METHOD AND APPARATUS FOR MEASURING HORIZONTAL POSITION OF TUNNEL EXCAVATOR

摘要

PURPOSE:To reduce time and labor required for measuring horizontal position drastically by arranging a magnetic field generating element under ground so as to have the central line of magnetic force directing straight while a magnetic field detecting element on a magnetic field detecting element guides crossing each other on a horizontal subtrate on the ground in such a manner that an interlinked surface is vertical to the guides while movable at the right angle thereto. CONSTITUTION:Magnetic field detecting elements 13 are moved along guides 10-1 and 10-2. With the movement, the level of change in the intensity of a magnetic field passing through an interlinked surface 14 of the magnetic field detecting element 13 varies as illustrated and the direction of the minimum value thereof corresponds to the direction 1 at which a magnetic field generating element 2 exists. Then, the magnetic field detecting element 13 is moved along the rectangular guides 10-1 and 10-2 to determine the direction 2 at which the magnetic field generating element exists by the same method when the direction 1 is determined. Thus, the intersection is determined between the two directions at which the magnetic field generating element existed as determined by moving the magnetic field detecting element 13 in two directions whereby the intersection P is decided to be the point right above the magnetic field generating element 2.