PURPOSE: To survey the position of an under ground structure non-destructively and accurately by a float.
CONSTITUTION: A small chamber 20 with an outer opening at a specific part of a top surface wall body of a cylindrical structure 1 which is installed underground and a float 21 with a needle-shaped tip and an adjusting string 23 where one edge is connected to the float 21 and the other is led to the inside of the structure 1 watertightly is housed. After the structure is installed underground, a measurement hole 6 is punched from a corresponding position of a ground surface 3 and then the measurement hole 6 and the small chamber 20 are filled with water for floating the float 21 from a reference point Q to a water surface. The other edge of the adjusting string 23 is pulled from the inside of the structure 1 and the lower edge of a weight 9 which is suspended from the corresponding position of the ground surface while it is tensioned is allowed to contact a needle-shaped tip R of the float 21, thus obtaining an upper edge position P of a weight suspension string 10 at the time of contact. The three-dimensional position of the structure 1 is determined by the ground surface coordinates of the position P and the vertical distance from the position P to the reference point Q.
MIYAJIMA TOSHIKAZU
MIYAUCHI YOSHIKAZU
