GPS receiver with cross-track hold

• US 6,421,609 B2
• Filed: 07/12/2001
• Issued: 07/16/2002
• Est. Priority Date: 04/25/1996
• Status: Expired due to Term

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: SIRF Technology Incorporated (Qualcomm, Inc.)
• Inventors: Kohli, Sanjai
• Primary Examiner(s): ARTHUR JEANGLAUDE, GERTRUDE
• Application Number:
  US09/903,926
• Publication Number:
  US 20010047243A1
• Time in Patent Office: 369 Days
• Field of Search: 701/201, 701/205, 701/207, 701/208, 701/209, 701/213, 701/214, 701/215, 340/988, 340/990, 340/995, 342/357.01, 342/357.06, 342/357.07, 342/357.08, 342/355, 721/78.R
• US Class Current: 701/213
• CPC Class Codes: G01C 21/26 specially adapted for navigation in a road network
• CPC Class Codes: G01C 21/30 Map- or contour-matching
• CPC Class Codes: G01C 22/00 Measuring distance traversed on the ground by vehicles, persons, animals or other moving solid bodies, e.g. using odometers, using pedometers
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/34 Power consumption
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial
• CPC Class Codes: G01S 19/49 whereby the further system is an inertial position system, e.g. loosely-coupled
• CPC Class Codes: G01S 19/50 whereby the position solution is constrained to lie upon a particular curve or surface, e.g. for locomotives on railway tracks
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04B 2001/70706 using a code tracking loop, e.g. a delay locked loop
• CPC Class Codes: H04B 2201/70715 with application-specific features
• CPC Class Codes: H04B 7/216 Code division or spread-spectrum multiple access [CDMA, SSMA]

Abstract

A terrestrial C/A code GPS receiver system derives along track position information while tracking as few as two GPS satellites by use of conventional altitude hold and a cross track hold mode in which the maximum expected deviation of the vehicle from the expected track is estimated by, for example, knowledge or prediction of the width of the roadway or other track. To maintain accuracy, cross track hold is alternated with clock hold to update the cross track estimate when changes in vehicle direction are detected or when a predetermined period has elapsed.

Claims

1. A method of determining position information from GPS satellites comprising the steps of:

selecting a route to be traveled;

tracking one or more GPS satellites with a GPS receiver mounted for motion along the route; and

deriving route specific along track, cross track, altitude and satellite time information from the one or more GPS satellites being tracked.

2. A method of determining position information from GPS satellites comprising:

tracking one or more GPS satellites with a GPS receiver moving along a selected route; and

deriving route specific along track, cross track, altitude and satellite time information from the one or more GPS satellites being tracked.

3. The method of claim 2 wherein deriving route specific information further comprises estimating the route specific cross track information.

4. The method of claim 3 wherein the route specific cross track information is estimated from:

a default value related to a distance representing the expected accuracy of the GPS receiver, or

a value related to the maximum expected distance transverse to a centerline of the route to be traveled expected to be encountered during motion along the route.

5. The method of claim 2 wherein deriving route specific information further comprises operating in cross track, altitude and clock hold by estimating the route specific cross track, altitude and satellite time information.

6. The method of claim 5 wherein the route specific cross track information is estimated from:

a default value related to a distance representing the expected accuracy of the GPS receiver, or

a value related to the maximum expected distance transverse to a centerline of the route to be traveled expected to be encountered during motion along the route.

7. The method of claim 5 wherein the route specific altitude information is estimated from:

a default value related to a distance representing the expected accuracy of the GPS receiver, or

a pre-compiled database related to the route to be traveled, or

a default value related to an expected maximum altitude above sea level of the route to be traveled.

8. The method of claim 5 wherein the satellite time information is estimated from:

an internal clock previously synchronized with satellite time, or

a clock error database compiled from measurements of an internal clock compared with satellite time, or

satellite time determined from a satellite being tracked by the GPS receiver.

9. The method of claim 2 wherein deriving route specific information further comprises operating in cross track and altitude hold by estimating the route specific cross track and altitude information.

10. The method of claim 9 wherein the route specific cross track information is estimated from:

a default value related to a distance representing the expected accuracy of the GPS receiver, or

a value related to the maximum expected distance transverse to a centerline of the route to be traveled expected to be encountered during motion along the route.

11. The method of claim 9 wherein the route specific altitude information is estimated from:

a default value related to a distance representing the expected accuracy of the GPS receiver, or

a pre-compiled database related to the route to be traveled, or

a default value related to an expected maximum altitude above sea level of the route to be traveled.

12. A system for determining position information for a vehicle traveling along a selected route using GPS satellites, said system comprising:

a GPS receiver adapted for association with the vehicle and for tracking one or more GPS satellites; and

a navigation processor coupled to the receiver and adapted to estimate route-specific cross-track information to thereby operate in a cross-track hold mode and derive route-specific along-track, altitude and satellite time information from the one or more GPS satellites being tracked and the estimated route-specific cross-track information.

13. The system of claim 12 further comprising a display unit responsive to the route-specific along-track, altitude and satellite time information for providing an indication of the motion of the vehicle along the selected route.

14. The system of claim 12 wherein the route-specific cross-track information is estimated from either one of:

a default value related to the distance representing the expected accuracy of the GPS receiver; and

a value related to the maximum expected distance transverse to the centerline of the route to be traveled which is expected to be encountered during motion along the route.

15. A system for determining position information for a vehicle traveling along a selected route using GPS satellites, said system comprising:

a GPS receiver adapted for association with the vehicle and for tracking one or more GPS satellites; and

a navigation processor coupled to the receiver and adapted to estimate route-specific cross-track and altitude information to thereby operate in cross-track hold and altitude hold modes and derive route-specific along-track, altitude and satellite-time information from the one or more GPS satellites being tracked and the estimated route-specific cross-track and altitude information.

16. The system of claim 15 further comprising a display unit responsive to the route-specific along-track, altitude and satellite time information for providing an indication of the motion of the vehicle along the route.

17. The system of claim 15 wherein at least one of the route-specific cross-track hold information and altitude information is estimated from either one of:

a default value related to a distance representing the expected accuracy of the GPS receiver; and

a value related to the maximum expected distance transverse to a centerline of the route to be traveled expected to be encountered during motion along the route.

18. The system of claim 15 wherein the navigation processor periodically switches from the cross-track hold mode to a clock hold mode to derive updated cross-rack information from the one or more GPS satellites being tracked.

19. A system for determining position information for a vehicle traveling along a selected route using GPS satellites, said system comprising:

a GPS receiver adapted for association with the vehicle and for tracking one or more GPS satellites; and

a navigation processor coupled to the receiver and adapted to estimate route-specific cross-track, altitude and satellite-time information to thereby operate in cross-rack hold, altitude hold and clock hold mode and derive route-specific along-track, altitude and satellite-time information from the one or more GPS satellites being tracked and the estimated route-specific cross-track, altitude and satellite time information.

20. The system of claim 19 further comprising a display unit responsive to the route-specific along-track, altitude and satellite time information for providing an indication of the motion of the vehicle along the route.

21. The system of claim 19 wherein at least one of the route-specific cross-track hold information and altitude information is estimated from either one of:

a default value related to a distance representing the expected accuracy of the GPS receiver; and

a value related to the maximum expected distance transverse to a centerline of the route to be traveled expected to be encountered during motion along the route.