CAMERA-BASED SPEED ESTIMATION AND SYSTEM CALIBRATION THEREFOR
First Claim
1. A method for calibrating a vehicle speed estimation system that employs a camera having a set of camera parameters to estimate the speed of vehicles based on images received from the camera, the images defined in an image space and the vehicles and camera each belonging to a physical space and having an absolute position therein, the method comprising:
- a) receiving at a controller from the camera a calibration image stream comprising a first image of a vehicle captured at a first time and a second image of the vehicle captured at a second time, the first and second images having the same image space;
b) at a controller executing controller logic to identify in each of the first and second image a vehicle feature having a known dimension in the physical space, the identifying comprising determining a placement of the vehicle feature in the image space at each of the first and second times;
c) at the controller executing controller logic to define on the basis of the placement of the vehicle feature in the image space at each of the first and second times an absolute-position-independent relationship between an image space placement and a physical space position relative to the camera;
d) at the controller, using controller logic, applying the absolute-position-independent relationship between an image space placement and a physical space position relative to the camera in a speed estimation algorithm to determine the speed of a vehicle captured by the camera.
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Accused Products
Abstract
Provided is a visual vehicle speed estimation system based on camera output and calibration for such a vehicle speed estimation system. The calibration allows use of the system where the absolute camera position is unknown. Calibration determines an absolute-position-independent relationship between an image space placement and a physical space position relative to the camera. The calibration is done on the basis of camera output using vehicle features of known dimensions and some assumed physical constraints related thereto to provide a conversion relationship between image coordinates and physical space coordinates in a physical space defined in relation to the camera. This relationship is then used to estimate vehicle speeds based only on the visual information provided by the camera. Abstract is not to be interpreted as limiting.
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Citations
30 Claims
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1. A method for calibrating a vehicle speed estimation system that employs a camera having a set of camera parameters to estimate the speed of vehicles based on images received from the camera, the images defined in an image space and the vehicles and camera each belonging to a physical space and having an absolute position therein, the method comprising:
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a) receiving at a controller from the camera a calibration image stream comprising a first image of a vehicle captured at a first time and a second image of the vehicle captured at a second time, the first and second images having the same image space; b) at a controller executing controller logic to identify in each of the first and second image a vehicle feature having a known dimension in the physical space, the identifying comprising determining a placement of the vehicle feature in the image space at each of the first and second times; c) at the controller executing controller logic to define on the basis of the placement of the vehicle feature in the image space at each of the first and second times an absolute-position-independent relationship between an image space placement and a physical space position relative to the camera; d) at the controller, using controller logic, applying the absolute-position-independent relationship between an image space placement and a physical space position relative to the camera in a speed estimation algorithm to determine the speed of a vehicle captured by the camera. - View Dependent Claims (2, 3, 6, 7, 8, 11, 13, 14, 15)
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4. (canceled)
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5. (canceled)
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9. (canceled)
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10. (canceled)
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12. (canceled)
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16. A camera-based visual speed estimation system for estimating the speed of vehicles on the basis of video output from of a camera, the camera-based visual speed estimation system comprising:
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a) a controller camera input for receiving from the video output of the camera comprising at least first and second images of a travelling vehicle captured at respective first and second times, the first and second images being defined in an image space and the travelling vehicle and camera each belonging to a physical space and having respective absolute positions therein; b) a tangible controller in communication with the camera input and receiving therefrom the video data from the camera comprising at least the first and second images, the controller comprising calibration logic executable on the controller for causing the controller to; i. identify in each of the first and second image a vehicle feature having a known dimension in the physical space, the identifying comprising determining a placement of the vehicle feature in the image space at each of the first and second times; ii. define on the basis of the placement of the vehicle feature in the image space at each of the first and second times an absolute-position-independent relationship between an image space placement and a physical space position relative to the camera; iii. apply the absolute-position-independent relationship between an image space placement and a physical space position relative to the camera in a speed estimation algorithm to derive speed estimation data indicative of the speed of a vehicle captured by the camera; c) a controller output in communication with the controller for receiving from the controller the speed estimation data and outputting the speed estimation data. - View Dependent Claims (17, 18, 21, 22, 23, 26, 28, 30)
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19. (canceled)
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20. (canceled)
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24. (canceled)
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25. (canceled)
- 27. (canceled)
Specification