Detection and Classification of Sewer Pipe Junctions Using Reflective Photometric Stereo

We focus on the detection and classification of sewer pipe junctions during the initial survey stage of a 'soft' lnsituform lining process. Estimates are obtained of the diameter and orientation of interconnecting lateral pipes: smaller diameter pipes that join the main sewer from the side. These estimates are compared to a set of likely values of each and the member of this set closest to the estimated value is considered to represent ground truth. The proposed technique relies upon estimates of a) the distance from the camera to the lateral and b) the angle of intersection of the lateral and main pipes, both of which are obtained using a novel variant of Photometric Stereo termed Retlective Photometric Stereo.