Transformation between Image and Map Coordinates

• US 20130162838A1
• Filed: 12/22/2011
• Published: 06/27/2013
• Est. Priority Date: 12/22/2011
• Status: Active Grant

• Current Assignee: Pelco (Schneider Electric SE)
• Original Assignee: Pelco (Schneider Electric SE)
• Inventors: Huang, Chien-Min, Su, Wei, Vaughn, Frank
• Granted Patent: US 9,749,594 B2
• Time in Patent Office: Days
• US Class Current: 348/169
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/20101 Interactive definition of point of interest, landmark or seed
• CPC Class Codes: G06T 2207/30232 Surveillance
• CPC Class Codes: G06T 7/73 using feature-based methods
• CPC Class Codes: G06V 20/52 Surveillance or monitoring of activities, e.g. for recognising suspicious objects recognising microscopic objects G06V20/69
• CPC Class Codes: H04N 7/181 for receiving images from a plurality of remote sources

Abstract

Systems and methods for transformations between image and map coordinates, such as those associated with a video surveillance system, are described herein. An example of a method described herein includes selecting a reference point within the image with known image coordinates and map coordinates, computing at least one transformation parameter with respect to a location and a height of the camera and the reference point, detecting a target location to be tracked within the image, determining image coordinates of the target location, and computing map coordinates of the target location based on the image coordinates of the target location and the at least one transformation parameter.

Claims

1. A method of identifying map coordinates of a location within an image captured by a camera, the method comprising:

selecting a reference point within the image with known image coordinates and map coordinates;

computing at least one transformation parameter with respect to a location and a height of the camera and the reference point;

detecting a target location to be tracked within the image;

determining image coordinates of the target location; and

computing map coordinates of the target location based on the image coordinates of the target location and the at least one transformation parameter.

2. The method of claim 1 wherein the at least one transformation parameter comprises a rotation angle and a tilt angle of the camera relative to the reference point.

3. The method of claim 2 wherein computing the map coordinates of the target location comprises computing a horizontal displacement angle and a vertical displacement angle from a center of the image to the target location within the image.

4. The method of claim 3 wherein computing the map coordinates of the target location comprises determining a position of the target location relative to an Earth-based coordinate system based on the horizontal displacement angle, the vertical displacement angle, the location and height of the camera, the rotation angle and the tilt angle.

5. The method of claim 4 wherein computing the at least one transformation parameter comprises computing a rotation matrix based at least in part on the rotation angle.

6. The method of claim 5 wherein the information relating to location and height of the camera comprises map coordinates of the camera, and wherein computing the map coordinates of the target location further comprises computing the map coordinates of the target location based on the rotation matrix, the map coordinates of the camera, and the map coordinates of the reference point.

7. The method of claim 1 wherein the target location is a location of an object detected in the image, and wherein the method further comprises tracking image coordinates and map coordinates of the object.

8. The method of claim 1 wherein the camera comprises a varifocal optical system, and wherein computing the at least one transformation parameter comprises:

identifying a focal length of the camera; and

computing the at least one transformation parameter based on horizontal and vertical fields of view associated with the focal length of the camera.

9. A target coordinate translation system comprising:

a camera configured to capture an image, wherein the camera has a known location and height and a system of image coordinates is defined with respect to the image;

a calibration module communicatively coupled to the camera and configured to identify a reference point within the image with known image coordinates and map coordinates and to compute at least one transformation parameter with respect to the location and height of the camera and the reference point;

an object tracking module communicatively coupled to the camera and configured to select a target location within the image and to identify image coordinates of the target location; and

a coordinate transformation module communicatively coupled to the calibration module and the object tracking module and configured to compute map coordinates of the target location based on the image coordinates of the target location and the at least one transformation parameter.

10. The system of claim 9 wherein the at least one transformation parameter comprises a rotation angle and a tilt angle of the camera relative to the reference point.

11. The system of claim 10 wherein the coordinate transformation module is further configured to compute a horizontal displacement angle and a vertical displacement angle from a center of the image to the target location within the image.

12. The system of claim 11 wherein the coordinate transformation module is further configured to determine coordinates of the target location relative to an Earth-based coordinate system based on the horizontal displacement angle, the vertical displacement angle, the location and height of the camera, the rotation angle and the tilt angle.

13. The system of claim 12 wherein:

the calibration module is further configured to compute a rotation matrix based at least in part on the rotation angle; and

the system further comprises a mapping module communicatively coupled to the coordinate transformation module and configured to identify map coordinates of the camera and to compute the map coordinates of the target location based on the rotation matrix, the map coordinates of the camera, and the map coordinates of the reference point.

14. The system of claim 9 wherein:

the camera comprises a varifocal optical system; and

the calibration module is further configured to identify a focal length of the camera and to compute the at least one transformation parameter based on horizontal and vertical fields of view associated with the focal length of the camera.

15. A system for identifying map coordinates corresponding to a location within a captured image, the system comprising:

a camera configured to capture an image, wherein the camera has a known location and height and a system of image coordinates is defined with respect to the image;

calibration means, communicatively coupled to the camera, for selecting a reference point within the image with known image coordinates and map coordinates and computing at least one transformation parameter with respect to the location and height of the camera and the reference point;

tracking means, communicatively coupled to the camera, for detecting a target location within the image and determining image coordinates of the target location; and

mapping means, communicatively coupled to the calibration means and the tracking means, for computing map coordinates of the target location based on the image coordinates of the target location and the at least one transformation parameter.

16. The system of claim 15 wherein the at least one transformation parameter comprises a rotation angle and a tilt angle of the camera relative to the reference point.

17. The system of claim 16 wherein the mapping means is further configured to compute a horizontal displacement angle and a vertical displacement angle from a center of the image to the target location within the image and to determine a position of the target location relative to an Earth-based coordinate system based on the horizontal displacement angle, the vertical displacement angle, the location and height of the camera, the rotation angle and the tilt angle.

18. The system of claim 17 wherein:

the calibration means is further configured to compute a rotation matrix based at least in part on the rotation angle; and

the mapping means is further configured to identify map coordinates of the camera and to compute the map coordinates of the target location based on the rotation matrix, the map coordinates of the camera, and the map coordinates of the reference point.

19. The system of claim 15 wherein:

the camera comprises a varifocal optical system; and

the calibration means is further configured to identify a focal length of the camera and to compute the at least one transformation parameter based on horizontal and vertical fields of view associated with the focal length of the camera.

20. A computer program product residing on a processor-executable computer storage medium, the computer program product comprising processor-executable instructions configured to cause a processor to:

identify information relating to a camera and a system of image coordinates relative to an image captured by the camera;

select a reference point within the image with known image coordinates and map coordinates;

compute at least one transformation parameter with respect to location and height of the camera and the reference point;

detect a target location to be tracked within the image;

determine image coordinates of the target location; and

compute map coordinates of the target location based on the image coordinates of the target location and the at least one transformation parameter.

21. The computer program product of claim 20 wherein:

the at least one transformation parameter comprises a rotation angle and a tilt angle of the camera relative to the reference point; and

the instructions configured to cause the processor to compute the map coordinates of the target location are configured to cause the processor to;

compute a horizontal displacement angle and a vertical displacement angle from a center of the image to the target location within the image; and

determine a position of the target location relative to an Earth-based coordinate system based on the horizontal displacement angle, the vertical displacement angle, the location and height of the camera, the rotation angle and the tilt angle.

22. The computer program product of claim 21 wherein:

the instructions configured to cause the processor to compute the at least one transformation parameter are configured to cause the processor to compute a rotation matrix based at least in part on the rotation angle;

the information relating to location and height of the camera comprises map coordinates of the camera; and

the instructions configured to cause the processor to compute the map coordinates of the target location are configured to cause the processor to compute the map coordinates of the target location based on the rotation matrix, the map coordinates of the camera, and the map coordinates of the reference point.