MEASURING METHOD AND APPARATUS IN TUNNEL

摘要

PURPOSE:To allow measurement in tunnel by means of a still camera by irradiating the inner wall face in tunnel with a light beam from a predetermined position in the tunnel thereby forming a light trace of predetermined width on the cross-sectional wall face in the tunnel and then rotating the light beam stepwise around the predetermined position. CONSTITUTION:A still camera A2 is constituted to record image data on a magnetic disc and synchronized with stepwise rotation of a step motor 13 to photograph the trace of light beam L formed on a measuring cross-section of inner wall face in tunnel (a) every step. The camera A2 is supported by a measuring tripod 2a and leveled by means of a level 21a. A control section 14 controls stepwise rotation of the step motor 13 and interlocks the shutter of the camera A2 with the motion of the motor 13. Since the shutter of the camera A2 is opened only during one step operation and closed at a settling point between steps, S/N ratio can be enhanced by lowering the rotational speed of light beam even if the exposure time is short.