Digital underwater photogrammetric system for large scale underwater spatial information acquisition

An UNderwater Digital Photogrammetric System (UNDIPS) has been developed jointly by The University of Calgary and Canadian Hydrographic Services (CHS). An underwater photogrammetric model considering the lens distortion, housing cover corrections, and the medium refraction has been developed. It corrects the displacements of image points caused by the distortion and refraction so that the photogrammetric processing can be treated as a reduced central perspective transformation and modified direct linear transformation (DLT) can be applied. The calibration of the system is performed in two phases. This allows the examination of characteristics of the system associated with the cameras, the housing covers, and the medium refractions separately. With the current configuration, the achievable accuracy of object points which are 2–2.5 m from the cameras in the object space is 0.3 cm in the x and y directions and 1.0 cm in the z direction (depth).

Keywords:

• CCD camera
• digital imaging
• direct linear transformation (DLT) and calibration
• underwater photogrammetry