SURVEYING INSTRUMENT FOR TUNNEL EXCAVATOR

PURPOSE: To rearrange the surveying instruments and targets for controlling a tunnel excavator along a scheduled tunnel line efficiently. CONSTITUTION: A surveying instrument 4 for measuring the coordinates of a target 2 installed on a tunnel excavator 1 while collimating is mounted, together with targets 6a, 6b installed at known positions in the rear thereof, on frames 3, 5a and 5b which can travel on a track 8. The frames 3, 5a and 5b are shifted independently, by means of the surveying instrument 4, to desired positions which can be collimated mutually. The traveling wheel 24 of the frame 3, 5a, 5b can be set removably on the track 8 and the frame 3, 5a, 5b is provided with a gripper member 26, 26a, 26b gripping the wall face of tunnel detachably through a jack.