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。所开发的系统可以精确绘制海岸底部地形，获取准确的船舶位置，利用多波束声纳测量海底深度、基材和海草等底栖生物的分布，实时显示海底轮廓。由于回声测深仪扫描底深的宽度很短，由于间隔很宽，必须在样条之间插值底地形。作为一种遥感系统，它可以借助宽条宽的多波束声呐探测海底表面的三维形态，而无需插值对海底基材进行分类，并测量海草/海藻生物量。该系统利用精确的D-GPS、陀螺罗经和运动传感器，不仅可以定位船舶位置，还可以定位海底超声波束的位置。利用地理信息系统（GIS）对数据进行处理，提出了测绘海底地形和基材的方法。在突尼斯南部的Otsuchi湾、Aburatsubo湾和海山周围进行了实地研究。由于大池湾的研究对象是海草床，因此我们对海草的生态学和生物量进行了研究，作为海洋真相调查。在开发地图软件之前，我们研究了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，作为GIS在渔业和海洋学研究中的应用研究。测量海底底物和海底底栖生物生物量的传统方法是沿线样带或岩心取样，效率不高。结果表明，所开发的系统能够在1 ~ 100 m的水平尺度上精确地绘制出具有不同生态系统的海底环境。该系统对海岸带管理的实践具有重要的科学和社会意义。

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.