Abstract
Spurious multibeam depths have been eliminated in bathymetry measurements so far. However, those would occasionally become valuable in finding fishes, seagrass, seaweed, benthos, and thermal plume. So we had studied acoustical characteristics of seagrass by using multi-frequency transducers and a mutibeam echo sounder. As a result, the high frequency multi-beam echo sounder was very useful for observation of the growth of sea weed and seagrass. By means of calculating standard deviations of bottom echoes, we could divide echoes efficiently into bottom echoes and water column echoes. It followed that three dimensional measurement and visualization of seagrass and seaweed above the seabottom was carried out successfully.
