Chapter 2 Estimation of sea bottom density profile through analysis of ultrasonic echo signals

Abstract

The density profiles of soft muddy sea beds provide as fundamental data for addressing the shoaling of waterways and anchorages and improvement of the coastal marine environment. As far as we know, no method exists for measuring the density of soft-mud sea beds using ship-mounted measuring equipment. This study develops a ship mounted mud-layer detecting system that utilizes wideband narrow-beam underwater acoustic pulses for the purpose of obtaining vertical density profiles of the soft sea bottom several tens of meters deep while the survey vessel is underway. This system collects the ultrasonic echoes from the sea bottom, digitizes the data, and stores them in the hard disk of the onboard computer. Then, these ultrasonic echoes are processed with analyzing software through off-line processing to obtain the vertical density profiles of the sea bottom. The prototype of this system has been operated at Kumamoto Port (Kyushu, Japan) and other domestic ports and harbors. This paper describes the outline of the prototype system and the data analysis method and presents the results of estimation of the vertical density profiles of Kumamoto Port.