System and method for generating precise position determinations

• US RE37,256 E1
• Filed: 11/05/1998
• Issued: 07/03/2001
• Est. Priority Date: 03/24/1993
• Status: Expired due to Term

• Current Assignee: Novariant Incorporated (Kubota Corporation)
• Original Assignee: Integrinautics Corporation (Kubota Corporation)
• Inventors: Powell, John D., Pervan, Boris S., Cobb, Henry S., Lawrence, David G., Cohen, Clark E., Parkinson, Bradford W.
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US09/187,194
• Time in Patent Office: 971 Days
• Field of Search: 342/357.04, 342/357.06, 342/357.11, 342/357.12, 342/357.14, 342/386
• US Class Current: 342/357.42
• CPC Class Codes: G01S 19/04 providing carrier phase data
• CPC Class Codes: G01S 19/07 providing data for correcting measured positioning data, e.g. DGPS [differential GPS] or ionosphere corrections
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/15 Aircraft landing systems
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 19/44 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method
• CPC Class Codes: G01S 19/55 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method
• CPC Class Codes: G01S 5/0009 Transmission of position information to remote stations involving assistance data G01S5/0236

Abstract

A GPS system and method for generating precise position determinations. The GPS system includes a ground based GPS reference system which receives with a reference receiver GPS signals and makes phase measurements for the carrier components of the GPS signals. The GPS reference system then generates and broadcasts an initialization signal having a carrier component and a data link signal having a data component. The data component of the data link signal contains data representing the phase measurements made by the reference receiver. The GPS system also includes a GPS mobile system which receives with a mobile position receiver the same GPS signals as were received by the reference system. In addition, the GPS position receiver receives the data link and initialization signals broadcast by the reference system. The GPS position receiver then makes phase measurements for the carrier components of the GPS signals during and after an initialization period and makes phase measurements for the initialization signal during the initialization period. In response to the phase measurements made by both the reference receiver and the position receiver during the initialization period, the position receiver generates initialization values representing resolution of the integer ambiguities of the received signals. In response to the initialization values and the phase measurements made by both the receivers after the initialization period, the position receiver generates precise position determinations to within centimeters of the exact location.

Claims

1. A method of resolving integer wavelength ambiguities associated with phase measurements made for GPS carrier signals transmitted by GPS satellites, the method being used with an aircraft on a final approach trajectory to a runway, the method comprising the steps of:

positioning one or more pseudolites each at a fixed known location with respect to a reference coordinate system in front of the runway below the final approach trajectory of the aircraft;

with the one or more pseudolites, transmitting one or more pseudolite carrier signals;

with a mobile GPS receiver system mounted on the aircraft;

receiving the transmitted one or more pseudolite carrier signals and the transmitted GPS carrier signals;

making phase measurements for the received one or more pseudolite carrier signals and the received GPS carrier signals at measurement epochs while the aircraft is on the final approach trajectory, there being an integer wavelength ambiguity associated with the phase measurements made for each of the received GPS carrier signals;

determining directions to the GPS satellites with respect to the reference coordinate system at the measurement epochs; and

resolving the integer wavelength ambiguities in response to the phase measurements, the known location of each of the one or more pseudolites, and the determined lines of sight directions to the GPS satellites.

2. The method of claim 1 wherein:

the final approach trajectory has an along track component;

the one or more pseudolites comprise two pseudolites further positioned in the positioning step on opposite sides of the along track component of the final approach trajectory.

3. The method of claim 1 wherein:

each of the one or more pseudolite carrier signals is transmitted in the pseudolite carrier signal transmitting step as a low power signal bubble;

the phase measurements are made in the phase measurement making step while the aircraft flies through the one or more low power signal bubbles on the final approach trajectory.

4. The method of claim 3 wherein each of the one or more pseudolite carrier signals is transmitted in the transmitting step with a pseudo-random code signal as an L1 C/A GPS signal.

5. The method of claim 1 wherein:

the mobile receiver system comprises a top side antenna mounted on top of the aircraft and a bottom side antenna mounted on bottom of the aircraft;

the GPS carrier signals being received in the receiving step with the top side antenna;

the one or more pseudolite carrier signals being received in the receiving step with the bottom side antenna.

6. The method claim 1 wherein:

the phase measurements are made in the phase measurement step during a period in which the aircraft flies over the one or more pseudolites on the final approach trajectory and a large angular change in geometry occurs between the mobile GPS receiver system and the one or more pseudolites;

the integer ambiguities are resolved in the resolving step with without searching through a set of potential solutions by batch processing of (A) the phase measurements, (B) the known location of each of the one or more pseudolites, and (C) the determined directions to the GPS satellites.

7. The method claim 6 wherein:

the mobile GPS receiver has undetermined positions with respect to the reference coordinate system at the measurement epochs;

the integer wavelength ambiguities are resolved with the batch processing in the resolving step based on a set of simultaneous equations that relate (A) the phase measurements, (B) the known location of each of the one or more pseudolites, (C) the determined directions to the GPS satellites, (D) the integer wavelength ambiguities, and (E) the undetermined positions of the mobile GPS receiver system, the number of the measurement epochs and the pseudolite and GPS carrier signals being such that the set of simultaneous equations is overdetermined.

8. The method of claim 7 further comprising the step of:

with the mobile GPS receiver system, computing initial guesses for the undetermined positions of the mobile GPS receiver system;

the set of simultaneous equations comprising a set of non-linear equations that are linearized so that the undetermined positions of the mobile GPS receiver system are represented as estimates and precise differences between the estimates and the undetermined positions;

the integer wavelength ambiguities being iteratively resolved with the batch processing in the resolving step by (A) resolving the integer wavelength ambiguities and computing the corrections precise differences in iterations based on the set of simultaneous equations, (B) in an initial one of the iterations, using the initial guesses as the estimates, and (C) in each subsequent one of the iterations, using as the estimates the estimates used in a directly preceding one of the iterations adjusted by the precise differences computed in the directly preceding one of the iterations.

9. A method of resolving integer wavelength ambiguities associated with phase measurements made for GPS carrier signals transmitted by GPS satellites, the method comprising the steps of:

positioning one or more pseudolites each at a fixed known location with respect to a reference coordinate system;

with the one or more pseudolites, transmitting one or more pseudolite carrier signals;

with a mobile GPS receiver system;

receiving the transmitted one or more pseudolite carrier signals and the transmitted GPS carrier signals;

making phase measurements for the received one or more pseudolite carrier signals and the received GPS carrier signals at measurement epochs while a large angular change in geometry occurs between the mobile GPS receiver system and the one or more pseudolites, there being an integer wavelength ambiguity associated with the phase measurements made for each of the received GPS carrier signals;

determining directions to the GPS satellites with respect to the reference coordinate system at the measurement epochs; and

resolving the integer wavelength ambiguities in response to the phase measurements, the known location of each of the one or more pseudolites, and the determined lines of sights directions to the GPS satellites.

10. The method claim 9 wherein the integer ambiguities are resolved in the resolving step with without searching through a set of potential solutions by batch processing of (A) the phase measurements, (B) the known location of each of the one or more pseudolites, and (C) the determined directions to the GPS satellites.

11. The method claim 10 wherein:

the mobile GPS receiver has undetermined positions with respect to the reference coordinate system at the measurement epochs;

the integer wavelength ambiguities are resolved with the batch processing in the resolving step based on a set of simultaneous equations that relate (A) the phase measurements, (B) the known location of each of the one or more pseudolites, (C) the determined directions to the GPS satellites, (D) the integer wavelength ambiguities, and (E) the undetermined positions of the mobile GPS receiver system, the number of the measurement epochs and the pseudolite and GPS carrier signals being such that the set of simultaneous equations is overdetermined.

12. The method of claim 11 further comprising the step of:

with the mobile GPS receiver system, computing initial guesses for the undetermined positions of the mobile GPS receiver system;

the set of simultaneous equations comprising a set of non-linear equations that are linearized so that the undetermined positions of the mobile GPS receiver system are represented as estimates and precise differences between the estimates and the undetermined positions;

the integer wavelength ambiguities being iteratively resolved with the batch processing in the resolving step by (A) resolving the integer wavelength ambiguities and computing the precise differences in iterations based on the set of simultaneous equations, (B) in an initial one of the iterations, using the initial guesses as the estimates, and (C) in each subsequent one of the iterations, using as the estimates the estimates used in a directly preceding one of the iterations adjusted by the precise differences computed in the directly preceding one of the iterations.

13. The method of claim 9 wherein:

the mobile GPS receiver system is mounted on an aircraft on a final approach trajectory to a runway; and

each of the one or more pseudolites is positioned in the positioning step in front of the runway below the final approach trajectory;

the phase measurements are made in the phase measurement step during a period in which the aircraft flies over the one or more pseudolites on the final approach trajectory and the large angular change in geometry occurs.

14. The method of claim 13 wherein:

the final approach trajectory has an along track component;

the one or more pseudolites comprise two pseudolites further positioned in the positioning step on opposite sides of the along track component of the final approach trajectory.

15. A method of making position determinations for a mobile GPS receiver system mounted on an aircraft on a final approach trajectory to a runway, the method comprising the steps of:

positioning one or more pseudolites each at a fixed known location with respect to a reference coordinate system in front of the runway below the final approach trajectory of the aircraft;

with the one or more pseudolites, transmitting one or more pseudolite carrier signals;

with a GPS reference system;

receiving GPS carrier signals transmitted by GPS satellites at a fixed known reference location with respect to the reference coordinate system;

transmitting reference phase information associated with the GPS carrier signals received with the GPS reference system;

with the mobile GPS receiver system;

receiving the transmitted one or more pseudolite carrier signals, the transmitted GPS carrier signals, and the transmitted reference phase information;

making phase measurements for the one or more pseudolite carrier signals and the GPS carrier signals received with the mobile GPS receiver system at measurement epochs during an initialization period while the aircraft is on the final approach trajectory and making phase measurements for the GPS carrier signals received by the mobile GPS receiver system at measurement epochs after the initialization period while the aircraft is still on the final approach trajectory, there being an integer wavelength ambiguity associated with the phase measurements made for each of the GPS carrier signals;

determining directions to the GPS satellites with respect to the reference coordinate system at the measurement epochs during and after the initialization period;

resolving the integer wavelength ambiguities in response to (A) the phase measurements made at the measurement epochs during the initialization period, (B) the known location of each of the one or more pseudolites, (C) the reference phase information received during the initialization period, and (D) the determined directions to the GPS satellites at the measurement epochs during the initialization period; and

computing positions for the mobile GPS receiver system with respect to the reference coordinate system at the measurement epochs after the initialization period in response to (A) the resolved integer ambiguities, (B) the phase measurements made at the measurement epochs after the initialization period, (C) the reference phase information received after the initialization period, and (D) the determined lines of sight directions to the GPS satellites at the measurement epochs after the initialization period.

16. The method or claim 15 wherein the reference phase information is transmitted in the reference phase information transmitting step from a fixed different location than the known location of each of the one or more pseudolites so that the transmitted reference phase information is received with the mobile GPS receiver system during and after the initialization period while the aircraft is on the final approach trajectory.

17. The method of claim 15 further comprising the step of:

with the GPS reference system, making phase measurements for the GPS carrier signals received with the GPS reference system at the measurement epochs during and after the initialization period;

the reference phase information transmitted during and after the initialization period in the reference phase information transmitting step comprising the phase measurements made during and after the initialization period with the GPS reference system.

18. The method of claim 15 wherein:

the final approach trajectory has an along track component;

the one or more pseudolites comprise two pseudolites further positioned in the positioning step on opposite sides of the along track component of the final approach trajectory.

19. The method of claim 15 wherein:

each of the one or more pseudolite carrier signals is transmitted in the pseudolite carrier signal transmitting step as a low power signal bubble;

the phase measurements made in the phase measurement making step during the initialization period are made while the aircraft flies through the low power signal bubbles on the final approach trajectory.

20. The method of claim 19 wherein each of the one or more pseudolite carrier signals is transmitted in the transmitting step with a pseudo-random code signal as an L1 C/A GPS signal.

21. The method of claim 15 wherein:

the mobile receiver system comprises a top side antenna mounted on top of the aircraft and a bottom side antenna mounted on bottom of the aircraft;

the GPS carrier signals being received with the top side antenna in the receiving step with the mobile GPS receiver system;

the one or more pseudolite carrier signals being received with the bottom side antenna in the receiving step with the mobile GPS receiver system.

22. The method of claim 15 wherein the phase measurements made in the phase measurement step during the initialization period are made while the aircraft flies over the one or more pseudolites on the final approach trajectory and a large angular change in geometry occurs between the mobile GPS receiver system and the one or more pseudolites.

23. The method of claim 22 wherein the integer ambiguities are resolved in the resolving step with without searching through a set of potential solutions by batch processing of (A) the phase measurements made at the measurement epochs during the initialization period, (B) the known location of each of the one or more pseudolites, (C) the reference phase information received during the initialization period, and (D) the determined directions to the GPS satellites at the measurement epochs during the initialization period.

24. The method claim 23 wherein:

the mobile GPS receiver has undetermined positions with respect to the reference coordinate system at the measurement epochs during the initialization period;

the integer wavelength ambiguities are resolved with the batch processing in the resolving step based on a set of simultaneous equations that relate (A) the phase measurements made at the measurement epochs during the initialization period, (B) the known location of each of the one or more pseudolites, (C) the reference phase information received during the initialization period, (D) the determined directions to the GPS satellites at the measurement epochs during the initialization, (E) the integer wavelength ambiguities, and (F) the undetermined positions of the mobile GPS receiver system at the measurement epochs during the initialization period, the number of the measurement epochs and the pseudolite and GPS carrier signals being such that the set of simultaneous equations is overdetermined.

25. The method of claim 24 further comprising the step of:

with the mobile GPS receiver system, computing initial guesses for the undetermined positions of the mobile GPS receiver system;

the set of simultaneous equations comprising a set of non-linear equations that are linearized so that the undetermined positions of the mobile GPS receiver system are represented as estimates and precise differences between the estimates and the undetermined positions;

the integer wavelength ambiguities being iteratively resolved with the batch processing in the resolving step by (A) resolving the integer wavelength ambiguities and computing the corrections precise differences in iterations based on the set of simultaneous linearized non-linear equations, (B) in an initial one of the iterations, using the initial guesses as the estimates, and (C) in each subsequent one of the iterations, using as the estimates the estimates used in a directly preceding one of the iterations adjusted by the precise differences computed in the directly preceding one of the iterations.