Autonomous lock-on target tracking with geospatial-aware PTZ cameras
First Claim
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1. A video camera surveillance method comprising the steps of:
- providing a camera imaging a terrain space in a field of view of the camera, the field of view having a center;
acquiring images in a video stream from the camera;
forming an image pair of first and second images between two of the images;
aligning the first and second images with respect to each other;
performing a frame differencing operation on the image pair to form a binary resultant image including blobs corresponding to elements in the terrain space, the frame differencing operation comprising;
determining an overlapping region of the first and second images;
determining a high illumination threshold and a low illumination threshold; and
for each pixel in the overlapping region, identifying the respective pixel as a foreground pixel if (1) the respective pixel in the first image deviates from a corresponding pixel in the second image by at least the high illumination threshold, (2) the respective pixel in the first image deviates from pixels adjacent to the corresponding pixel in the second image by at least the high illumination threshold, and (3) the corresponding pixel in the second image deviates from pixels adjacent to the respective pixel in the first image by at least the low illumination threshold;
classifying one of the blobs as an object;
selecting the object as a target, the target having a centroid;
tracking the target by moving the camera toward the centroid by an amount corresponding to the distance between the centroid and the center of the field of view; and
continually repeating the tracking step as the target moves in the terrain space.
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Abstract
An autonomous lock-on target tracking system and method with geospatial-aware PTZ cameras includes a camera imaging a terrain space. The camera acquires images, and first and second images are aligned. A frame-differencing operation produces a resultant image including blobs corresponding to elements in the terrain space. One of the blobs is classified as an object and tracked as a target. The target is tracked by determining the distance between a centroid of the target and a center of a field of view of the camera, and instructing the camera to move through the distance. The distance is continually updated as the camera and the target move.
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Citations
16 Claims
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1. A video camera surveillance method comprising the steps of:
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providing a camera imaging a terrain space in a field of view of the camera, the field of view having a center; acquiring images in a video stream from the camera; forming an image pair of first and second images between two of the images; aligning the first and second images with respect to each other; performing a frame differencing operation on the image pair to form a binary resultant image including blobs corresponding to elements in the terrain space, the frame differencing operation comprising; determining an overlapping region of the first and second images; determining a high illumination threshold and a low illumination threshold; and for each pixel in the overlapping region, identifying the respective pixel as a foreground pixel if (1) the respective pixel in the first image deviates from a corresponding pixel in the second image by at least the high illumination threshold, (2) the respective pixel in the first image deviates from pixels adjacent to the corresponding pixel in the second image by at least the high illumination threshold, and (3) the corresponding pixel in the second image deviates from pixels adjacent to the respective pixel in the first image by at least the low illumination threshold; classifying one of the blobs as an object; selecting the object as a target, the target having a centroid; tracking the target by moving the camera toward the centroid by an amount corresponding to the distance between the centroid and the center of the field of view; and continually repeating the tracking step as the target moves in the terrain space. - View Dependent Claims (2, 3, 4, 5)
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6. A video camera surveillance method comprising the steps of:
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providing a camera imaging a terrain space in a field of view of the camera, the field of view having a center; acquiring images in a video stream from the camera; forming an image pair of first and second images between two of the images; performing a frame differencing operation on the image pair to form a resultant image including blobs corresponding to elements in the terrain space; detecting and discarding portions of the blobs which correspond to shadows by; selecting one of the blobs and defining a bounding box around the one of the blobs; defining a first half of the bounding box, an opposed second half of the bounding box, a first quadrant of the bounding box in the first half, and a second quadrant of the bounding box in the second half; computing a first column-sum ratio for the first quadrant; computing a second column-sum ratio for the second quadrant; and either discarding a portion of the one of the blobs in the second half of the bounding box if the first column-sum ratio is greater than a user-defined threshold, or discarding another portion of the one of the blobs in the first half of the bounding box if the second column-sum ratio is greater than the user-defined threshold; selecting a target from the blobs, the target having a centroid; tracking the target by moving the camera toward the centroid by an amount corresponding to the distance between the centroid and the center of the field of view; and continually repeating the tracking step as the target moves in the terrain space. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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13. A video camera surveillance method comprising the steps of:
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providing a camera imaging a terrain space in a field of view of the camera, the field of view having a center; acquiring images in a video stream from the camera; forming an image pair of first and second images between two of the images; aligning the first and second images with respect to each other; performing a frame differencing operation on the image pair to form a resultant image including blobs corresponding to elements in terrain space; selecting one of the blobs as a target, the target having a centroid, wherein the step of selecting one of the blobs as the target includes; identifying a first blob and a corresponding second blob in the resultant image; determining a first set of pixels in the second image which correspond to the first blob in the resultant image; determining a second set of pixels in the second image which correspond to the second blob in the resultant image; dilating both the first and second set of pixels in the second image to form a dilated first set of pixels and a dilated second set of pixels in the second image; measuring a first divergence between the first set of pixels and the dilated first set of pixels; measuring a second divergence between the second set of pixels and the dilated second set of pixels; classifying the first blob as the target if the first divergence is greater than the second divergence; and classifying the second blob as the target if the second divergence is greater than the first divergence; tracking the target by moving the camera toward the centroid by an amount corresponding to the distance between the centroid and the center of the field of view; and continually repeating the tracking step as the target moves in the terrain space. - View Dependent Claims (14, 15, 16)
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Specification