Camera Calibration Using Geographical Coordinates
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Solution Overview
Problem
Existing camera calibration methods often require multiple cameras, produce relative position data instead of absolute coordinates, and are cumbersome and inaccurate, limiting their effectiveness in smart city applications such as autonomous vehicle control and traffic management.
Innovation Solution
A method that uses geographical coordinates and angle measurements to transform 2D pixel coordinates into 3D geographical coordinates, allowing for absolute positioning of objects within a camera's view without the need for multiple cameras, by deriving modified projection data from camera characteristics and assuming objects lie on the Z=0 plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple cameras are used to determine 3D position coordinates, then positioning coverage is improved, but device complexity increases
Solution Approach 1:
The patent transforms the problem from 3D spatial reconstruction requiring multiple cameras to a 2D image plane transformation problem. By assuming objects lie on a planar surface (Z=0 in camera coordinate system), the solution maps 2D pixel coordinates directly to 3D world coordinates using a transformation matrix, eliminating the need for multiple cameras while maintaining positioning capability
Solution Approach 2:
The patent changes the calibration parameters from complex multi-camera extrinsic parameters to a simplified transformation matrix with fewer parameters. The calibration process determines parameters of the transformation matrix that maps 2D pixel coordinates to 3D world coordinates, reducing the number of required calibration parameters and simplifying the overall system
2Measurement precision
If known calibration algorithms are used, then camera positioning can be achieved, but implementation difficulty increases and time consumption increases
Solution Approach 1:
The patent performs preliminary calibration to establish a transformation matrix between 2D pixel coordinates and 3D world coordinates before actual positioning operations. This pre-computed transformation matrix enables rapid coordinate conversion during runtime without requiring complex real-time calculations, reducing both implementation complexity and processing time
Solution Approach 2:
The patent extracts and utilizes only the essential calibration information needed for positioning by assuming objects lie on a planar surface. This simplification extracts the core transformation relationship while discarding complex multi-dimensional reconstruction requirements, making the calibration process faster and easier to implement
3Ease of operation
If relative position coordinates are output, then camera frame of reference is maintained, but absolute geographical coordinates are not obtained
Solution Approach 1:
The patent introduces a transformation matrix as an intermediary that bridges the camera coordinate system and the world coordinate system. This matrix contains rotation and translation parameters that convert relative camera coordinates to absolute world coordinates, preserving the simplicity of camera frame operations while providing access to absolute geographical positioning information
Data Source
AI summary
Described is a method of calibrating a camera. The method comprises obtaining geographical coordinates of a selected physical point location within an image view of the camera and measuring an angle between an x-axis of a real-world coordinate system passing through said selected point location with respect to true north. The method includes using said obtained geographical coordinates, said measured angle, and projection data derived from characteristics of the camera to derive modified projection data for transforming a two-dimensional pixel coordinate system of the camera image view into a three-dimensional geographical coordinate system for point locations within the image view of the camera.