“…Several fast and efficient alternative methods to analyse the condition of a sewer pipe wall objectively were proposed [ 8 , 10 , 18 , 19 , 20 , 21 , 22 , 23 ]. These methods are acoustic [ 8 , 10 , 18 ], acoustic optical [ 19 ], electromagnetic [ 20 , 21 ], electroacoustic [ 22 ], ultrasonic [ 5 , 7 , 23 ] and laser-based [ 8 ] methods. These methods are not designed to work in CSOs.…”