Camera Calibration Using Ground Parallel Lines for Distance Measurement
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Solution Overview
Problem
Existing camera calibration processes are complicated and often impossible to perform in the field, hindering accurate height estimation from a single image.
Innovation Solution
A simplified method using image-to-ground homography and parallel lines on the ground, along with a camera focal length and known object height, to calibrate the camera and estimate real-world distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional camera calibration processes are used, then measurement precision is improved, but device complexity increases and ease of operation deteriorates
Solution Approach 1:
The patent extracts and utilizes only the essential elements needed for calibration: parallel lines on the ground plane and a single object of known height. By taking out the complex multi-object calibration procedures and focusing on these minimal necessary components, the system achieves accurate height estimation while dramatically simplifying the calibration process to something that can be performed in the field with minimal setup.
2Measurement precision
If traditional camera calibration processes are used, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The calibration process serves itself by using naturally occurring parallel lines in the environment (such as road markings, building lines, or any parallel structures) rather than requiring pre-prepared calibration targets or controlled environments. The system finds and utilizes these existing parallel structures automatically, making the calibration process as easy as pointing the camera at any scene with parallel lines, thereby dramatically improving ease of operation in field conditions.
3Ease of operation
If parallel lines and single object height are used for calibration, then ease of operation is improved, but measurement precision may deteriorate
Solution Approach 1:
The patent replaces complex mechanical calibration systems (physical calibration targets, precision measurement devices, controlled setup procedures) with a purely computational approach using homography matrices and geometric relationships. By substituting the mechanical calibration process with mathematical transformations based on parallel line intersections and perspective geometry, the system maintains high measurement precision while achieving remarkable ease of operation.
Data Source
AI summary
Example implementations include a method, apparatus and computer-readable medium for estimating a real world distance in an image, comprising obtaining an image from a camera installed in an environment and identifying, in the image, a first set of parallel lines on a real world ground plane and a second set of parallel lines on the real world ground plane. The implementations include determining a first intersection point of the first set of parallel lines and a second intersection point of the second set of parallel lines, identifying a ground line connecting the first intersection point and the second intersection point, and estimating an internal camera matrix based on a focal length and an image size associated with the camera. The implementations include calibrating the camera for real world distance measurement by determining a perpendicular vector to the ground line based on the internal camera matrix.