To obtain reliable 3D measurements from photogrammetric technique imaging, cameras must be calibrated to determine the value of the principal distance and various lens parameters. As zoom and auto-focus are known to change, the principal distance at the instant of imaging the use of laboratory-calibrated value may produce significant measurement errors. The value of other lens parameters also may change as a result of field imaging. Research was carried out to determine a reliable technique to obtain the value of the principal distance and other lens parameters in the field. This research was limited to a stereo-camera configuration where two digital cameras were used to map objects. The calibration involved simultaneous computations of the principal distance and other lens parameters of both cameras using a pair of stereo-images and a temporary control panel. The objective of the paper is therefore to discuss the testing of the developed technique and demonstrate its capacity for a high-accuracy field 3D measurement. Results of this research show that accuracy improvement is in the order of two times better than the conventional technique which uses self-calibration PDs and APs.
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