“…Computer-vision-based inspection enables rapid large-area measurement scalability with image sensors that are easily configurable with robotic systems [ 17 , 19 , 20 , 21 , 22 , 23 ] or unmanned aerial vehicles (UAVs) [ 24 , 25 , 26 ]. Multiple types of autonomous robotic systems, such as ring-type climbing robots, camera-equipped mobile robots, and movable fixtures with multiple degrees of freedom, have recently been employed to explore concrete structures and assist in maintenance [ 17 , 19 , 20 , 21 , 22 , 23 , 27 ]. Although robotic-platform-based inspection is a promising way forward for automation and scalability, the following limitations exist: (i) customized systems or auxiliary support systems are required for different structural components and this is often unsuitable for inaccessible surfaces; (ii) robotic platforms often have a short working distance from the target structure to achieve sufficient image resolution for reliable crack detection, i.e., a small field-of-view (FOV), which limits the range of coverage over a specified inspection duration; (iii) although the dimensions of the crack can be accurately identified in image coordinates, a lack of reference or calibration targets within a small FOV results in an erroneous estimation of the true dimensions of the crack in world coordinates; (iv) regarding bridge components, robotic platforms are difficult to operate without additional surface preparation due to the continuous exposure to degrading environmental conditions.…”