PROBLEM TO BE SOLVED: To heighten a subsidence measurement accuracy by reducing an influence exerted on subsidence measurement caused by surface tension, evaporation or a temperature change of stored water in a measuring system, and to perform a long-period continuous measurement without requiring replacement of the stored water, in a subsidence measuring system of the ground.;SOLUTION: In this nondestructive measuring method, water stored in a reference point water tank installed on a reference point is communicated with water stored in a measuring point water tank installed on a subsidence measuring point by an open channel pipe, to thereby acquire the same horizontal plane open to the atmosphere, of the water surface in the reference point water tank, the water surface in the measuring point water tank and the water surface in the open channel pipe. The primary level Hos of the water surface in the reference point water tank at a reference time before a subsidence measuring time, the primary level Hns of the water surface in the measuring point water tank at the reference time, the level Ho of the water surface in the reference point water tank an an optional subsidence measuring time, and the level Hn of the water surface in the measuring point water tank at the subsidence measuring time are measured. The subsidence quantity H on the subsidence measuring point at the subsidence measuring time is calculated by the equation H=(Hn-Ho)-(Hns-Hos).;COPYRIGHT: (C)2004,JPO
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