The Journal of the Marine Acoustics Society of Japan
Online ISSN : 1881-6819
Print ISSN : 0916-5835
ISSN-L : 0916-5835
Volume 31, Issue 1
Displaying 1-3 of 3 articles from this issue
  • Masao SAKATA, Akira ASADA
    2004 Volume 31 Issue 1 Pages 20-27
    Published: January 01, 2004
    Released on J-STAGE: August 16, 2011
    JOURNAL FREE ACCESS
    The bathymetry data obtained by multi-beam echo sounder is widely used and the amount is getting larger these days. But most of the existing systems to manage those data are made for common usage. So these systems cannot efficiently meet the demands varying by users who need more detailed bathymetry map for example. In this paper, first we suggest new data management system which improve these points. Next, two kinds of methods to correct errors of the bathymetry data are shown as functional components of new data management system. One is ray tracing in Earth ellipsoid and another is correction of error caused by horizontal acceleration in motion sensor. It was proved that the result of the new calculation method in ray tracing revises 5m of depth errors at a depth of about 5000m. And the error correction of the motion sensor after depth sounding was proved effective but needs more investigation.
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  • Toshihiro MAKI, Akira ASADA
    2004 Volume 31 Issue 1 Pages 28-38
    Published: January 01, 2004
    Released on J-STAGE: August 16, 2011
    JOURNAL FREE ACCESS
    Noises of multi-beam echo sounding cause wrong bathymetry data. In this paper we discuss two improved methods of data processing to reduce noises.
    (1) Time rigid motion compensation
    Ship motion (rolling, pitching, heaving) affects the location of each footprint. We improved the timing of ship motion used in compensation. We applied new method to real data, and we managed to get more precise bathymetry data than the old one.
    (2) Noise filtering using 3D angle of incidence
    There is a strong relationship between echo intensity and angle of incidence. Usually, 2D angle of incidence on a plane of projected fan beam is used for noise filtering. However, 2D angle of incidence isn't correct if the bottom is a slope. We introduced a new method to calculate 3D angle of incidence, and applied it to real data.
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  • 2004 Volume 31 Issue 1 Pages 62
    Published: 2004
    Released on J-STAGE: March 02, 2011
    JOURNAL FREE ACCESS
    Download PDF (35K)
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