Vehicle Speed Measurement Using Dynamic Camera Angle Compensation
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Solution Overview
Problem
Existing methods for measuring vehicle speed using video cameras on moving vehicles suffer from low accuracy when movement is slow or in reverse directions, and are prone to errors due to perspective distortions, especially when the camera is not perpendicular to the surface.
Innovation Solution
A digital camera on a vehicle captures images at set intervals, with the camera angle constantly measured by an angular sensor, and the camera speed relative to the surface is calculated by analyzing the offset between frames, which is then corrected to determine the vehicle speed, accounting for camera height and perspective distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If correlation-based speed measurement method is used, then device simplicity is maintained, but measurement precision deteriorates when movement is slow or in reverse direction
Solution Approach 1:
The patent applies dynamics by making the camera angle adjustable and variable during measurement. The camera can be rotated to different angles relative to the vehicle motion direction, allowing the measurement system to adapt to different motion conditions (slow forward, reverse, varying speeds). This dynamic adjustment of camera orientation resolves the contradiction by enabling precise measurements across all motion states while maintaining correlation-based method simplicity.
2Device complexity
If camera is firmly fixated on static platform, then device complexity is reduced, but measurement precision deteriorates due to inability to compensate perspective distortions
Solution Approach 1:
The patent implements dynamics by transitioning from a static camera platform to a dynamic one where the camera angle can be actively adjusted. The camera mounted on the vehicle with adjustable orientation allows the system to change its viewing angle relative to the ground surface, enabling compensation for perspective distortions that occur at different camera angles while maintaining a relatively simple device structure.
3Adaptability or versatility
If camera is not perpendicular to surface, then adaptability to different mounting conditions is improved, but measurement precision deteriorates due to perspective projection distortion
Solution Approach 1:
The patent applies preliminary anti-action by measuring the camera angle relative to the vertical direction before performing speed calculation. This preliminary measurement of the camera orientation allows the system to pre-calculate or pre-compensate for the perspective projection distortion that will affect the measurement. By knowing the camera angle in advance, the system can correct the distortion effects and maintain high measurement precision regardless of the camera's mounting angle.
Data Source
AI summary
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.