ALTITUDE ESTIMATION USING A PROBABILITY DENSITY FUNCTION

• US 20130178230A1
• Filed: 03/04/2013
• Published: 07/11/2013
• 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
• Granted Patent: US 8,818,411 B2
• Time in Patent Office: Days
• 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 device;

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

mapping the sets of location coordinates to a plurality of bins, each bin including a unit area in a geographic grid;

selecting one or more bins from the plurality of bins based on a concentration of received location coordinates in each of the bins 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 location using sets of location coordinates in the selected one or more bins; and

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

2. The method of claim 1, wherein each set of location coordinates includes a latitude coordinate and a longitude coordinate.

3. The method of claim 1, wherein the wireless access device 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 location.

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

determining, for each bin 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 bin; and

selecting the one or more bins when a measurement of the expected value corresponding to the one or more bins 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 associated 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 bins based on an estimated movement of the wireless access device, wherein determining the effective location of the wireless access device includes determining the effective location of the wireless access device 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 bins based on the estimated movement of the wireless access device 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 device 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 bins based on the estimated movement of the wireless access device comprises excluding a collection of one or more sets of location coordinates in a bin 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 non-transitory storage medium storing computer instructions 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 device;

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

mapping the sets of location coordinates to a plurality of bins, each bin including a unit area in a geographic grid;

selecting one or more bins from the plurality of bins based on a concentration of received location coordinates in each of the bins 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 location using sets of location coordinates in the selected one or more bins; and

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

12. The non-transitory storage medium of claim 11, wherein each set of location coordinates includes a latitude coordinate and a longitude coordinate.

13. The non-transitory storage medium of claim 11, wherein the wireless access device 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 non-transitory storage medium of claim 11, wherein the probability density function includes a statistic of the received sets of location coordinates for calculating the effective location.

15. The non-transitory storage medium of claim 11, wherein selecting the one or more bins comprises:

determining, for each bin 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 bin; and

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

16. The non-transitory storage medium 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 associated reliability indicator.

17. The non-transitory storage medium of claim 15, 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 non-transitory storage medium of claim 11, the operations comprising:

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

19. The non-transitory storage medium of claim 18, wherein selecting one or more sets of location coordinates from the selected one or more bins based on the estimated movement of the wireless access device 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 device has moved; and

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

20. The non-transitory storage medium 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 bins based on the estimated movement of the wireless access device comprises excluding a collection of one or more sets of location coordinates in a bin 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; and

a non-transitory medium storing computer instructions configured to cause the 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 device;

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

mapping the sets of location coordinates to a plurality of bins, each bin including a unit area in a geographic grid;

selecting one or more bins from the plurality of bins based on a concentration of received location coordinates in each of the bins 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 location using sets of location coordinates in the selected one or more bins; and

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

22. The system of claim 21, wherein each set of location coordinates includes a latitude coordinate and a longitude coordinate.

23. The system of claim 21, wherein the wireless access device 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 location.

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

determining, for each bin 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 bin; and

selecting the one or more bins when a measurement of the expected value corresponding to the one or more bins 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 associated reliability indicator.

27. The system of claim 25, 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, comprising:

selecting one or more sets of location coordinates from the selected one or more bins based on an estimated movement of the wireless access device, wherein determining the effective location of the wireless access device includes determining the effective location of the wireless access device 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 bins based on the estimated movement of the wireless access device 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 device 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 bins based on the estimated movement of the wireless access device comprises excluding a collection of one or more sets of location coordinates in a bin 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.