DREDGING METHOD

PROBLEM TO BE SOLVED: To provide a dredging method capable of efficiently and precisely lowering a glove to a prescribed position on water bottom by grasping the behavior tendency of the glove moving in water in the lowering of the glove into water. SOLUTION: A GPS antenna 5 or optical wave prism is mounted on the body of a dredger 1, a transmitter 4 for ultrasonic underwater position surveying device is mounted on a glove 3, and a receiver 7 therefor is mounted on the body of the dredger 1. The GPS antenna 5 or optical wave prism is mounted on the top of a boom 8. The underwater descending position of the glove 4 and the top position of the boom 8 are measured by GPS when the GPS antenna 5 is mounted and by an automatic tracking type distance measuring angle gauge arranged in a known point when the optical wave prism is mounted to grasp the behavior tendency of the glove 3 descending in water, and the following input position on the water level of the glove 3 is determined to input the glove 3.