Stereo Camera External Parameter Calibration via Ground Plane
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Solution Overview
Problem
Existing methods for determining external parameters of a stereo camera require a reference point in the scene, which is not always feasible and can affect the accuracy of the external parameters, especially in scenarios where the application does not meet the required conditions.
Innovation Solution
A method and device that determine external parameters of a stereo camera using ground surface data without a reference point, by acquiring ground surface data, generating a first plane equation, determining the setting height, and calculating the pitch and inclination angles based on a plane normal vector, using techniques such as RANSAC and least squares fitting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference point in the scene is used to determine external parameters, then measurement precision is improved, but device complexity and ease of operation deteriorate due to high requirements for application scenarios
Solution Approach 1:
The patent extracts the ground surface information from the scene and uses it as a reference instead of requiring artificial reference points. By taking out the ground plane characteristics (flat surface, known geometry) from the general scene, the method eliminates the need for special reference objects while maintaining measurement accuracy.
Solution Approach 2:
The method enables the stereo camera system to determine its own external parameters autonomously using the ground surface that is already present in the scene. The system self-calibrates by detecting the ground plane and using its geometric properties, without requiring external reference points or complex setup procedures.
2Measurement precision
If a reference point is required for calibration, then measurement precision is improved, but ease of operation worsens due to complex calibration requirements
Solution Approach 1:
The patent extracts ground surface features from the captured image and uses them as calibration references. By extracting the ground plane information (which is naturally present in most outdoor scenes) instead of requiring artificial reference points, the method simplifies the calibration process while maintaining accuracy.
Solution Approach 2:
The calibration process becomes self-service by automatically detecting and utilizing the ground surface in the scene. The system performs self-calibration by identifying the ground plane and computing external parameters from its geometric properties, eliminating the need for manual setup of reference points.
3Measurement precision
If vertical edges perpendicular to the ground are used as reference, then measurement precision is improved, but adaptability deteriorates due to restrictive scenario requirements
Solution Approach 1:
Instead of using vertical edges in the scene to determine camera parameters, the patent inverts the approach by using the ground surface (which is more commonly available) as the reference. By inverting the reference from vertical features to horizontal ground features, the method expands applicability to scenarios where vertical edges may not be present.
Solution Approach 2:
The ground surface serves as a universal reference that can be used in diverse scenarios regardless of the presence of specific vertical features. The method makes the calibration process multi-functional by relying on the ground plane, which is universally present in outdoor environments, rather than scenario-specific vertical edges.
Data Source
AI summary
Embodiments of application discloses a method and device for determining external parameters of a stereo camera. The method comprises: acquiring ground surface data of a location of the stereo camera; generating, according to three-dimensional coordinates of each pixel in the ground surface data in a camera coordinate system corresponding to the stereo camera, a first plane equation in the camera coordinate system that conforms to the three-dimensional coordinates of the pixels; determining, according to a distance between the origin of the camera coordinate system and the ground surface, a setting height of the stereo camera; and generating, according to the first plane equation, a plane normal vector corresponding to the first plane equation; and determining, according to the plane normal vector, a pitch angle of the stereo camera and an inclination angle of the stereo camera. The external parameters of the stereo camera can be determined without using a reference point in a scene.