Seafloor depth measurement technology has been changing recently from "individual soundings along the ships track" using single beam echo sounders to "swath-mapping" using multi-narrow beam echo sounder (MNBE) with the cross-fan beam techniques. This enables detection of the sea-bottom in topography the form of wide swath perpendicular to the ships track. We have developed the MNBE HS-500 II which uses a frequency of 500 kHz to detect sea-bottom depths to 50 m. Its main advantage is its ability to detect sea-bottom depths over a 90 degree swath angle at a transmission repetition rate of 2 times/sec resulting in a 1 degree resolution. Bathymetric data collectd by the HS-500 II is stored on tape along with ship heading and position that are sent from external sensors. We will also introduce a software package that we have developed along with the HS-500 II, which permits the off-line use of a personal computer to produce bathymetric charts covering wide areas seafloor from the stored data.
