2008 Volume 45 Issue 2 Pages 93-100
A bathymetric chart is a basic and useful tool for any study field in ocean science, and it is generally mapped from bathymetric data by multi narrow-beam echo-sounder (MNBES). However, MNBES is still expensive and inconvenient to utlize on a small boat at shallower coastal water e.g. shallow coral reef. Meanwhile, recently accuracy is improved both in location of GPS and in depth of fish finder (single echo sounder). This paper proposes a facile method for mapping bathymetric chart at shallow coastal water by using data of GPS and fish finder. Sea trial with GPS and fish finder was carried out at shallow water in Tateyama Bay, Chiba Prefecture, and the bathymetric chart was mapped by a 3D rendering software. The obtained bathymetric chart was compared with that mapped from data of MNBES, and data amendment was examined. This method can express the shape of the object on seabed of which dimension was twice larger than the distance between the successive two sounding points. The depth data should be amended, considering time change in tidal level and boat motion due to wave generated by other ships. The sounding points are concentrated on the boat track line, and thus introduction of anisotropic friction is effective in interpolating depth data between the track lines for 3D rendering.
