METHOD AND SYSTEM FOR MEASURING VEHICLE SPEED BASED ON MOVEMENT OF VIDEO CAMERA

• US 20120327240A1
• Filed: 09/04/2012
• Published: 12/27/2012
• Est. Priority Date: 03/10/2009
• Status: Active Grant

• Current Assignee: Topcon Positioning Systems Incorporated (Topcon Corporation)
• Original Assignee: Topcon Positioning Systems Incorporated (Topcon Corporation)
• Inventors: VOROBIEV, MICHAEL Y.
• Granted Patent: US 9,115,999 B2
• Time in Patent Office: Days
• US Class Current: 348/148
• CPC Class Codes: B60T 2250/04 Vehicle reference speed; Vehicle body speed
• CPC Class Codes: G01C 21/12 executed aboard the object being navigated; Dead reckoning
• CPC Class Codes: G01P 3/38 using photographic means
• CPC Class Codes: G01S 11/12 using electromagnetic waves other than radio waves
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/30252 Vehicle exterior; Vicinity of vehicle
• CPC Class Codes: G06T 7/20 Analysis of motion motion estimation for coding, decoding, compressing or decompressing digital video signals H04N19/43, H04N19/51

Abstract

A digital video camera is placed on a vehicle. The video camera is attached to the vehicle and is directed to a surface at a certain angle to the surface. The camera angle can change while vehicle is in motion. The camera angle is constantly measured by angular sensor (i.e., inclinometer). Images of the surface are projected onto a video matrix and transformed into a sequence of digital frames that are formed at a pre-set time interval. A speed of the video camera relative to the surface is calculated as a ratio of an off-set between the adjacent frames and the time interval between the frames. Then a known relative speed of the vehicle can be corrected by multiplication of the height of the camera (above the surface) by a coefficient that equals a ratio of the known vehicle speed and the measured camera speed.

Claims

1. A method for measuring movement of a video camera placed on a moving vehicle, the method comprising:

(a) acquiring a sequence of digital frames of the earth surface;

(b) correcting distortions of each frame;

(c) correlating adjacent frames, wherein the frames have maximum coincidence; and

(d) measuring off-set values between the adjacent frames,

wherein;

a simplified frame is created for each frame by approximation and filtering of the frame;

distortions are corrected for each simplified frame based on the camera parameters associated with each frame;

correlations of adjacent frames having maximum coincidence, are found;

correction off-set value is calculated based on changes in the camera parameters during generation of the frames; and

an actual off-set of portion of the surface is based on the off-set of the adjacent simplified frames corrected by the correction off-set value.

2. The method of claim 1, wherein the simplified frames are generated by transforming a color image into a monotone grey scale image.

3. The method of claim 1, wherein the simplified frames are generated by transforming a color image into a monotone color image.

4. The method of claim 1, wherein the simplified frames are generated by transforming a monotone grey scale image pixel-by-pixel into a binary image by comparing brightness values of all pixels against a pre-set threshold value.

5. The method of claim 1, wherein the simplified frames are generated by transforming an infra-red image into a monotone grey scale image.

6. The method of claim 1, wherein spherical aberration is corrected on the frames prior to generation of the simplified frames.

7. The method of claim 1, wherein the video camera is calibrated by using a calibration table and correction coefficients for spherical aberration are determined.

8. The method of claim 1, wherein portions of the adjacent simplified frames are used, wherein the portions have the same number and the same positioning of pixels.

9. The method of claim 1, wherein the finding of the correlation of the adjacent frames beginning from third is performed in neighborhood area of a point of maximum coincidence of images within the adjacent frames.

10. The method of claim 1, wherein the maximum correlation of the adjacent simplified frames is calculated by using an approximation function and by finding a correlation peak of this function.

11. The method of claim 10, wherein the approximation function is a parabolic function.

12. The method of claim 1, wherein the correlation of the adjacent simplified frames includes correlation of angles of the simplified frames having maximally coincident images.

13. The method of claim 1, further comprising calculating a current speed of the camera relative to the surface as a ratio of the off-set between the simplified frames and a time interval between the frames corresponding to the simplified frames.

14. The method of claim 1, further comprising correcting the camera height above the surface value by multiplying camera height by a ratio of known vehicle speed and a measured speed.

15. The method of claim 1, wherein the off-set of the camera is calculated as a sum of the off-sets between pairs of the adjacent simplified frames.

16. The method of claim 1, wherein the camera parameters include camera angle.

17. The method of claim 1, wherein the camera parameters include camera field of view.

18. The method of claim 1, wherein the camera parameters include camera height.

19. A system for measuring movement of a vehicle, the system comprising:

a video camera on the vehicle for generating images of an earth surface, wherein the video camera changes its angle relative to the earth surface as the vehicle moves over the earth surface;

a processing unit connected to the camera for processing the frames; and

a device for measuring camera angles relative to the earth surface,

wherein the processing unit approximates and filters the frames and calculates off-sets of earth surface images caused by changes in the camera angles relative to the earth surface, and

wherein;

a simplified frame is created for each frame by approximation and filtering of the frame;

distortions are corrected for each simplified frame based on camera parameters;

correlations of adjacent simplified frames, wherein frames having maximum coincidence, are found;

a correction off-set value is calculated based on changes in the camera angle; and

an actual off-set of a portion of the surface is calculated based on the off-set of the adjacent simplified frames corrected by the correction off-set value.