Abstract
Maintenance of tracks needs a lot of manpower at night because of manual inspection for long distance railroad sections. Therefore unmanned inspection is expected for the maintenance. The authors of this paper apply the detection of three dimensional center of gravity (abbreviated to D3DCG) for detecting deformation on track to contribute toward such unmanned inspection. D3DCG detects a right location of the center of gravity of an inspection equipment placed on a rail car when the car run on no deformed tracks, whereas D3DCG miss-detects the location when the car pass on deformed tracks.