Development and Applications of a Total Station with a Built-in Crack Scale

Cracking is one of the most important features to identify the current condition states of concrete structures. Structural engineers can analyze the cracking patterns and its extension over a period of time to make proper decisions on structural repair and/or rehabilitation. In this research, a crack detection system called “KUMONOS”, which is a total station equipped with a built-in crack scale is described. The system generates a crack map with higher accuracy without reaching the structure within arm length, providing safer working environment to the inspector compared to the traditional close-up visual inspection method. Furthermore, the data obtained by KUMONOS can be integrated into the data from a 3D laser scanner or photogrammetry. The crack widths determined by the built-in crack scale varies depending on his/her experience and prejudice, causing certain amount of dispersion in the determination of crack widths. In order to minimize this dispersion, a methodology was developed to calibrate the human eye by providing a short training course. This paper describes the theory of crack measurement using KUMONOS system, calibration training program, and some examples of the combined usage of KUMONOS with photogrammetry and a 3D laser scanner.