Mitigating effects of multipath during position computation

• US 9,720,071 B2
• Filed: 10/14/2015
• Issued: 08/01/2017
• Est. Priority Date: 10/20/2014
• Status: Active Grant

• Current Assignee: NextNav, LLC
• Original Assignee: NextNav, LLC
• Inventors: Sendonaris, Andrew, Raghupathy, Arun
• Primary Examiner(s): Ngo, Chuong A
• Application Number:
  US14/882,652
• Publication Number:
  US 20160109556A1
• Time in Patent Office: 657 Days
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/428 using multipath or indirect path propagation signals in position determination
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/0273 using multipath or indirect path propagation signals in position determination
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308

Abstract

Estimating an unknown position of a receiver. In some embodiment, trilateration techniques that quantify uncertainty in the estimate of the unknown position are applied. One such technique for estimating a two-dimensional or three-dimensional position of a receiver uses an L-1 norm computation instead of an L-2 norm computation.

Claims

1. A computer-implemented method for determining how to estimate one or more positions of a receiver, wherein the method comprises:

determining whether to estimate a first latitude and a first longitude of a first position of the receiver using a first objective function that calculates an L-1 norm of residuals or a second objective function that calculates an L-2 norm of residuals,

wherein the determination is based on one or more of;

—

(1) data specifying a geographical region in which the receiver is located, (2) data specifying whether the receiver is indoors or outdoors, or (3) data specifying whether a signal received by the receiver from a transmitter meets a predefined multipath condition.

2. The method of claim 1, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude based on a cell ID, one or more satellite signals, or one or more local area network signals; and

after determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the first objective function.

3. The method of claim 1, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying the geographical region in which the receiver is located;

determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude when the data specifying the geographical region in which the receiver is located indicates that the receiver is located in a first type of environment of at least two types of environments; and

after determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the first objective function.

4. The method of claim 1, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying the geographical region in which the receiver is located;

determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude when the data specifying the geographical region in which the receiver is located indicates that the geographical region includes more than a predefined number of buildings with heights that exceed a threshold height; and

after determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the first objective function.

5. The method of claim 1, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying whether the receiver is indoors or outdoors;

determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude when the data specifying whether the receiver is indoors or outdoors indicates that the receiver is indoors; and

after determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the first objective function.

6. The method of claim 1, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying whether the signal received by the receiver from the transmitter meets the predefined multipath condition;

determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude when the data specifying whether the signal received by the receiver meets the predefined multipath condition indicates that the signal meets the predefined multipath condition; and

after determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the first objective function.

7. The method of claim 1, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying whether the signal received by the receiver from the transmitter meets the predefined multipath condition;

determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude when the data specifying whether the signal received by the receiver meets the predefined multipath condition indicates that a pseudorange measurements corresponding to the signals includes a multipath error that exceeds a threshold amount of error; and

after determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the first objective function.

8. The method of claim 1, wherein the method further comprises:

estimating a second latitude and a second longitude of a second position of the receiver using the first objective function;

estimating the second latitude and the second longitude using the second objective function;

using a sensor of the receiver to estimate movement of the receiver to the second position from a previously occupied position of the receiver;

selecting, based on the estimated movement, either the estimates of the second latitude and the second longitude resulting from the first objective function, or the estimates of the second latitude and second first longitude resulting from the second objective function; and

using the selected estimates to generate an estimate of the second position of the receiver.

9. The method of claim 1, wherein the method further comprises:

estimating a second latitude and a second longitude of a second position of the receiver using the first objective function;

estimating the second latitude and the second longitude using the second objective function;

using a sensor of the receiver to estimate movement of the receiver to the second position from a previously occupied position of the receiver;

estimating the second latitude and the second longitude using the estimated movement in addition to estimated latitude and longitude coordinates of the previously occupied position;

selecting between the estimates of the second latitude and the second longitude resulting from the first objective function and the estimates of the second latitude and the second longitude resulting from the second objective function based on a first comparison between the estimates of the second latitude and the second longitude resulting from the first objective function and the estimates of the second latitude and the second longitude that were estimated using the estimated movement of the receiver in addition to the estimated latitude and the longitude coordinates of the previously occupied position, and further based on a second comparison between the estimates of the second latitude and the second longitude resulting from the second objective function and the estimates of the second latitude and the second longitude that were estimated using the estimated movement of the receiver in addition to the estimated latitude and the longitude coordinates of the previously occupied position; and

using the selected estimates to generate an estimate of the second position of the receiver.

10. The method of claim 1, wherein the method further comprises:

determining the first objective function by inserting a first time bias function that includes a weighted median into an objective function; and

determining the second objective function by inserting a second time bias function that includes a weighted mean into the objective function.

11. The method of claim 1, wherein the method further comprises:

computing an estimate of a first altitude corresponding to the first position of the receiver using a pressure value measured by a sensor of the receiver, wherein the first latitude and the first longitude are estimated by inputting the estimate of the first altitude into the first objective function or into the second objective function.

12. The method of claim 1, wherein the method further comprises:

determining a global minimum from among two or more local minimums of the first objective function using a global optimization function that is based on a differential evolution approach for determining the global minimum.

13. The method of claim 1, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying the geographical region in which the receiver is located;

determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude when the data specifying the geographical region in which the receiver is located indicates that the receiver is not located in a first type of environment of at least two types of environments; and

after determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the second objective function.

14. The method of claim 1, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying the geographical region in which the receiver is located;

determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude when the data specifying the geographical region in which the receiver is located indicates that the geographical region includes no more than a predefined number of buildings with heights that exceed a threshold height; and

after determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the second objective function.

15. The method of claim 1, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying whether the receiver is indoors or outdoors;

determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude when the data specifying whether the receiver is indoors or outdoors indicates that the receiver is outdoors; and

after determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the second objective function.

16. The method of claim 1, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying whether the signal received by the receiver from the transmitter meets the predefined multipath condition;

determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude when the data specifying whether the signal received by the receiver meets the predefined multipath condition indicates that the signal does not meet the predefined multipath condition; and

after determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the second objective function.

17. The method of claim 1, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying whether the signal received by the receiver from the transmitter meets the predefined multipath condition;

determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude when the data specifying whether the signal received by the receiver meets the predefined multipath condition indicates that a pseudorange measurement corresponding to the signal does not include a multipath error that exceeds a threshold amount of error; and

after determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the second objective function.

18. One or more non-transitory machine-readable media embodying program instructions that, when executed by one or more machines, cause the one or more machines to implement a method for determining how to estimate one or more positions of a receiver, wherein the method comprises:

determining whether to estimate a first latitude and a first longitude of a first position of the receiver using a first objective function that calculates an L-1 norm of residuals or a second objective function that calculates an L-2 norm of residuals,

wherein the determination is based on one or more of;

(1) data specifying a geographical region in which the receiver is located, (2) data specifying whether the receiver is indoors or outdoors, or (3) data specifying whether a signal received by the receiver from a transmitter meets a predefined multipath condition.

19. The one or more non-transitory machine-readable media of claim 18, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude based on a cell ID, one or more satellite signals, or one or more local area network signals; and

after determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the first objective function.

20. The one or more non-transitory machine-readable media of claim 18, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying the geographical region in which the receiver is located;

determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude when the data specifying the geographical region in which the receiver is located indicates that the receiver is located in a first type of environment of at least two types of environments; and

after determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the first objective function.

21. The one or more non-transitory machine-readable media of claim 18, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying the geographical region in which the receiver is located;

determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude when the data specifying the geographical region in which the receiver is located indicates that the geographical region includes more than a predefined number of buildings with heights that exceed a threshold height; and

after determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the first objective function.

22. The one or more non-transitory machine-readable media of claim 18, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying whether the receiver is indoors or outdoors;

determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude when the data specifying whether the receiver is indoors or outdoors indicates that the receiver is indoors; and

after determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the first objective function.

23. The one or more non-transitory machine-readable media of claim 18, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying whether the signal received by the receiver from the transmitter meets the predefined multipath condition;

determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude when the data specifying whether the signal received by the receiver meets the predefined multipath condition indicates that the signal meets the predefined multipath condition; and

after determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the first objective function.

24. The one or more non-transitory machine-readable media of claim 18, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying whether the signal received by the receiver from the transmitter meets the predefined multipath condition;

determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude when the data specifying whether the signal received by the receiver meets the predefined multipath condition indicates that a pseudorange measurement corresponding to the signal includes a multipath error that exceeds a threshold amount of error; and

after determining to use the first objective function instead of the second objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the first objective function.

25. The one or more non-transitory machine-readable media of claim 18, wherein the method further comprises:

estimating a second latitude and a second longitude of a second position of the receiver using the first objective function;

estimating the second latitude and the second longitude using the second objective function;

using a sensor of the receiver to estimate movement of the receiver to the second position from a previously occupied position of the receiver;

selecting, based on the estimated movement, either the estimates of the second latitude and the second longitude resulting from the first objective function, or the estimates of the second latitude and second first longitude resulting from the second objective function; and

using the selected estimates to generate an estimate of the second position of the receiver.

26. The one or more non-transitory machine-readable media of claim 18, wherein the method further comprises:

estimating a second latitude and a second longitude of a second position of the receiver using the first objective function;

estimating the second latitude and the second longitude using the second objective function;

using a sensor of the receiver to estimate movement of the receiver to the second position from a previously occupied position of the receiver;

estimating the second latitude and the second longitude using the estimated movement in addition to estimated latitude and longitude coordinates of the previously occupied position;

selecting between the estimates of the second latitude and the second longitude resulting from the first objective function and the estimates of the second latitude and the second longitude resulting from the second objective function based on a first comparison between the estimates of the second latitude and the second longitude resulting from the first objective function and the estimates of the second latitude and the second longitude that were estimated using the estimated movement of the receiver in addition to the estimated latitude and the longitude coordinates of the previously occupied position, and further based on a second comparison between the estimates of the second latitude and the second longitude resulting from the second objective function and the estimates of the second latitude and the second longitude that were estimated using the estimated movement of the receiver in addition to the estimated latitude and the longitude coordinates of the previously occupied position; and

using the selected estimates to generate an estimate of the second position of the receiver.

27. The one or more non-transitory machine-readable media of claim 18, wherein the method further comprises:

determining the first objective function by inserting a first time bias function that includes a weighted median into an objective function; and

determining the second objective function by inserting a second time bias function that includes a weighted mean into the objective function.

28. The one or more non-transitory machine-readable media of claim 18, wherein the method further comprises:

computing an estimate of a first altitude corresponding to the first position of the receiver using a pressure value measured by a sensor of the receiver, wherein the first latitude and the first longitude are estimated by inputting the estimate of the first altitude into the first objective function or into the second objective function.

29. The one or more non-transitory machine-readable media of claim 18, wherein the method further comprises:

determining a global minimum from among two or more local minimums of the first objective function using a global optimization function that is based on a differential evolution approach for determining the global minimum.

30. The one or more non-transitory machine-readable media of claim 18, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying the geographical region in which the receiver is located;

determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude when the data specifying the geographical region in which the receiver is located indicates that the receiver is not located in a first type of environment of at least two types of environments; and

after determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the second objective function.

31. The one or more non-transitory machine-readable media of claim 18, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying the geographical region in which the receiver is located;

determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude when the data specifying the geographical region in which the receiver is located indicates that the geographical region includes no more than a predefined number of buildings with heights that exceed a threshold height; and

after determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the second objective function.

32. The one or more non-transitory machine-readable media of claim 18, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying whether the receiver is indoors or outdoors;

determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude when data specifying whether the receiver is indoors or outdoors indicates that the receiver is outdoors; and

after determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the second objective function.

33. The one or more non-transitory machine-readable media of claim 18, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying whether the signal received by the receiver from the transmitter meets the predefined multipath condition;

determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude when the data specifying whether the signal received by the receiver meets the predefined multipath condition indicates that the signal does not meet the predefined multipath condition; and

after determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the second objective function.

34. The one or more non-transitory machine-readable media of claim 18, wherein determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on the data specifying whether the signal received by the receiver from the transmitter meets the predefined multipath condition;

determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude when the data specifying whether the signal received by the receiver meets the predefined multipath condition indicates that a pseudorange measurement corresponding to the signal does not include a multipath error that exceeds a threshold amount of error; and

after determining to use the second objective function instead of the first objective function to estimate the first latitude and the first longitude, estimating the first latitude and the first longitude using the second objective function.