“…Several systems have been developed to automate the inspection process in some specific environments, such as subway tunnels ( Zhang et al, 2014 ), flexible pavement surfaces ( Oliveira and Correia, 2013 ) ( Shi et al, 2016 ), bridge decks ( Prasanna et al, 2016 ), and buildings ( Yan et al, 2017 ) ( Chen et al, 2016 ). De Paz et al (2013 ) used a hexapod robot, named Hex-piderix, with a stereo camera to inspect the cracking on surfaces such as walls or roofs of buildings. Access to these places is sometimes difficult for the operators.…”