Estimating camera orientation from vanishing point location during sewer surveys

Abstract A method is presented by which camera orientation relative to the pipe axis may be recovered from a single frame of a survey video of a small-bore brick sewer. If it can be fully recovered, the pipe axis provides part of a frame of reference within which 3D descriptions of sewer shape may be expressed. The concept of the vanishing point is introduced and it is shown that the vanishing point position supplies information about the relative orientations of the camera and pipe axes. A method for the automatic detection of vanishing points is presented and used to analyse the camera motion underlying a number of sewer survey videos. The technique might form an active part of a more comprehensive image understanding system recovering pipe shape from survey videos and/or be used as an experimental tool during the design of such a system.