Single Camera Speed Enforcement Using Sparse RGB Stereo
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional single camera systems for video-based vehicular speed enforcement face limitations in accurately detecting vehicle speed due to 2D imaging of a 3D world, poor quality of evidentiary photos, and conflicts between field of view requirements for speed detection and traffic monitoring, leading to estimation errors.
Innovation Solution
A system utilizing a primary camera and a low-cost secondary RGB camera for sparse stereo processing to estimate vehicle speed by tracking features and calculating height above a reference plane, providing improved accuracy and cost-effectiveness compared to conventional stereo camera systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single camera is used for speed detection, then the system cost is reduced, but the speed detection accuracy deteriorates due to limitations of 2D imaging of a 3D world
Solution Approach 1:
The patent introduces a temporal dimension to the single 2D camera system by analyzing video sequences over time. Through multi-frame analysis and optical flow computation, the system extracts speed information from temporal changes in the 2D image plane, effectively adding a time dimension that compensates for the lack of depth information in single-camera 2D imaging.
Solution Approach 2:
The system performs preliminary calibration to establish the relationship between pixel coordinates and real-world dimensions. By pre-determining camera parameters, field of view geometry, and scale factors during a calibration phase, the system prepares necessary reference data that enables accurate speed calculation from subsequent video frames without requiring real-time complex computations.
2Measurement precision
If the camera field of view is calibrated for speed detection accuracy, then speed measurement precision is improved, but the field of view width is reduced, limiting traffic monitoring capabilities
Solution Approach 1:
The system dynamically adapts its analysis based on the calibrated field of view geometry. Rather than using a fixed narrow FOV optimized for speed, the pre-calibrated geometric relationships enable accurate speed measurement across a wider, variable FOV by compensating for perspective distortions and varying distances through computational methods that adjust to different viewing angles and ranges.
3Device complexity
If conventional single camera systems are used, then device complexity is reduced, but evidentiary photo quality deteriorates due to retro-reflective properties of license plates requiring high dynamic range sensors
Solution Approach 1:
The system captures multiple frames at different exposure settings or at different time intervals, allowing it to periodically sample the scene under varying lighting conditions. By combining information from multiple temporal samples, the system overcomes the limitations of retro-reflective license plate materials that cause extreme dynamic range requirements, producing reliable evidentiary images without needing expensive high dynamic range sensors.
Data Source
AI summary
When performing video-based speed enforcement a main camera and a secondary RGB traffic camera are employed to provide improved accuracy of speed measurement and improved evidentiary photo quality compared to single camera approaches. The RGB traffic camera provides sparse secondary video data at a lower cost than a conventional stereo camera. The sparse stereo processing is performed using the main camera data and the sparse RGB camera data to estimate a height of one or more tracked vehicle features, which in turn is used to improve speed estimate accuracy. By using secondary video, spatio-temporally sparse stereo processing is enabled specifically for estimating the height of a vehicle feature above the road surface.