B43C-0581
Mapping seagrass beds and coral reefs in the coastal region of Vietnam using VNREDSAT-1 data
Thursday, 17 December 2015
Poster Hall (Moscone South)
Khin Va Lau1, Chi-Farn Chen1, Son Thanh Nguyen2, Cheng-Ru Chen3, Hoang-Son Tong Phuoc4 and Huu-Huan Nguyen4, (1)NCU National Central University of Taiwan, Jhongli, Taiwan, (2)NCU National Central University of Taiwan, Center for Space and Remote Sensing Research, Jhongli, Taiwan, (3)Center for Space and Remote Sensing Research, Chung-Li, Taiwan, (4)Institute of Oceanography - Vietnam Academy of Science and Technology, Nha Trang, Vietnam
Abstract:
Seagrass beds and coral reefs are two important ecosystems in the coastal zone. They play an important role to protect and shelter various marine organisms. Both seagrass beds and coral reefs could prevent the coastline from erosion. While seagrass stabilizes sediments and acts as a biofilter, coral reefs can control carbon dioxide in the ocean water. Besides, seagrass also provides direct food for many fish and marine animals. Therefore, mapping seagrass beds and coral reefs is very important for coastal management and conservation. In May 2013, Vietnam launched the first satellite for earth observations, called Vietnam Natural Resources, Environment and Disaster Monitoring Satellite (VNREDSAT-1). It is a great opportunity for environmental monitoring in the country using the data from this satellite. The objective of this study is to use the VNREDSAT-1 data to map seagrass beds and coral reefs in the coastal region of Ninh Hai district, Ninh Thuan province, Vietnam, where the seagrass still remains in good a condition. We processed the VNREDSAT-1 image through four steps: (1) Atmospheric correction using Second Simulation of the Satellite Signal in the Solar Spectrum radiative transfer model (6S), (2) Sun glint removal by using Hedley method, (3) Water column correction using the depth-variant index (DII) proposed by Lyzenga, and (4) Image classification using the maximum likelihood algorithm. The mapping results verified with the ground reference data showed a good overall accuracy of 75% and Kappa coefficient of 0.7. The total area of seagrass beds was approximately 323.09 ha, which mainly distributed in My Hoa and Thai An villages. The total area of coral reefs was approximately 564.42 ha, located along the coast and on outer area to seagrass and shoreline reefs. This study demonstrates the applicability of VNREDSAT-1 for underwater habitat monitoring. The results could be useful for natural resources managers to devise strategies for management and conservation of underwater ecosystems in Vietnam.
