Towards the recovery of extrinsic camera parameters from video records of sewer surveys

The aim of the work reported here is the recovery, from a single image taken inside a roughly cylindrical brick sewer pipe of diameter up to one meter, of the pose of the camera relative to the central axis of the pipe, It is shown that the vanishing point associated with the longitudinal mortar lines carries valuable information about the pose. A method for the automatic detection of this point is presented and used to analyse the camera rotations underlying a number of sewer survey videos. It is similarly shown how the angles between the images of the longitudinal lines can be used to recover information about camera pose. The techniques might form an active part of a more comprehensive image understanding system recovering the three-dimensional shape of a surveyed pipe from survey videos and/or be used as an experimental tool during the design of such a system.