Development of position recording system on structural surface using laser pointer

Surfaces of old structures are inspected by workers and the positions of the damaged places are manually recorded for their maintenance. In order to lighten this work, we propose a novel system to record position on structural surface by a laser pointer and a fisheye camera. When a worker traces the target surface with a laser light, its position in the camera image is detected after some image processing and the position is recorded directly on the surface image. In order to make the image processing easy and reliable, a tilted camera is placed away from workers, the subtraction of the images with the blinking circular beam of a laser pointer is utilized, and the pattern matching by templates of circles with several sizes is applied. Since this system needs no beacons for positioning, it is simple and inexpensive. It can be used in noisy environment with much traffic. We made experiments using the prototype system and confirmed that we can record position with good accuracy and reliability.