Method of object location in airborne imagery using recursive quad space image processing

• US 8,155,433 B2
• Filed: 07/10/2008
• Issued: 04/10/2012
• Est. Priority Date: 07/10/2008
• Status: Active Grant

• Current Assignee: Goodrich Corporation (Rtx Corporation)
• Original Assignee: Goodrich Corporation (Rtx Corporation)
• Inventors: Chien, Greg T. H.
• Primary Examiner(s): Le, Vu
• Assistant Examiner(s): Abdi, Amara
• Application Number:
  US12/218,097
• Publication Number:
  US 20100008565A1
• Time in Patent Office: 1,370 Days
• Field of Search: 382/154, 382/280, 382/293, 701/301, 707/999.1
• US Class Current: 382/154
• CPC Class Codes: B64G 1/1021 Earth observation satellites
• CPC Class Codes: G06T 3/00 Geometric image transformations in the plane of the image

Abstract

A method and computer workstation are disclosed which determine the location in the ground space of selected point in a digital image of the earth obtained by an airborne camera. The image is rectangular and has four corners and corresponds to an image space. The image is associated with data indicating the geo-location coordinates for the points in the ground space corresponding to the four corners of the image, e.g., an image formatted in accordance with the NITF standard. The method includes the steps of: (a) performing independently and in parallel a recursive partitioning of the image space and the ground space into successively smaller quadrants until a pixel coordinate in the image assigned to the selected point is within a predetermined limit (Δ) of the center of a final recursively partitioned quadrant in the image space. The method further includes a step of (b) calculating a geo-location of the point in the ground space corresponding to the selected point in the image space from the final recursively partitioned quadrant in the ground space corresponding to the final recursively partitioned quadrant in the image space. The methods are particularly useful for geo-location from oblique reconnaissance imagery.

Claims

1. A method of determining the location in space of a selected point in a digital image of the earth obtained by a camera, the image comprising a rectangular image having four corners and corresponding to an image space, wherein the digital image is associated with data indicating the geo-location coordinates for the points in the ground space corresponding to the four corners of the image, comprising the steps of:

(a) performing independently and in parallel a recursive partitioning of both the image space and the ground space into successively smaller quadrants until a pixel coordinate in the image space assigned to the selected point is within a predetermined limit (Δ

) of the center of a final recursively partitioned quadrant in the image space, and

(b) calculating a geo-location of the point in the ground space corresponding to the selected point in the image space from the final recursively partitioned quadrant in the ground space corresponding to the final recursively partitioned quadrant in the image space;

wherein step (a) comprises the steps of;

1) calculating the intersection of two diagonal lines in the ground space;

2) finding the center point in the image space by equal subdivision;

3) determining whether the pixel coordinate of the selected point in the image is within the predetermined limit (Δ

) of the image center point in step

     2), and if not then;

4) finding the quadrant in the image that contains the selected point using the center determined in step

     2);

5) reducing the image space into a new image space corresponding to the quadrant found in step

     4);

6) calculating the coordinates of the selected point in the new reduced image space quadrant;

7) finding the quadrant in the ground space corresponding to the quadrant found in step

     4);

8) reducing the ground space into a new ground space corresponding to the found quadrant in step

     7);

9) calculating the geo-location coordinates of the corners of the new ground space found in step

     8); and

10) repeating steps 1-9 until the determination at step

     3) is answered in the affirmative.

2. The method of claim 1, wherein the predetermined limit (Δ

) is less than or equal to one pixel.

3. The method of claim 1, wherein the digital image comprises a digital reconnaissance image formatted in accordance with a format that contains geo-location coordinates of four image corners.

4. The method of claim 1, wherein the method is performed by a computing platform incorporated into the camera.

5. The method of claim 1, wherein the method is performed by a ground station receiving the image.

6. The method of claim 1, wherein the method is performed by a workstation storing the image and displaying the image on a display associated with the workstation.

16. The method of claim 1, wherein the geo-location coordinates for the corner points in the ground space corresponding to the four corners of the image are determined using data characterizing the performance of an optical system associated with the reconnaissance camera.

17. The method of claim 1, wherein the image comprises an image obtained at an oblique angle relative to the earth'"'"'s surface.

7. An image processing apparatus comprising:

a processing unit;

a machine-readable memory storing a digital image of the earth, the image comprising a rectangular image having four corners and corresponding to an image space, and

a display for displaying the image and a cursor movable by a user over the image to thereby select a point in the image;

wherein the memory further stores data associated with the image comprising the geo-location coordinates for the points in the ground space corresponding to the four corners of the image,

and wherein the memory further stores processing instructions for execution of the following steps;

(a) performing independently and in parallel a recursive partitioning of both the image space and the ground space into quadrants until a pixel coordinate in the image assigned to the selected point is within a predetermined limit (Δ

) of the center of a final recursively partitioned quadrant in the image space,

(b) calculating a geo-location of the point in the ground space corresponding to the selected point in the image space from the final recursively partitioned quadrant in the ground space corresponding to the final recursively partitioned quadrant in the image space; and

(c) displaying the geo-location calculated in step (b) on the display;

wherein step (a) comprises the steps of;

1) calculating the intersection of two diagonal lines in the ground space;

2) finding the center point in the image space by equal subdivision;

3) determining whether the pixel coordinate of the selected point in the image is within the predetermined limit (Δ

) of the image center point in step

     2), and if not then;

4) finding the quadrant in the image that contains the selected point using the center determined in step

     2);

5) reducing the image space into a new image space corresponding to the quadrant found in step

     4);

6) calculating the coordinates of the selected point in the new reduced image space quadrant;

7) finding the quadrant in the ground space corresponding to the quadrant found in step

     4);

8) reducing the ground space into a new ground space corresponding to the found quadrant in step

     7);

9) calculating the geo-location coordinates of the corners of the new ground space found in step

     8); and

10) repeating steps 1-9 until the determination at step

     3) is answered in the affirmative.

8. The image processing apparatus of claim 7, wherein the image processing apparatus comprises a workstation coupled to a ground station.

9. The image processing apparatus of claim 7, wherein the image processing apparatus comprises an image exploitation workstation.

10. The image processing apparatus of claim 7, wherein the image processing apparatus is incorporated into a land, sea or airborne unit.

18. The apparatus of claim 7, wherein the image comprises an image obtained by a camera oriented at an oblique angle relative to the earth'"'"'s surface.

11. In a workstation configured to display a digital aerial reconnaissance image and provide geo-location coordinates for a selected point in the image, the image corresponding to an image space, the area on the ground imaged corresponding to a ground space, the improvement comprising:

the workstation configured to perform the geo-location using as inputs the pixel coordinates of a selected point in the image and the geo-location coordinates of the four corners of the image; and

wherein the workstation performs independently and in parallel a recursive partitioning of both the image space and the ground space into quadrants until a pixel coordinate in the image space assigned to the Selected point is within a predetermined limit (Δ

) of the Center of a final recursively partitioned quadrant in the image space and calculates a geo-location in the ground space for a point corresponding to the selected point in the image when the limit is reached;

wherein the workstation includes a memory storing instructions for execution by a processing unit, and the processing unit performs the independent and parallel recursive portioning of the image space and the ground space using the instructions wherein the instructions implement the steps of;

1) calculating the intersection of two diagonal lines in the ground space;

2) finding the center point in the image space by equal subdivision;

3) determining whether the pixel coordinate of the selected point in the image is within a predetermined limit (Δ

) of the image center point in step

     2), and if not then;

4) finding the quadrant in the image that contains the selected point using the center determined in step

     2);

5) reducing the image space into a new image space corresponding to the quadrant found in step

     4);

6) calculating the coordinates of the selected point in the new reduced image space quadrant;

7) finding the quadrant in the ground space corresponding to the quadrant found in step

     4);

8) reducing the ground space into a new ground space corresponding to the found quadrant in step

     7);

9) calculating the geo-location coordinates of the corners of the new ground space found in step

     8); and

10) repeating steps 1-9 until the determination at step

     3) is answered in the affirmative.

12. The workstation of claim 11, wherein the workstation comprises an image exploitation workstation.

13. The workstation of claim 12, wherein the workstation is incorporated into a land, sea or airborne unit.

14. The workstation of claim 12, wherein the digital reconnaissance image comprises an image formatted in accordance with a format that contains geo-location coordinates of four image corners.

15. The workstation of claim 11, wherein the predetermined limit (Δ

) is less than or equal to one pixel.