Method and apparatus for determining an error estimate in a hybrid position determination system

• US 6,420,999 B1
• Filed: 10/26/2000
• Issued: 07/16/2002
• Est. Priority Date: 10/26/2000
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Vayanos, Alkinoos
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/697,781
• Time in Patent Office: 628 Days
• Field of Search: 342/357.03, 342/357.02, 701/214, 701/215
• US Class Current: 342/357.31
• CPC Class Codes: G01S 19/48 by combining or switching between position solutions derived from the satellite radio beacon positioning system and position solutions derived from a further system
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0244 Accuracy or reliability of position solution or of measurements contributing thereto
• CPC Class Codes: G01S 5/0252 Radio frequency fingerprinting

Abstract

A method and apparatus that allows correlations between a selected parameter and the error in a pseudo range measurement to be exploited. A database is established in which the amount of error estimated for particular pseudo range measurements to a beacon is maintained. Clusters are defined. Each cluster is associated with a range of values for the selected parameter. Pseudo range measurements are then associated with a particular cluster based upon the value of the selected parameter at the time (or proximate to the time) the pseudo range measurement was taken. As more estimates of the pseudo range measurements are made, the size of the clusters (i.e., the range of values of the selected parameter) can be reduced. Due to the correlation between the selected parameter and the errors in the pseudo range measurements, reducing the size of the clusters reduces the variance of the error estimates. The mean value of the error estimates is used to correct the error in future pseudo range measurements.

Claims

1. A method for determining an error estimate, including the steps of:

a) determining the position of a mobile terminal using a first sub-system;

b) calculating pseudo ranges to at least one transmitter within a second sub-system using the determined position;

c) measuring pseudo ranges to the at least one transmitter within the second sub-system; and

d) comparing the calculated and measured pseudo ranges for the at least one transmitter to determine an error estimate.

2. The method of claim 1, wherein the first position determination sub-system typically determines the position of a terminal with more accuracy than the second sub-system.

8. The method of claim 1, further including the steps of:

a) determining error estimates associated with pseudo ranges to at least one transmitter from several positions;

b) defining the scope of a cluster such that variations in the error estimates that have been made by position determination terminals within the cluster are within a predetermined range.

3. A method for using an aggregate value to correct a pseudo range measurement made by a position determination sub-system, including the steps of:

a) determining a set of error estimates associated with a cluster, each error estimate within the set representing the error in a pseudo range to at least one transmitter, and each pseudo range being measured by a mobile receiver from a position within the cluster;

b) calculating an aggregate value for the set of error estimates; and

c) using the aggregate value to correct for errors in additional pseudo ranges measured within the cluster.

4. The method of claim 3, wherein the aggregate value is calculated by calculating the mean of the set of error estimates.

5. The method of claim 4, wherein the set of error estimates is weighted before calculating the mean.

6. The method of claim 5, wherein the weighting is done based upon the relative reliability of each error estimate.

7. The method of claim 3, further including the steps of:

a) associating a cluster with a range of values of a parameter; and

b) determining that an error estimate is associated with the cluster if a value of the parameter determined by a terminal to which a pseudo range associated with the error estimate is taken is within the range.

9. A method for determining an error estimate in a first sub-system using information provided by a second sub-system, including the steps of:

a) determining the position of a position determination mobile terminal using the second sub-system;

b) determining second sub-system error statistics regarding the amount of error in the determined position;

c) calculating first sub-system pseudo ranges to at least one transmitter using the determined position;

d) determining from the second sub-system error statistics, error statistics for the calculated first sub-system pseudo ranges;

e) measuring first sub-system pseudo ranges; and

f) comparing the calculated and measured first sub-system pseudo ranges to determine an error estimate.

10. The method of claim 9, wherein the first position determination sub-system typically determines the position of a terminal with more accurate than the second sub-system.

11. The method of claim 9, further including the steps of:

a) determining at least one set of error estimates from several positions within a cluster in accordance with the method recited in claim 9, each error estimate of the same set being associated with the same beacon and having been taken by a terminal within the same cluster;

b) calculating an aggregate value for at least one set of error estimates; and

c) using the aggregate value to correct for errors in subsequent measurements of pseudo ranges taken within the cluster and associated with the same beacon to which the aggregate value is associated.

12. The method of claim 11, wherein the aggregate value is calculated by calculating the mean of the set of error estimates.

13. The method of claim 12, wherein the set of error estimates is weighted before calculating the mean.

14. The method of claim 13, wherein the weighting is done based upon the relative reliability of the calculated pseudo ranges used to determine the position of the position determination terminal.

15. The method of claim 11, further including the steps of:

a) associating a cluster with a range of values of a parameter; and

b) determining that a position determination terminal is within a cluster if the value of the parameter for the position determination terminal is within the range of values associated with that cluster.

16. The method of claim 11, further including the steps of:

a) determining error estimates associated with pseudo ranges to at least one transmitter from several positions; and

b) defining the scope of a cluster such that variations in the error estimates that have been made by position determination terminals within the cluster are within a predetermined range.

17. A method for correcting errors in a pseudo range measurement, including the steps of:

a) measuring, at a mobile receiver, pseudo ranges to beacons;

b) measuring the value of a parameter;

c) determining the amount of correction to apply to the measured pseudo ranges to each beacon based upon a predetermined relationship between the value of the parameter and the correction factor to be applied; and

d) applying the determined amount of correct to each of the measured pseudo ranges.

18. A method for correcting errors in a pseudo range measurement, including the steps of:

a) measuring, at a mobile receiver, pseudo ranges to a particular beacon;

b) measuring the value of a parameter;

c) determining the amount of correction to apply to the measured pseudo ranges based upon the particular beacon, a predetermined relationship between the value of the parameter and the correction factor to be applied for the particular beacon; and

d) applying the determined amount of correct to each of the measured pseudo ranges.

19. The method of claim 18, wherein the parameter is a position of the terminal as determined from uncorrected pseudo range measurements.

20. A method for correcting errors in a pseudo range measurement, including the steps of:

a) measuring at a mobile receiver pseudo ranges to a particular beacon;

b) measuring the value of a parameter;

c) determining which cluster a terminal current resides in based upon the value of the measured parameter;

d) determining the amount of correction to apply to the measured pseudo ranges to the particular beacon based upon the cluster in which the terminal resides; and

e) applying the determined amount of correct to each of the measured pseudo ranges to the particular beacon.

21. A method for generating a sector coverage map, including the steps of:

a) determining the position of a mobile terminal using a first position determination sub-system, the first position determination sub-system being independent of the any pseudo range measurements to the beacons;

b) determining which sectors of a beacon are servicing the terminal; and

c) for each sector, creating a sector coverage map that indicates each of the positions, determined by the satellite position determination sub-system, from which a sector can provide service to a terminal.

22. The method of claim 21, further including the steps of:

a) determining the position of the terminal using a second position determination sub-system while the terminal remains at the position from which the position was determined by the first position determination sub-system; and

b) associating the location determined by the second position determination system with the location determined by the first position determination sub-system.

23. A computer readable medium encoded with a data structure for determining in which particular sector of a beacon a terminal resides, including:

a) a first list of positions associated with a particular sector, of a beacon, each such position having been determined by a first position determination sub-system, from which a terminal may be serviced by the associated sector; and

b) a second list of positions associated with the particular sector, each such position having been determined by a second position determination sub-system, from which a terminal may be serviced by a particular sector associated with the list of positions.

24. A computer readable medium encoded with a data structure for determining a correction factor to be applied to a pseudo range measurement taken by a first mobile receiver within a position determination sub-system, including:

a) a set of error estimates to be used to correct a pseudo range measurement to an associated beacon; and

b) an indication associated with the set of error estimates for identifying the associated beacon.

26. The computer readable medium of claim 24, further including an indication identifying a cluster that is associated with the aggregate error estimate.

25. A computer readable medium encoded with a data structure, for determining a correction factor to be applied to a pseudo range measurement taken by a first position determination sub-system, including:

a) an aggregate en-or estimate to be used to correct a pseudo range measurement to an associated beacon, the aggregate error estimate having been calculated from a set of error estimates, each error estimate within the set of error estimates having been calculated from the difference between a measured and a calculated pseudo range to the associated beacon; and

b) an indication associated with the aggregate error estimate for identifying the associated beacon.

27. The computer readable medium of claim 25, further including statistics for characterizing the amount of error in the error estimates.

28. The computer readable medium of claim 27, wherein the statistics include a covariance matrix.

29. The computer readable medium of claim 27, wherein the statistics include a mean of the set of error estimates.

30. The computer readable medium of claim 29, wherein the statistics include a variance of the set of error estimates.