Methods and systems for mobile navigational applications using global navigation satellite systems

• US 7,436,354 B2
• Filed: 09/07/2006
• Issued: 10/14/2008
• Est. Priority Date: 09/07/2006
• Status: Active Grant

• Current Assignee: Mitre Corporation
• Original Assignee: Mitre Corporation
• Inventors: Lee, Young Chang
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US11/516,747
• Publication Number:
  US 20080062041A1
• Time in Patent Office: 768 Days
• Field of Search: 342/357.02, 342/357.06, 342/357.14, 342/357.17, 701/213, 701/215, 701/301
• US Class Current: 342/357.29
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type

Abstract

The present invention relates to providing navigation guidance for mobile users, using Global Navigation Satellite Systems (GNSSs) for applications where the user position needs to be determined in real time while meeting the navigation requirements, especially integrity requirement, for the given application. The present invention assists in providing guidance with a high availability of integrity function by trading accuracy for integrity for two different types of navigation applications. A first type of application requires a capability of detecting an occurrence of multiple satellite signal faults; the first embodiment of the invention provides this capability with a high availability of integrity, using two or more independent GNSSs. A second type of application requires a capability of detecting an occurrence of a single satellite signal fault; the second embodiment of the invention provides this capability with a high availability of integrity, using any one or a combination of GNSSs. The detecting and deriving of both methods are (i) in position domain and (ii) determinative of mobile user safety.

Claims

1. A method for facilitating vertical and horizontal guidance for mobile users using two or more independent global navigation satellite systems (GNSSs), comprising:

detecting an occurrence of one or more satellite signal faults in either one of the two independent GNSS constellations when two or more satellites become faulty simultaneously, the detecting occurring at a substantially consistent detection probability in accordance with any specified detection probability requirement; and

deriving vertical protection levels (VPLs) and horizontal protection levels (HPLs) by trading accuracy for integrity;

wherein the detecting and deriving are (i) in position domain and (ii) determinative of safety of the mobile user.

2. The method of claim 1, wherein undetected satellite signal faults create misleading information.

3. The method of claim 2, wherein the deriving is such that by trading accuracy for integrity, (i) a probability of hazardously misleading information (HMI) (Pr{HMI}) being made smaller or (ii) availability of integrity monitoring can be made higher for a given Pr{HMI} integrity requirement;

wherein availability is a percentage of time that the integrity monitoring is available, the integrity monitoring ensuring safety of the mobile user.

4. The method of claim 1, wherein the facilitating is independent of the user, type of navigation, and type of ranging signal sources.

5. The method of claim 1, wherein the HPLs and VPLs are continuously determined in real time.

6. The method of claim 1, wherein the HPLs and VPLs are derived in accordance with specified integrity requirements.

7. The method of claim 1, wherein a GNSS can be any one of (i) the Global Positioning System (GPS), (ii) the Galileo system, and (iii) the GLONASS.

8. The method of claim 1, further comprising assessing horizontal position and vertical position, wherein the assessing for horizontal position is based upon any assumed two-dimensional error distribution.

9. The method of claim 8, wherein the assessing for vertical position is based upon any assumed single-dimensional error distribution.

10. The method of claim 8, wherein the assessing includes obtaining at least three user mobile user position estimates for a given user-to-satellite geometry.

11. The method of claim 10, wherein two estimates are derived from measurements from the two independent GNSS constellations, a third estimate being a weighted average of the first two;

and

wherein the weights are chosen to minimize the protection levels and maximize the RAIM availability for vertical and horizontal positions, respectively.

12. The method of claim 11, wherein the third estimate is used for navigation, error for this estimate being bounded by the vertical and horizontal protection levels.

13. A method for facilitating mobile user navigation in which guidance is required, using a global navigation satellite system (GNSS), comprising:

detecting an occurrence of a satellite signal fault in a GNSS constellation; and

deriving protection levels by trading navigation accuracy for higher navigation integrity when determining a navigation solution;

wherein the trading includes combining two solutions with an optimized weight ratio from each pair of subset solutions.

14. The method of claim 13, wherein an undetected satellite signal fault creates misleading information.

15. The method of claim 14, wherein the deriving is such that by trading accuracy for integrity, (i) a probability of hazardously misleading information (HMI) Pr{HMI} being made smaller or (ii) availability of integrity monitoring can be made higher for a given Pr{HMI} integrity requirement;

and

wherein availability is a percentage of time that integrity monitoring capability is available, the integrity monitoring capability ensuring mobile user safety.

16. The method of claim 13, wherein the mobile user navigation in which either (i) horizontal guidance or (ii) both horizontal and vertical guidance are required.

17. The method of claim 13, wherein the protection levels are continuously determined in real time.

18. The method of claim 13, wherein the protection levels are derived in accordance with specified integrity requirements.

19. The method of claim 13, wherein a GNSS can be any one or a combination of (i) the Global Positioning System (GPS), (ii) the Galileo system, and (iii) the GLONASS.

20. The method of claim 13, further comprising assessing horizontal position and vertical position,

wherein the assessing the horizontal position is based upon any assumed single-dimensional error distribution along cross track (XTK) and along-track (ATK) axes, respectively;

and

wherein the assessing for vertical position, if vertical position is required for the application, is based on any assumed single-dimensional error distribution along the vertical axis.

21. The method of claim 13, wherein the assessing includes obtaining at least (N+1) user position estimates.

22. The method of claim 21, wherein i) first N estimates are derived, each from (N−

1) measurements out of the measurements from N satellites in view, and ii) the last (N+1)^th estimate is a weighted average of a selected pair of estimates from the first N estimates.

23. The method of claim 22, wherein a first pair of estimates is most widely separated among all pairs of estimates along a cross track (XTK) axis;

and

wherein a second pair of the estimates is the most widely separated among all pairs of estimates along an along-track (ATK) axis.

24. The method of claim 22, wherein the (N+1)^th estimate is used for navigation, an error for this estimate being bounded by protection levels minimized by the present invention.

25. The method of claim 23, wherein the deriving includes deriving cross-track and along-track protection levels for horizontal position.

26. The method of claim 25, wherein a third pair of the estimates can be determined along the vertical axis to derive VPL if vertical guidance is provided.

27. The method of claim 13, wherein the facilitating is independent of the user, type of navigation, and type of ranging signal sources.

28. The method of claim 13, wherein the detecting and deriving are (i) in position domain and (ii) determinative of mobile user safety.