Bathymetry and side scan imagery of SeaBeam 2000 multi-beam echo sounder on the Eastern Ulleung basin, East Sea of Korea (Japan Sea)

摘要

Seabeam 2000, a multi-beam echo sounder, is a new generation seafloor mapping system of which a single swath covers an angular range of -60/spl deg/ to 60/spl deg/ from the vertical direction with 121 beams. It provides high density and high quality bathymetry data along with side scan like amplitude imagery. The purpose of this article presents a post-processed Seabeam bathymetry and 121 returning amplitude imagery using digital image processing techniques. As a processor to convert vector-formatted Seabeam data into raster image mosaic, the following procedures are described: interpolation of unsampled beam data, removal of outliers, spatial registration of various types of data, and position correction of data in equi-spatial grid resolution. Even though the side scan imagery is fully corrected in real time for variations in ship speed and direction, it has low contrast due to the attenuation of side scan like returning amplitude signals along the horizontal range across the ship track. it has been observed that the levels of the returning acoustic signals, and adopted for contrast enhancement of digital side scan image. The results of the processed side scan image from the survey area (37/spl deg/ 00'N to 38/spl deg/ 30'N and 131/spl deg/ 00'E to 132/spl deg/ 00'E) reveal a newly discovered channels which develops into the lower slope regions (center of the survey area; depth 2,000 to 2,200 m) to deep bottom (2,300 m). There are many slope failures accompanied by slumping sliding, debris flows and turbidity currents at the southern high slope regions of Dok islands and around the submerged topographic high. On the other hand, large amounts of sediments were moved to deep water bottom along the channels during slope failures. The channel in this region affected by strong bottom current speed and directions.