System and method for improving GPS accuracy in a device by utilizing increased time stamp accuracy

• US 9,261,599 B1
• Filed: 12/27/2012
• Issued: 02/16/2016
• Est. Priority Date: 09/17/2012
• Status: Expired due to Fees

• Current Assignee: WolfGIS, LLC
• Original Assignee: Wolf-Tek LLC
• Inventors: Golden, John Michael, Macgreigor, U. Angus
• Primary Examiner(s): Phan, Dao
• Application Number:
  US13/728,919
• Time in Patent Office: 1,146 Days
• Field of Search: 342/357.21, 342/357.25, 342/357.4, 342/357.64, 701/468, 701/469
• US Class Current: 1/1
• CPC Class Codes: G01S 19/23 Testing, monitoring, correcting or calibrating of receiver elements
• CPC Class Codes: G01S 19/256 relating to timing, e.g. time of week, code phase, timing offset

Abstract

A system and method is disclosed for updating the universal time within a GPS enable device in real-time and utilizing that corrected time to improve upon pseudorange calculations in the GPS devices. A time shim is introduced to correct outlier time values and provide improved pseudorange calculations to the device operating system, as well as draw upon various predictive smoothing methods of timestamp and position data to improve GPS location values. The improved GPS data is then provided to a location services process running on the device in an expected format and timing such that the operating system is unaware that the prior application interface of the system has been circumvented.

Claims

1. A method for improving GPS calculations in a GPS enabled device, comprising the steps of:

a. introducing a shim to circumvent an existing programming interface between a pseudo-range equation processing module and a location services module in a GPS enabled device;

b. obtaining a NIST certified time value and comparing that value to existing time values to be used by said pseudo-range equation processing module in making pseudo-range calculations;

c. utilizing said NIST certified time value in pseudo-range equation processing when said NIST certified time value is more accurate than the existing time value being utilized thereby improving pseudo-range calculation results;

d. transferring said improved pseudo-range calculation results to a location services module in said device; and

,

e. utilizing said shim to spoof a GPS enabled device operating system into utilizing said improved pseudo-range calculation results as if they were produced with original time values.

2. A method as recited in claim 1, further including the step of making outlier modifications to pseudo-range equation enhancement sub-processing.

3. A method as recited in claim 2, wherein said pseudo-range equation enhancement sub-processing comprises making differential corrections whereby reverse GPS calculations from a base station having a known GPS location in communication with said GPS enabled device are utilized to make outlier modifications to pseudo-range equation enhancement processing.

4. A method as recited in claim 2, wherein said pseudo-range equation enhancement sub-processing comprises carrier phase tracking to enhance satellite signal synchronization.

5. A method as recited in claim 2, wherein said pseudo-range equation enhancement sub-processing comprises receiver autonomous integrity monitoring.

6. A method as recited in claim 2, wherein said pseudo-range equation enhancement sub-processing comprises atmospheric correction.

7. A method as recited in claim 1, wherein said step of obtaining a NIST certified time value and comparing that value to existing time values to be used by said pseudo-range equation processing module in making pseudo-range calculations comprises the steps of

a. loading local time held by said GPS enabled device into memory;

b. accessing a NIST time source and loading that NIST time value into memory;

c. comparing the local time value to the NIST time source;

d. If said NIST time source is more accurate than said local time value then load it into time stamp memory location; and

,

e. If said NIST time source is less than or equal to said local time value, then save said local time value into time stamp memory repeat said comparison steps a-c at least 50 times.

8. A method as recited in claim 7, wherein said step of accessing a NIST time source comprises accessing a certified NIST time server.

9. A method as recited in claim 1, wherein said step of utilizing said NIST certified time value in pseudo-range equation processing when said NIST certified time value is more accurate than the existing time value being utilized comprises the steps of:

a. utilizing said NIST certified time value to calculate the pseudo-range and rate;

b. calculating a phase shift;

c. repeating steps a-b at least 50 times per minute;

d. recording a rolling 3 minute history of said step c;

e. smoothing 50 carrier phase readings; and

f. comparing said 50 smoothed carrier phase carrier phase readings to at least 4 satellite calculations.

10. A method as recited in claim 9, further including the steps of:

a. smoothing data from received from local GPS messages and NIST certified time value in pseudo-range equation processing;

b. calculating a variance on said smoothed data;

c. determining whether said variance exceeds a preselected value;

d. if said variance does not exceed said preselected value then transfer said smoothed data to said location services module; and

,

e. if said variance exceeds said preselected value then repeat steps a-c at least 50 times per minute.

11. A method as recited in claim 1, wherein said step of utilizing said NIST certified time value in pseudo-range equation processing when said NIST certified time value is more accurate than the existing time value being utilized comprises the steps of:

a. receiving a 50 cycle GPS value data set;

b. assigning a bias number to each received cycle;

c. smoothing said bias number in step b;

d. calculating multi-path errors for each 50 value data set;

e. excluding any outliers found in said 50 value data set;

f. storing in memory data remaining after said exclusion step e; and

,

g. identifying said multi-path errors and notifying a user.

12. A method for improving GPS calculations in a GPS enabled device, comprising the steps of:

a. introducing a shim to circumvent an existing programming interface between a pseudo-range equation processing module and a location services module in a GPS enabled device;

b. obtaining a NIST certified time value and comparing that value to existing time values to be used by pseudo-range equation enhancement sub-processing;

c. utilizing said NIST certified time value in said pseudo-range equation enhancement sub-processing when said NIST certified time value is more accurate than the existing time value being utilized thereby improving said pseudo-range equation enhancement sub-processing;

d. utilizing results in said step of using NIST certified time values in said pseudo-range equation enhancement sub-processing in said pseudo-range equation processing module to improve pseudo-range equation accuracy;

e. transferring improved pseudo-range calculation results to a location services module in said device; and

,

f. utilizing said shim to spoof a GPS enable device operating system into utilizing said improved pseudo-range calculation results as if they were produced with original time values.

13. A method as recited in claim 12, wherein said pseudo-range equation enhancement sub-processing comprises processing sub-modules selected from the group consisting of differential corrections whereby reverse GPS calculations from a base station having a known GPS location are in communication with said GPS enabled device are utilized to make outlier modifications to pseudo-range equation enhancement processing, carrier phase tracking to enhance satellite signal synchronization, receiver autonomous integrity monitoring, DOP orbital error signal exclusion, and atmospheric correction of GPS messages.

14. A method as recited in claim 12, wherein said step of utilizing said NIST certified time value in pseudo-range equation processing when said NIST certified time value is more accurate than the existing time value being utilized comprises the steps of:

a. utilizing said NIST certified time value to calculate the pseudo-range and rate;

b. calculating a phase shift;

c. repeating steps a-b at least 50 times per minute;

d. recording a rolling 3 minute history of said step c;

e. smoothing 50 carrier phase readings; and

f. comparing said smoothed 50 phase carrier phase readings to at least 4 satellite calculations.

15. A method as recited in claim 12, further including the steps of:

a. smoothing data from received from local GPS messages and NIST certified time value in pseudo-range equation processing;

b. calculating a variance on said smoothed data;

c. determining whether said variance exceeds a preselected value;

d. if said variance does not exceed said preselected value then transfer said smoothed data to said location services module; and

,

e. if said variance exceeds said preselected value then repeat steps a-c at least 50 times per minute.

16. A method as recited in claim 12, wherein said step of utilizing said NIST certified time value in pseudo-range equation processing when said NIST certified time value is more accurate than the existing time value being utilized comprises the steps of:

a. receiving a 50 cycle GPS value data set;

b. assigning a bias number to each received cycle;

c. smoothing said bias number in step b;

d. calculating multi-path errors for each 50 value data set;

e. excluding any outliers found in said 50 value data set;

f. storing in memory data remaining after said exclusion step e; and

,

g. identifying said multi-path errors and notifying a user.

17. A system for improving GPS calculations in a GPS enabled device, comprising:

a. means for introducing a shim to circumvent an existing programming interface between a pseudo-range equation processing module and a location services module in a GPS enabled device;

b. means for obtaining a NIST certified time value and comparing that value to existing time values to be used by pseudo-range equation enhancement sub-processing;

c. means for utilizing said NIST certified time value in said pseudo-range equation enhancement sub-processing when said NIST certified time value is more accurate than the existing time value being utilized thereby improving said pseudo-range equation enhancement sub-processing;

d. means for utilizing results in said step of using NIST certified time values in said pseudo-range equation enhancement sub-processing in said pseudo-range equation processing module to improve pseudo-range equation accuracy;

e. means for transferring said improved pseudo-range calculation results to a location services module in said device; and

,

f. means for utilizing said shim to spoof the GPS enable device operating system into utilizing said improved pseudo-range calculation results as if they were produced with the original time values.

18. A system as recited in claim 17, wherein said pseudo-range equation enhancement sub-processing comprises means for processing sub-modules selected from the group consisting of means for differential corrections whereby reverse GPS calculations from a base station having a known GPS location are in communication with said GPS enabled device are utilized to make outlier modifications to pseudo-range equation enhancement processing, means for carrier phase tracking to enhance satellite signal synchronization, means for receiver autonomous integrity monitoring, and means for atmospheric correction of GPS messages.

19. A system as recited in claim 17, wherein said means for utilizing said NIST certified time value in pseudo-range equation processing when said NIST certified time value is more accurate than the existing time value being utilized comprises:

a. means for utilizing said NIST certified time value to calculate the pseudo-range and rate;

b. means for calculating a phase shift;

c. means for recording a rolling 3 minute data history from said means for utilizing said NIST certified time value to calculate the pseudo-range and rate;

d. means for smoothing 50 carrier phase readings; and

e. means for comparing said smoothing means results to at least 4 satellite calculations.

20. A system as recited in claim 17, further including:

a. means for smoothing data from received from local GPS messages and NIST certified time value in pseudo-range equation processing;

b. means for calculating a variance on said smoothed data;

c. means for determining whether said variance exceeds a preselected value;

d. means for determining if said variance does not exceed said preselected value and transferring said smoothed data to said location services module; and

,

e. means for if said variance exceeds said preselected value then repeating processing in said smoothing means and said variance calculating means at least 50 times per minute.

21. A system as recited in claim 17, wherein said means for utilizing said NIST certified time value in pseudo-range equation processing when said NIST certified time value is more accurate than the existing time value being utilized comprises:

a. means for receiving a 50 cycle GPS value data set;

i. means for assigning a bias number to said means for receiving a 50 cycle GPS value data set;

ii. means for smoothing said bias numbers formed in said bias means;

iii. means for calculating multi-path errors for each 50 value data set;

iv. means for excluding any outliers found in said 50 value data set;

v. means for storing in memory data remaining from said excluding means; and

,

vi. means for identifying said multi-path errors and notifying a user.