Systems and methods for determining heading

• US 8,346,466 B2
• Filed: 11/11/2009
• Issued: 01/01/2013
• Est. Priority Date: 11/11/2009
• Status: Active Grant

• Current Assignee: Northrop Grumman Guidance & Electronics Co., Inc. (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Guidance & Electronics Co., Inc. (Northrop Grumman Corporation)
• Inventors: Ahmadi, Reza, Chueh, Kainan, Dickman, T Jeffrey
• Primary Examiner(s): Tarcza, Thomas
• Assistant Examiner(s): ALHARBI, ADAM MOHAMED
• Application Number:
  US12/616,487
• Publication Number:
  US 20110112767A1
• Time in Patent Office: 1,147 Days
• Field of Search: None
• US Class Current: 701/216
• CPC Class Codes: G01C 21/005 with correlation of navigation data from several sources, e.g. map or contour matching G01C21/30 takes precedence
• CPC Class Codes: G01C 21/12 executed aboard the object being navigated; Dead reckoning
• CPC Class Codes: G01C 21/1656 with passive imaging devices, e.g. cameras
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/30244 Camera pose
• CPC Class Codes: G06T 2207/30248 Vehicle exterior or interior
• CPC Class Codes: G06T 7/73 using feature-based methods

Abstract

Systems and methods for determining heading of a traveling vehicle are provided. The systems and methods employ an image system to capture and match multiple distinctive features of an image area at a first and second point in time and to determine unit-vectors associated with the multiple distinctive features. A global positioning system (GPS) provides a translation vector for the first and second point and time and a coupled processor employs the unit-vectors and the translation vector to provide a corrected heading.

Claims

1. A system for determining heading that is mountable on a traveling vehicle, the system comprising:

an image system that captures multiple distinctive features in an area of interest at a first point in time and at a second point of time during traveling of the traveling vehicle, matches the multiple distinctive features captured at the first point of time and the second point of time, and determines a first unit-vector associated with a given matched distinctive feature based on the first point in time and a second unit-vector associated with the given matched distinctive feature associated with the second point in time for each of the multiple matched distinctive features;

a global positioning system (GPS) that determines a translation vector based on carrier phase information captured from the first point in time to the second point in time; and

a coupled processor that minimizes the error in an epipolar equation for each of the multiple matched distinctive features based on the respective first and second unit-vectors and the translation vector to determine a corrected heading, wherein the epipolar equation comprises data characterizing a distinctive feature captured at the first point in time and a distinctive feature captured at the second point in time.

2. The system of claim 1, further comprising an inertial measurement system that provides an initial leveling to the coupled processor, the coupled processor employing the initial leveling to directly solve the epipolar equation for heading.

3. The system of claim 2, wherein the inertial measurement system comprises an inertial measurement unit (IMU) and an inertial processor, the IMU provides changes in velocity and attitude to the inertial processor and the inertial processor determines estimates of position, heading and attitude.

6. The system of claim 1, wherein the coupled processor averages the determined corrected headings of each of the multiple matched distinctive features to directly compute heading for the system.

8. The system of claim 1, wherein the GPS comprises a GPS device and a GPS processor, the GPS device provides carrier phase information and the GPS processor determines the translation vector.

9. The system of claim 1, wherein the image system comprises an image sensor and an image processor, the image sensor captures the multiple distinctive features in the area of interest at the first point in time and at the second point of time during traveling of the traveling vehicle, and the image processor matches the multiple distinctive features captured at the first point of time and the second point of time, and determines the first unit-vector associated with a given matched distinctive feature based on the first point in time and the second unit-vector associated with the given matched distinctive feature associated with the second point in time for each of the multiple matched distinctive features.

14. The system of claim 1, wherein the GPS comprises a GPS device and a GPS processor, the GPS device provides carrier phase information and the GPS processor determines the translation vector, the image system comprises an image sensor and an image processor, the image sensor captures the multiple distinctive features in the area of interest at the first point in time and at the second point of time during traveling of the traveling vehicle, and the image processor matches the multiple distinctive features captured at the first point of time and the second point of time, and determines the first unit-vector associated with a given matched distinctive feature based on the first point in time and the second unit-vector associated with the given matched distinctive feature associated with the second point in time for each of the multiple matched distinctive features and the inertial measurement system comprises an inertial measurement unit (IMU) and an inertial processor, the IMU provides changes in velocity and attitude to the inertial processor and the inertial processor determined estimates of position, heading and attitude.

4. A system for determining heading that is mountable on a traveling vehicle, the system comprising:

an image system that captures multiple distinctive features in an area of interest at a first point in time and at a second point of time during traveling of the traveling vehicle, matches the multiple distinctive features captured at the first point of time and the second point of time, and determines a first unit-vector associated with a given matched distinctive feature based on the first point in time and a second unit-vector associated with the given matched distinctive feature associated with the second point in time for each of the multiple matched distinctive features;

a global positioning system (GPS) that determines a translation vector based on carrier phase information captured from the first point in time to the second point in time; and

a coupled processor that minimizes the error in an epipolar equation for each of the multiple matched distinctive features based on the respective first and second unit-vectors and the translation vector to determine a corrected heading;

wherein the epipolar equation is (x₁^L×

x₂^L)·

C_N^LT^N=0, where x₁^L is the first unit-vector, x₂^L is the second unit-vector, T^N is the translation vector and C_N^L is the transformation matrix from a navigation frame (N) frame to a local frame (L) frame, such that

5. The system of claim 4, further comprising an inertial measurement system that provides an initial heading to the coupled processor, the coupled processor employing the initial heading at a starting point for iteratively correcting the heading angle until a heading angle is provided that minimizes the error in the epipolar equation.

7. A system for determining heading that is mountable on a traveling vehicle, the system comprising:

an image system that captures multiple distinctive features in an area of interest at a first point in time and at a second point of time during traveling of the traveling vehicle, matches the multiple distinctive features captured at the first point of time and the second point of time, and determines a first unit-vector associated with a given matched distinctive feature based on the first point in time and a second unit-vector associated with the given matched distinctive feature associated with the second point in time for each of the multiple matched distinctive features;

a global positioning system (GPS) that determines a translation vector based on carrier phase information captured from the first point in time to the second point in time; and

a coupled processor that minimizes the error in an epipolar equation for each of the multiple matched distinctive features based on the respective first and second unit-vectors and the translation vector to determine a corrected heading;

wherein the coupled processor is a Kalman filter and the epipolar equation is δ

r=T×

(x₁×

x₂)·

φ

+(x₁×

x₂)·

δ

T, where x₁ is the first unit-vector, x₂ is the second unit-vector, T is the translation vector, where φ

=attitude error and δ

T=translation error, such that the Kalman filter resolves the attitude error φ and

δ

T is measured by the GPS.

10. A system for determining heading that is mountable on a traveling vehicle, the system comprising:

an image system that captures multiple distinctive features in an area of interest at a first point in time and at a second point of time during traveling of the traveling vehicle, matches the multiple distinctive features captured at the first point of time and the second point of time, and determines a first unit-vector associated with a given matched distinctive feature based on the first point in time and a second unit-vector associated with the given matched distinctive feature associated with the second point in time for each of the multiple matched distinctive features;

a global positioning system (GPS) that determines a translation vector based on carrier phase information captured from the first point in time to the second point in time;

a coupled processor that minimizes the error in an epipolar equation for each of the multiple matched distinctive features based on the first and second unit-vectors and the translation vector to determine a corrected heading; and

an inertial measurement system that provides an initial heading to the coupled processor, the coupled processor employing the initial heading at a starting point for minimizing the epipolar equation, wherein the epipolar equation comprises data characterizing a distinctive feature captured at the first point in time and a distinctive feature captured at the second point in time.

11. The system of claim 10, wherein the epipolar equation is (x₁^L×

x₂^L)·

C_N^LT^N=0, where x₁^L is the first unit-vector, x₂^L is the second unit-vector, T^N is the translation vector and C_N^L is the transformation matrix from a navigation frame (N) frame to a local frame (L) frame, such that

12. The system of claim 10, wherein the coupled processor averages the determined corrected headings of each of the multiple matched distinctive features to directly compute the heading for the system.

13. The system of claim 10, wherein the coupled processor is a Kalman filter and the epipolar equation is δ

r=T×

(x₁×

x₂)·

φ

+(x₁×

x₂)·

δ

T, where x₁ is the first unit-vector, x₂ is the second unit-vector, T is the translation vector, where φ

=attitude error and δ

T=translation error, such that the Kalman filter resolves the attitude error φ and

δ

T is measured by GPS.

15. A method for determining heading of a traveling vehicle employing an image system, an inertial system and a global positioning system (GPS), the method comprising:

capturing imagery, by the image system, in an area of interest and extracting multiple distinctive feature coordinates at a first point in time;

capturing imagery, by the image system, in the area of interest and extracting multiple distinctive feature coordinates at a second point in time;

matching, by the image system, the multiple distinctive feature coordinates captured at the first point of time and the second point of time to determine multiple matched distinctive features;

providing, from the image system, a first unit-vector associated with a given matched distinctive feature based on the first point in time and a second unit-vector associated with the given matched distinctive feature associated with the second point in time for each of the multiple matched distinctive features;

computing, by the GPS, a translation vector based on carrier phase information captured from the first point in time to the second point in time; and

minimizing, by a coupled processor, an epipolar equation for each of the multiple matched distinctive features based on the first and second unit-vectors and the translation vector to determine a corrected heading, wherein the epipolar equation comprises data characterizing a distinctive feature captured at the first point in time and a distinctive feature captured at the second point in time.

16. The method of claim 15, further comprising employing, by the coupled processor, an initial heading provided by the IMU at a starting point for minimizing the epipolar equation.

17. The method of claim 15, wherein the epipolar equation is (x₁^L×

x₂^L)·

C_N^LT^N=0, where x₁^L is the first unit-vector, x₂^L is the second unit-vector, T^N is the translation vector and C_N^L is the transformation matrix from a navigation frame (N) frame to a local frame (L) frame, such that

18. The method of claim 15, further comprising averaging, by the coupled processor, the determined corrected headings of each of the multiple matched distinctive features to directly compute the aligned heading.

19. The method of claim 15, wherein the epipolar equation is δ

r=T×

(x₁×

x₂)·

φ

+(x₁×

x₂)·

δ

T, where x₁ is the first unit-vector, x₂ is the second unit-vector, T is the translation vector, where φ

=attitude error and δ

T=translation error.

20. The method of claim 19, wherein a Kalman filter resolves the attitude error φ

and δ

T is measured by the GPS.