| 摘要 |
PROBLEM TO BE SOLVED: To provide works detector capable of surely detecting unexecuted part of the works and having high resolution required for detecting the unexecuted part of the works such as groove executed on the water bottom. SOLUTION: An acoustic depth meter 3 placed on a float 2 is provided with a plurality of depth measuring parts A, B, C and D placed with a specific intervals on the bottom of the float 2 and the depth measuring part A, B, C and D are placed so that sound wave emitted from them overlap partly on the water bottom. When reflection wave returning by reflection at the unexecuted part of the works (groove) M among the sound wave emitted from each of depth measuring parts A, B, C and D is received by the neighboring depth measuring parts B and C, the existence of the unexecuted part of the works in the region S2 overlapping of sound wave emitted from the neighboring depth measuring parts B and C on the water bottom is detected and so the position of the unexecuted part of the works M can be more exactly detected than before.
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