With the rapid increase of the number of sewer pipes which have crossed their designed life, the sewer pipes are getting decrepit. On the other hand, the requirements of rebuilding the sewer pipes and the laying of optical fiber in the sewer pipes are increasing. Hence, in order to estimate the health of the sewer pipe accurately, frequent examination of the sewer pipes is becoming more and more important (Gunatilake et al. 1997 in Mach Vis Appl Indus Inspection V; Oosaka et al. 2005 Nippon Koei Tech forum 13:77–82; Saito et al. 2003 Nippon Koei Tech Forum 11:101–107, XU 1998 Pattern Recogn 31(2): 169–180; Kawasue 2008 Jpn Soc Mech Eng 90–97) [1–5].