Development of a three-dimensional mapping system of biota and environment on the sea bottom with acoustics

本研究旨在开发便携式小型海底生物与环境三维制图系统。该系统可绘制精确的海岸地形图，获取精确的船位，利用多波束声纳测量海底深度、底质和海草等底栖生物的分布，真实的实时显示海底剖面。由于回声测深仪扫描的海底深度只有很短的扫描带宽度，海底地形必须插在横断面之间，因为宽的间隔。作为遥感系统，它可以借助宽扫描带宽度的多波束声纳探测海底表面的三维形态，无需插值即可对海底底质进行分类并测量海草/海藻的生物量。该系统利用高精度的D-GPS、陀螺罗盘和运动传感器，不仅可以定位船舶位置，还可以定位海底超声波束的位置。通过GIS数据处理，开发了海底地形和底质的制图方法。在突尼斯南部的Otsuchi湾、Aburatsubo湾和海山周围进行了实地研究。由于在大槌湾的研究对象是海草床，因此，作为海洋实况调查，我们对海草的生态和生物量进行了研究。在开发制图软件之前，我们对纳霍德卡溢油事故污染的潮间带生态系统的变化以及沿海地区的管理和保护进行了研究，作为GIS应用于渔业和海洋学研究的研究。传统的海底底质和底栖生物量测量方法是沿沿着潜水取样或岩芯取样，其效率不高。经验证，该系统可以精确地绘制海底表面的底部环境，生态系统在1到100米的水平尺度上变化。该系统不仅为海岸带管理实践提供了科学依据，也为海岸带管理实践提供了社会依据。

This study aimed to develop portable and small-size three-dimensional mapping system of marine organisms and environment on the sea bottom. The developed system can map precise coastal bottom topography acquiring accurate ship position, measuring bottom depths, substrate and distribution of benthic organisms such as seagrass with multibeam sonar, displaying bottom profile in real time. Since echosounders scan bottom depth with only short swath width, bottom topography must be interpolated between transects because of wide interval. It can sound three-dimensional form of bottom surface in aide of the multibeam sonar with wide swath width without interpolation classifying bottom substrate and measuring biomass of seagrass/seaweeds as a remote sensing system. The system also localizes not only the ship position but also bottom positions of ultrasound beams on the bottom by using accurate D-GPS, gyrocompass and motion sensor. We developed method mapping bottom topography and substrate by processing data with GIS. Field researches were conducted around Otsuchi Bay, Aburatsubo Bay and seamount in southern Tunisia. Since the research in Otsuchi Bay targeted seagrass beds, we made studies on ecology and biomass of seagrass as a sea truth survey. Before development of mapping software, we made researches on change in intertidal ecosystem polluted by the Nakhodka oil spill accident, and management and conservation of coastal areas as a research for GIS applying to studies on fisheries and oceanography. Conventional methods to measure bottom substrate and biomass of benthic organisms on the sea bottom are diving along a line transect or core sampling that are not efficient. It was verified that the developed system could map precisely bottom environment on the sea bottom surface with ecosystems varying in a horizontal scale of 1 to 100 m. The system contributes to not only scientific but also social domains for practice of coastal zone management.