Abstract
Field evaluation of sounding accuracy in the multi-narrow beam echosounder, SeaBeam 2112, on R/V Kairei was carried out in the seafloor with a depth of deeper than 9,000 m. Bathymetric data were gathered while the ship holds on station. Variations of pitch, roll, and heave indicate that the ship was so stable that the motion of the ship except for heading did not affect for soundings. The depth uncertainty in each beam was estimated by forming the ratio of the standard deviation of the soundings in each angular bin to their mean. The soundings in observation range from 8,500 m to 10,900 m. The uncertainty in most beams from beam angle -24° to 27° is below the quality assurance (< 0.5%) demanded by the manufacturer. That of outer beams from the beam angle -24° and 27° is larger than 0.5% because of beam pointing errors by motion of the ship and topographic relief. The uncertainty of all beams at a constant heading was lower than 0.5%. The depth uncertainty near the vertical beam was lower than 0.1%. Soundings by SeaBeam 2112 on R/V Kairei in deeper than 10,900 m of water depth satisfy Order 1b of Standards for Hydrographic Surveys (S-44) by the International Hydrographic Organization.
