System for using differential GPS receivers with autopilot systems for category III precision approaches

• US 6,342,853 B1
• Filed: 04/15/1999
• Issued: 01/29/2002
• Est. Priority Date: 09/17/1997
• Status: Expired due to Term

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Braisted, Paul, Kalafus, Rudolph M.
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US09/293,521
• Time in Patent Office: 1,020 Days
• Field of Search: 342/357.03, 342/33, 701/215
• US Class Current: 342/357.31
• 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 2205/003 for aircraft positioning relative to the ground

Abstract

A precision approach capable dual differential global positioning system (DGPS) receiver avionics system. The system of the present invention includes a first and a second DGPS receiver. The first and second DGPS receivers are both adapted to interface with an autopilot in an aircraft. The DGPS receivers each determine the position of the aircraft as the aircraft proceeds along a flight path. Both DGPS receivers are further adapted to employ carrier aiding to smooth the code phase measurements used in determining the position of the aircraft. Within a predetermined range along the approach path of the aircraft and when the output of the first DGPS receiver and the output of the second DGPS receiver are proximate within a predetermined distance, the DGPS receivers determine a transition point. After the transition point, the DGPS receivers utilize DGPS carrier phase tracking to determine the position of the aircraft relative to its position at the transition point. The low noise characteristics of the carrier phase tracking allows the DGPS receivers to properly interface with the autopilot of the aircraft.

Claims

1. A dual differential global positioning system (DGPS) receiver avionics system, comprising:

a first DGPS receiver adapted to employ carrier aiding to smooth code-phase pseudorange measurements to determine a first position;

a second DGPS receiver adapted to employ carrier aiding to smooth code-phase pseudorange measurements to determine a second position, said first DGPS receiver and said second DGPS receiver included in an avionics system in an aircraft; and

said first DGPS receiver and said second DGPS receiver adapted to utilize carrier phase tracking such that said first position and said second position remain proximate within said predetermined distance and such that said first DGPS receiver and said second DGPS receiver generate consistent position information for said aircraft.

2. The system of claim 1 further comprising:

said first DGPS receiver and said second DGPS receiver combined into said avionics system such that said avionics system mounts in an ILS standard mounting location and uses ILS standard mounting hardware.

3. The system of claim 1 wherein said consistent position information is coupled to an autopilot of said aircraft.

4. The system of claim 3 wherein said autopilot is adapted to use said consistent position information to cause said aircraft to execute a precision approach.

5. The system of claim 3 further comprising:

said first DGPS receiver adapted to output said first position and said second DGPS receiver adapted to output said second position in an angular format consistent with ILS.

6. The system of claim 3 further comprising:

said first DGPS receiver adapted to track a first carrier phase based position measurement such that a first output to said autopilot exhibits lower noise than a first code phase based position measurement;

said second DGPS receiver adapted to track a second carrier phase based position measurement such that a second output to said autopilot exhibits lower noise than a second code phase based position measurement; and

said first output and said second output proximate within said predetermined distance.

7. The system of claim 1 further comprising:

said first DGPS receiver and said second DGPS receiver adapted to utilize a differential correction signal from a DGPS reference station.

8. The system of claim 1 further comprising:

said first DGPS receiver and said second DGPS receiver adapted to utilize signals from a wide area augmentation system satellite.

9. The system of claim 1, wherein said first DGPS receiver and said second DGPS receiver are certified to a Federal Aviation Administration Category III standard.

10. The system of claim 1, wherein said initial position is a code phase pseudo range based position.

11. The system of claim 1, wherein said initial position is coincident with said first position or said second position.

12. A differential global positioning system (DGPS) receiver avionics system, comprising:

a first DGPS receiver, said first DGPS receiver adapted to determine a first position;

a second DGPS receiver, said second DGPS receiver adapted to determine a second position, said first DGPS receiver and said second DGPS receiver coupled to an aircraft; and

said first DGPS receiver and said second DGPS receiver adapted to determine said first position and said second position utilizing code phase-based position measurements, said first DGPS receiver and said second DGPS receiver adapted to track said first position and said second position utilizing carrier phase tracking such that said first position and said second position remain proximate along a flight path of said aircraft.

13. The system of claim 12, wherein said first DGPS receiver and said second DGPS receiver are certified to a Category III standard such that an autopilot included in said aircraft can interface with said first DGPS receiver and said second DGPS receiver to execute a Category III approach.

14. The system of claim 12, further comprising:

said first DGPS receiver and said second DGPS receiver combined into a dual DGPS avionics system such that said avionics system mounts in an ILS standard mounting location and uses ILS standard mounting hardware.

15. The system of claim 12, further comprising:

said first DGPS receiver adapted to output said first position and said second DGPS receiver adapted to output said second position in an angular format configured to interface an autopilot of said aircraft.

16. The system of claim 12, further comprising:

said first DGPS receiver adapted to track a first code phase based position measurement using carrier phase tracking such that a first output to an autopilot of said aircraft exhibits lower noise than said first code phase based position measurement;

said second DGPS receiver adapted to track a second code phase based position measurement using carrier phase tracking such that a second output to said autopilot exhibits lower noise than said second code phase based position measurement; and

said first output and said second output proximate within said predetermined distance.

17. The system of claim 12, further comprising:

said first DGPS receiver and said second DGPS receiver adapted to utilize a differential correction signal from a DGPS reference station.

18. The system of claim 12, further comprising:

said first DGPS receiver and said second DGPS receiver adapted to utilize a differential correction signal from a wide area augmentation system satellite.

19. A differential global positioning system (DGPS) receiver avionics system, comprising:

a first DGPS receiver, said first DGPS receiver adapted to determine a first position;

a second DGPS receiver, said second DGPS receiver adapted to determine a second position; and

said first DGPS receiver and said second DGPS receiver adapted to determine said first position and said second position utilizing code phase-based position measurements, said first DGPS receiver and said second DGPS receiver adapted to track said first position and said second position utilizing carrier phase tracking such that said first position and said second position remain proximate over a period of time.

20. The system of claim 19 wherein said first DGPS receiver and said second DGPS receiver are combined into an avionics system in an aircraft.

21. The system of claim 20 wherein said first position and said second position are coupled to an autopilot of said aircraft.

22. The system of claim 21 wherein said autopilot is adapted to use said first position and said second position to guide said aircraft on a precision approach.

23. The system of claim 19 further comprising:

said first DGPS receiver adapted to output said first position and said second DGPS receiver adapted to output said second position in an angular format.

24. The system of claim 19 further comprising:

said first DGPS receiver adapted to track a first carrier phase based position measurement such that a first output exhibits lower noise than a first code phase based position measurement; and

said second DGPS receiver adapted to track a second carrier phase based position measurement such that a second output exhibits lower noise than a second code phase based position measurement.

25. The system of claim 19 further comprising:

said first DGPS receiver and said second DGPS receiver adapted to utilize a differential correction signal from a DGPS reference station.

26. The system of claim 19 further comprising:

said first DGPS receiver and said second DGPS receiver adapted to utilize signals from a wide area augmentation system satellite.

27. The system of claim 19, wherein said first DGPS receiver and said second DGPS receiver are certified to a Federal Aviation Administration Category III standard.

28. A method for using differential global positioning system (DGPS) receivers for providing positioning information to an aircraft, the method comprising the steps of:

a) determining a first position with a first DGPS receiver via code phase measurement;

b) determining a second position with a second DGPS receiver via code phase measurement;

c) interfacing said first DGPS receiver and said second DGPS receiver to provide steering information to an aircraft;

d) initiating an approach with said aircraft;

e) transitioning to carrier phase tracking wherein said first position is tracked via carrier phase measurement with said first DGPS receiver and said second position is tracked via carrier phase measurement with said second DGPS receiver; and

f) comparing said first position and said second position to determine whether said first position and said second position are consistent within a predetermined distance.

29. The method of claim 28, wherein step c) further comprises the steps of:

outputting said first position in an angular format consistent with ILS such that said first DGPS receiver interfaces with an autopilot of said aircraft; and

outputting said second position in angular format such that said second DGPS receiver interfaces with said autopilot.

30. The method of claim 28, wherein step e) further comprises the steps of:

determining whether said aircraft is within a predetermined range along an approach path; and

transitioning to carrier phase tracking when said aircraft is within said predetermined range.

31. A differential global positioning system (DGPS) receiver system, comprising:

a first DGPS receiver, said first DGPS receiver adapted to determine a first position;

a second DGPS receiver, said second DGPS receiver adapted to determine a second position;

said first DGPS receiver and said second DGPS receiver adapted to determine said first position and said second position utilizing code phase-based position measurements; and

said first DGPS receiver and said second DGPS receiver adapted to track said first position and said second position utilizing carrier phase tracking.

32. The system of claim 31 wherein said first DGPS receiver and said second DGPS receiver are combined into an avionics system in an aircraft.

33. The system of claim 32 wherein said first position and said second position are coupled to an autopilot of said aircraft.

34. The system of claim 33 wherein said autopilot is adapted to use said first position and said second position to guide said aircraft on a precision approach.