INERTIAL MEASUREMENT WITH AN IMAGING SENSOR AND A DIGITIZED MAP

• US 20120320195A1
• Filed: 08/23/2012
• Published: 12/20/2012
• Est. Priority Date: 07/10/2008
• Status: Active Grant

• Current Assignee: Andrew H. Hawkins, Gene D. Tener, Louis N. Glaros, Mark A. Bovankovich
• Original Assignee: Andrew H. Hawkins, Gene D. Tener, Louis N. Glaros, Mark A. Bovankovich
• Inventors: Hawkins, Andrew H., Bovankovich, Mark A., Glaros, Louis N., TENER, Gene D.
• Granted Patent: US 8,515,611 B2
• Time in Patent Office: Days
• US Class Current: 348/139
• CPC Class Codes: F41G 7/34 based on predetermined target position data
• 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: G01S 13/876 Combination of several spaced transponders or reflectors of known location for determining the position of a receiver G01S13/874 takes precedence
• CPC Class Codes: G01S 17/875 for determining attitude
• CPC Class Codes: G01S 5/163 Determination of attitude using inertial means G01C9/00; control of attitude G05D1/49
• CPC Class Codes: G05D 1/106 Change initiated in response to external conditions, e.g. avoidance of elevated terrain or of no-fly zones
• CPC Class Codes: G06T 2207/10032 Satellite or aerial image; Remote sensing
• CPC Class Codes: G06T 2207/30252 Vehicle exterior; Vicinity of vehicle
• CPC Class Codes: G06T 7/75 involving models

Abstract

The present invention relates to a system and method for determining vehicle attitude and position from image data detected by sensors in a vehicle. The invention uses calculated differences between the locations of selected features in an image plane and the location of corresponding features in a terrain map to determine the attitude of the vehicle carrying the sensors with respect to a ground frame of reference.

Claims

1. A method of electro-optical absolute attitude determination of an object comprising:

capturing a frame of image data of a first scene with a detector or sensor that measures angles of detected features within the captured frame of image data with respect to the detector'"'"'s boresight reference relative to the object;

identifying at least three features from the captured frame of image data of said first scene by

selecting features within the pixel space of the captured frame of image data; and

computationally correlating said identified features to features in a map to determine corresponding map locations of said identified features and a location of the object within the map;

calculating, with a processor, the absolute attitude based on the difference between the locations of the at least three features in the captured frame of image data and the locations of the correlated features in the map by

transforming the correlated features from the map into a first set of object space angular coordinates based on the location of the object within the map and the measured angles of the correlated features to generate horizontal, vertical, and arc coordinate values.

2. The method of claim 1, said captured frame of image data including object-relative locations of passively-detected transmitter beacons wherein at least one feature of said at least three features comprises a transmitter beacon location.

3. The method of claim 1, said captured frame of image data comprising visible-spectrum imaging data.

4. The method of claim 1, said map comprising a terrain map.

5. The method of claim 1, wherein measuring angles of detected features with respect to the detector'"'"'s boresight reference relative to the object includes calculating a line-of-sight (LOS) unit vector from the detector or sensor to an identified feature;

and

where the LOS unit vector is computed as a function of LOS angles (and) measured relative to the detector or sensor, such that the unit vector (u) is given by the expression;

6. The method of claim 1, the method further comprising:

capturing a second frame of image data of the first scene with a second detector that measures angles of detected features within the second frame of image data with respect to the second detector'"'"'s boresight reference relative to the object; and

identifying said selected features in the captured second frame of image data of said first scene;

where transforming the selected features into a set of object space angular coordinates further includes transforming the selected features into said set of object space angular coordinates based on the measured angles from the second detector, and a known line-of-sight (LOS) boresight angle between the first and second detectors.

7. The method of claim 6, where the first and second detectors have different detection wavelength ranges.

8. A device for electro-optically determining absolute attitude of an object, the device comprising:

an imaging sensor that captures a frame of image data of a first scene and that measures the angles of detected features within the captured frame of image data with respect to the sensor'"'"'s boresight reference relative to the object;

a feature identification unit that identifies at least three features in captured frame of image data, the feature identification unit comprising

a feature selection unit that selects features within the pixel space of the captured frame of image data; and

a feature correlation unit that correlates said identified features to a map;

a feature location unit that determines corresponding map locations of the correlated features and a location of the object within the map; and

an attitude calculator that calculates the absolute attitude based on the difference in the locations of at least three features in the frame of image data and the locations of the correlated features in the map, the attitude calculator comprising

a space transformation module that transforms the correlated features from the map into a first set of object space angular coordinates based on the location of the object within the map and the measured angles of the correlated features to generate horizontal, vertical, and arc coordinate values.

9. The device of claim 8, said captured frame of image data comprising object-relative locations of passively-detected transmitter beacons wherein at least one feature of said at least three features comprises a transmitter beacon location.

10. The device of claim 8, said imaging sensor comprising a visible-spectrum imaging sensor.

11. The device of claim 8, further comprising a memory unit that stores said map, wherein the map includes a terrain map.

12. The device of claim 8, the device further comprising:

a second imaging sensor that captures a second frame of image data of the first scene and measures the angles of detected features within the second frame of image data with respect to the second detector'"'"'s boresight reference relative to the object;

where the feature identification unit identifies the selected features in the second frame of image data; and

where the space transformation module transforms the selected features into a set of object space angular coordinates by also transforming the selected features into said set of object space angular coordinates based on the measured angles from the second detector, and a known line-of-sight (LOS) boresight angle between the first and second detectors.

13. The device of claim 12, where the first and second detectors have different detection wavelengths.

14. A non-transitory computer-readable medium having embodied thereon instructions which, when executed by a computing device, cause the device to perform a method of electro-optical absolute attitude determination of an object comprising:

capturing a frame of image data of a first scene with a detector or sensor that measures angles of detected features within the captured frame of image data with respect to the detector'"'"'s boresight reference relative to the object;

identifying at least three features from the captured frame of image data of said first scene by

selecting features within the pixel space of the captured frame of image data; and

computationally correlating said identified features to features in a map to determine corresponding map locations of said identified features and a location of the object within the map;

calculating, with a processor, the absolute attitude based on the difference between the locations of the at least three features in the captured frame of image data and the locations of the correlated features in the map by

transforming the correlated features from the map into a first set of object space angular coordinates based on the location of the object within the map and the measured angles of the correlated features to generate horizontal, vertical, and arc coordinate values.

15. The medium of claim 14, said captured frame of image data including object-relative locations of passively-detected transmitter beacons wherein at least one feature of said at least three features comprises a transmitter beacon location.

16. The method of claim 14, said captured frame of image data comprising visible-spectrum imaging data.

17. The medium of claim 14, said map comprising a terrain map.

18. The medium of claim 14, wherein measuring angles of detected features with respect to the detector'"'"'s boresight reference relative to the object includes calculating a line-of-sight (LOS) unit vector from the detector or sensor to an identified feature;

and

where the LOS unit vector is computed as a function of LOS angles (and) measured relative to the detector or sensor, such that the unit vector (u) is given by the expression;

19. The medium of claim 14, the method further comprising:

capturing a second frame of image data of the first scene with a second detector that measures angles of detected features within the second frame of image data with respect to the second detector'"'"'s boresight reference relative to the object; and

identifying said selected features in the captured second frame of image data of said first scene;

where transforming the selected features into a set of object space angular coordinates further includes transforming the selected features into said set of object space angular coordinates based on the measured angles from the second detector, and a known line-of-sight (LOS) boresight angle between the first and second detectors.

20. The medium of claim 19, where the first and second detectors have different detection wavelength ranges.