude.

15. The product of claim 11, wherein selecting the one or more elevation segments comprises:

determining, for each elevation segment and using the probability density function, an expected value based on a relative probability that a received set of location coordinates is located within the elevation segment; and

selecting the one or more elevation segments when a measurement of the expected value corresponding to the one or more elevation segments satisfies the outlier threshold.

16. The product of claim 15, wherein

each set of the location coordinates is associated with a reliability indicator, the reliability indicator including at least one of a relative signal strength indicator (RSSI), a bit error rate, or a round trip time;

and

determining the expected value includes determining the expected value based on the relative probability weighed by the associating reliability indicator.

17. The product of claim 15, the operations comprising determining that the measurement satisfies the outlier threshold when a sum of the corresponding relative probabilities equals one minus the outlier threshold.

18. The product of claim 11, the operations comprising:

selecting one or more sets of location coordinates from the selected one or more elevation segments based on an estimated movement of the wireless access gateway, wherein determining the effective altitude of the wireless access gateway includes determining the effective altitude of the wireless access gateway using the selected sets of location coordinates.

19. The product of claim 18, wherein selecting one or more sets of location coordinates from the selected one or more elevation segments based on the estimated movement of the wireless access gateway comprises:

determining that at least one set of location coordinates is obsolete when a variation of sets of location coordinates exceeds a threshold, indicating that the wireless access gateway has moved; and

selecting the one or more sets of location coordinates by excluding the obsolete set of location coordinates.

20. The product of claim 18, wherein:

each set of location coordinates corresponds to a time of measurement; and

selecting one or more sets of location coordinates from sets of location coordinates of the selected one or more elevation segments based on the estimated movement of the wireless access gateway comprises excluding a collection of one or more sets of location coordinates in an elevation segment when a span the corresponding time of measurements of the sets in the collection satisfies a threshold time, or, for a threshold amount of time, no update data are received.

21. A system, comprising:

one or more computers configured to perform operations comprising;

receiving a plurality of sets of location coordinates from one or more mobile devices, each set of location coordinates being associated with a wireless access gateway;

determining an effective altitude of the wireless access gateway based on a statistical analysis of the received sets of location coordinates, wherein determining the effective altitude comprises;

mapping the sets of location coordinates to a plurality of elevation segments;

selecting one or more elevation segments from the plurality of elevation segments based on a concentration of received location coordinates in each of the elevation segments using;

a probability density function; and

a specified outlier threshold for identifying and excluding one or more outliers in the sets of location coordinates; and

determining the effective altitude using sets of location coordinates in the selected one or more elevation segments; and

providing the effective altitude to a mobile device for determining an altitude of the mobile device when the mobile device is located within a communication range of the wireless access gateway.

22. The system of claim 21, wherein each set of location coordinates includes an altitude.

23. The system of claim 21, wherein the wireless access gateway includes a wireless device operable to connect a mobile device to at least one of a personal area network, a local area network, a metropolitan area network, a wide area network, or a cellular network.

24. The system of claim 21, wherein the probability density function includes a statistic of the received sets of location coordinates for calculating the effective altitude.

25. The system of claim 21, wherein selecting the one or more elevation segments comprises:

determining, for each elevation segment and using the probability density function, an expected value based on a relative probability that a received set of location coordinates is located within the elevation segment; and

selecting the one or more elevation segments when a measurement of the expected value corresponding to the one or more elevation segments satisfies the outlier threshold.

26. The system of claim 25, wherein

each set of the location coordinates is associated with a reliability indicator, the reliability indicator including at least one of a relative signal strength indicator (RSSI), a bit error rate, or a round trip time;

and

determining the expected value includes determining the expected value based on the relative probability weighed by the associating reliability indicator.

27. The system of claim 25, the operations comprising determining that the measurement satisfies the outlier threshold when a sum of the corresponding relative probabilities equals one minus the outlier threshold.

28. The system of claim 21, the operations comprising:

selecting one or more sets of location coordinates from the selected one or more elevation segments based on an estimated movement of the wireless access gateway, wherein determining the effective altitude of the wireless access gateway includes determining the effective altitude of the wireless access gateway using the selected sets of location coordinates.

29. The system of claim 28, wherein selecting one or more sets of location coordinates from the selected one or more elevation segments based on the estimated movement of the wireless access gateway comprises:

determining that at least one set of location coordinates is obsolete when a variation of sets of location coordinates exceeds a threshold, indicating that the wireless access gateway has moved; and

selecting the one or more sets of location coordinates by excluding the obsolete set of location coordinates.

30. The system of claim 28, wherein:

each set of location coordinates corresponds to a time of measurement; and

selecting one or more sets of location coordinates from sets of location coordinates of the selected one or more elevation segments based on the estimated movement of the wireless access gateway comprises excluding a collection of one or more sets of location coordinates in an elevation segment when a span the corresponding time of measurements of the sets in the collection satisfies a threshold time, or, for a threshold amount of time, no update data are received.