Data analysis of a low-cost bathymetry system using fishing echo sounders

The multi-beam echo sounder system with an accurate GPS can provide a detailed view of the seafloor and is successfully utilized in oceanography but its expense makes it impractical for many uses. The authors have therefore presented a low-cost system for surveying shallow sea bottom topography by using a fishing echo sounder in such a way that the many areas of the industry in which the information of the sea depth is required can easily use it to get the information they need. The system is based on sensor network technology, namely Micro Cube, which allows for the collection of the data from the fishing echo sounder via the Internet. However, the data obtained by the present system include noises or errors due to the reflection from bubbles or fishnets. In this paper, data analyses to erase noises or errors from measurements in the present system are discussed using the discrete wavelet transform and statistics. Experiments carried out in Rumoi, on the west coast of Hokkaido, Japan from July 2004 to December 2006 are studied for the examinations of data analyses for practical use.