Contour processing of sea beam bathymetric data.

Abstract

In 1983 the survey vessel "Takuyo",equipped with a Sea Beam system, was used for a continental shelf and seafloor topographical survey for earthquake prediction.‘A computer aided contour processing system of digital Sea Beam data, logged on magnetic tapes was employed. The authors developed two contouring programs, as on-board contouring program and an on-shore contouring program. The on-board contouring program was to draw contour lines of the sea floor topography in time sequence, by reading Sea Beam data little by little. Since this program has a characteristic in drawing contour maps in accordance with swath survey width, contour lines in the crossing area of tracks are drawn so as to overlap one another. As the contour maps produced by this program come directly from raw data, they give much information, such as whether or not erroneous data exists, whether or not data dispersion and discrepancy between tracks is large. Within a period of a survey we can efficiently re-examine the survey plan. By means of collective processing of all data of map area, the on-shore contouring program produces final maps that require little or no correction. For this object, the program has many functions: to remove erroneous data, to reduce data dispersion effectively, to change the degree of detail expression in accordance with depth (it being defined by the density of mesh data in drawing contour lines), and so on. We can make an effective processing plan of editing raw data with reference to the on-board map.