| 摘要 |
PROBLEM TO BE SOLVED: To detect a sea bottom surface and a sea surface existing in a three- dimensional acoustic image as a two-dimensional plane area without using an altitude measuring device and a water pressure sensing depth indicator. SOLUTION: A horizontal two-dimensional plane area is sequentially extracted from a scanning area of an acoustic sensor 10 with a sensor altitude (the assumed depth) as a parameter, and an average value is calculated by dividing the sum total by the data number of a base set by determining the sum total of target detecting signals on this two-dimensional plane area. This average value is a value for indicating an occupying rate of a target in the two-dimensional plane area. Then, the sensor altitude (the assumed depth) corresponding to the most prominent average value is determined, and this value is determined as a vertical separate distance between the acoustic sensor 10 and the sea bottom surface, that is, the sensor altitude. Thus, even when the sensor altitude and the sensor depth are unknown, the sea bottom surface and the sea surface can be easily detected only by the acoustic sensor 10.
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