Position location of multiple transponding platforms and users using two-way ranging as a calibration reference for GPS

• US 20030208317A1
• Filed: 04/24/2001
• Published: 11/06/2003
• Est. Priority Date: 12/10/1998
• Status: Active Grant

• Current Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Original Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Inventors: Cheng, David C,, Chang, Donald C.D., Chang, Ming U., Yung, Kar W., Hagen, Frank A.
• Granted Patent: US 6,785,553 B2
• Time in Patent Office: Days
• US Class Current: 701/213
• 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 19/15 Aircraft landing systems
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04B 7/18504 Aircraft used as relay or high altitude atmospheric platform
• CPC Class Codes: H04B 7/18532 Arrangements for managing transmission, i.e. for transporting data or a signalling message
• CPC Class Codes: H04B 7/18534 for enhancing link reliablility, e.g. satellites diversity

Abstract

A method and system for using two-way ranging navigation to accurately determine the location of a transponder platform above-Earth or a fixed or mobile target on the ground or on water. The two-way ranging navigation measurements are used as calibration references, thereby improving the positioning accuracy of GPS. The system includes GPS and a two-way ranging navigation system for taking position measurements of a target. A correction factor is determined as a function of the measurements and the GPS position is adjusted by the correction factor. The method for calibrating GPS using two-way ranging navigation involves taking a two-way ranging navigation measurement and a GPS measurement of a target, determining a correction factor as a function of the measurements, and correcting the GPS position by taking a second GPS measurement and adjusting it by the correction factor.

Claims

1. A method for locating the position of a transponding platform using a global positioning system and a two-way ranging navigation system, said method comprising the steps of:

taking a two-way ranging navigation measurement of said the transponding platform at a first predetermined time;

taking a first global positioning system measurement of said transponding platform at said first predetermined time;

determining a correction factor as a function of said two-way ranging navigation measurement and said global positioning system measurement; and

obtaining a corrected global positioning measurement by taking a second global positioning system measurement of said transponding platform at a second predetermined time and adjusting said second global positioning system measurement by said correction factor.

2. The method of claim 1 wherein said step of determining a correction factor further comprises determining said correction factor as function of said two-way ranging navigation measurement and said global positioning system measurement at said first predetermined time and a known transponding platform position.

3. The method of claim 1 wherein said step of determining a correction factor further comprises determining said correction factor as a function of said two-way ranging navigation measurement at said first predetermined time and data from an inertial navigation system located on-board said transponding platform.

4. The method of claim 1 wherein said step of determining a correction factor further comprises determining said correction factor as a function of said two-way ranging navigation measurement, said global positioning system measurement at said first predetermined time and results of Extended Kalman Filtering.

5. The method of claim 1 wherein said step of correcting the global positioning system position further comprises relaying data and measurements by way of two-way communication links.

6. The method of claim 1 wherein said step of determining a correction factor further comprises performing data processing at a ground station.

7. The method of claim 1 wherein said step of determining a correction factor further comprises translating said correction factor into GPS range correction factors.

8. The method of claim 1 further comprising the step of repeating the calibration method steps when weather conditions change.

9. The method of claim 1 further comprising the step of enhancing the accuracy of said calibrating method by increasing the frequency of two-way ranging and navigation measurements.

10. The method of claim 1 further comprising the steps of:

sending said correction factor to a ground station; and

broadcasting said correction factor throughout a predetermined region.

11. The method of claim 1 wherein said two-way ranging navigation system is a back-up navigation method for said global positioning system in instances of failure of said global positioning system.

12. A method for locating the position of a target, comprising the steps of:

a) taking a first global positioning system measurement of the target at a first predetermined period of time;

b) taking a two way ranging navigation measurement of the target at said first predetermined period of time, said two way ranging navigation system comprising;

i) at least one ground station;

ii) a plurality of transponding platforms in communication with said ground station through a first link; and

iii) a target in communication with said transponding platforms through a second link, said first and second links defining a path for carrying transmissions including a unique coded signal wherein each said path is a two way communication network between one of said plurality of transponding platforms, said ground station and said target, said communication network includes ranging determination for said target with respect to at least two of said paths including a transmission with said unique coded signal portion;

c) determining a correction factor as a function of said two-way ranging navigation measurement and said global positioning system measurement; and

d) obtaining a corrected global positioning system measurement by taking a second global positioning system measurement of said target at a second predetermined time and adjusting said second global positioning system measurement by said correction factor.

13. The method of claim 12, wherein once a corrected global positioning system measurement is obtained, subsequent two way ranging navigation measurements of the target at subsequent predetermined periods of time to calculate and apply GPS correction factors are repeated at intermittent time intervals.

14. The method of claim 13, wherein the intermittent time interval is reduced for greater positioning accuracy and increased for lesser positioning accuracy.