4. Stereo Vision System
The dual stereo vision system consists of two pairs of high speed, high resolution progressive scan CCD cameras. It captures stereo image pairs while the system drives at posted road speeds. The images are taken according to an operator-defined distance interval to provide full coverage of the roadway and its surroundings. By applying sophisticated photogrammetric triangulation technology, any point that appears in either set of two images can be located in a global coordinate system during digitization with Lambda Tech’s Feature Extraction Software.
In order to perform precise positioning, it is necessary to calibrate the entire system. The camera geometry, any lens distortions, the relative orientation parameters and the offset between the stereo vision system and the GPS/INS system must be determined. The camera geometry may be constant for a long time, but the relative and rotation offsets may change between different missions. Therefore, the entire system calibration is divided into two parts. The first part is the calculation of camera parameters using known control points in a test-field. The second is the calculation of the relative orientation and rotation offset based on a coplanarity equation and known constraints. In the second part, the position and rotation parameters of an image pair are used. No additional controls are required from the operator. This is well suited for an operationally smooth mobile mapping system.
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