Research On Strategic Value Evaluation Of The Islands And Reefs In The Nansha Islands

The Nansha Islands, as China’s inherent territory, are not only the frontline positions of the sea defences, but also the important base of the marine resource, directly related to the objective needs of coastal rights protection, energy resources exploitation and regional peaceful development. Since1970s, countries such as Vietnam, Philippines, Malaysia and Brunei, have illegally occupied or controlled the islands and reefs in the Nansha Islands by military action, avowedly infringing the maritime rights and the territorial sovereignty and seriously threating the national security and diplomatic relations.In response to the phenomenon of aggravated dispute for the ialands and reefs in the Nansha Islands and utterly lacking in strategic value research for the ialands and reefs in the Nansha Islands, this research, with the support of Landsat OLI remote sensing image, realized the strategic value evaluation for the islands and reefs in the Nansha Islands, by introducing and modifying gravity model, hoping to provide a reference for national marine rights protection and marine development strategy formulation.The main contents of this research are listed as follows:(1) Aiming at the spectral signatures of different coral cover types, using the threshold value segmentation method of OTSU layer-by-layer, six coral cover types, including:high-tide sandy, intertidal sandy, low-tide sandy, live corals/sand, dead corals and lagoon sediment, and the background information of the water can be extract. After that, through the processes of grid binarization and vector quantization, the shape element of the reef platform can be established. Thus, this research realized the geographic information extraction automatically for the islands and reefs in the Nansha Islands.(2) Deeply analyze the strategic value of the islands and reefs in the Nansha Islands, including five aspects:natural value, economic value, shipping value, political value and military value. In addition, the islands and reefs in the Nansha Islands also affected by the tropical cyclones. This research quantized each impact factor by the s patial analysis function of GIS, and then built the evaluation index system to calculate the own comprehensive value of the islands and reefs in the Nansha Islands. Moreover, in view of the interaction for the islands and reefs in the Nansha Islands, this research introduced and modified the gravity model to establish the strategic value evaluation model for the islands and reefs in the Nansha Islands.(3) According to the morphological characteristics and the distribution status, islands and reefs in the Nansha Islands can be divided into four categories, including: group reefs, multi-reefs, atolls and platform reefs. Using the strategic value evaluation model for the islands and reefs in the Nansha Islands, the four categories can be evaluate respectively, to provide support for the management, exploitation and conservation of the islands and reefs in the Nansha Islands.The results show that:(1) The order of the strategic value for the group reefs in the Nansha Islands from high to low is:Tizard Banks, Thitu Island and Reefs, Union Banks and Reefs, Loaita Bank and Reefs, and North Danger Reefs.(2) The order of the strategic value for the multi-reefs in the Nansha Islands from high to low is:Zhongye-Tiexian, Meijiu-Tiezhi, Investigator Shoal, Mahuan-feixin, and Houteng-Gongzhen.(3) Among the atolls in the Nansha Islands, the strategic value of Meiji Reef, Wufang Reef, Danwan Reef, Renai Reef, Liumen Reef, Siling Reef, Yongshu Reef, Bisheng Reef, Dong Reef, Bo Reef and Xinyi Reef are higher.(4) Among the platform reefs in the Nansha Islands, The strategic value of Taiping Island and Zhongye Island are the highest. In the group reefs, the strategic value of Beizi Island is the highest in the North Danger Reefs; the strategic value of Zhongye Island is the highest in the Thitu Island and Reefs; the strategic value of Shuanghuang Shoal is the highest in the Loaita Bank and Reefs; the strategic value of Taiping Islands is the highest in the Tizard Banks; the strategic value of Jinghong Island is the highest in theUnion Banks and Reefs. Except the group reefs, the strategic value of Nanwei Islands, Xiyue Islands, Mahuan Islands, Langkou Reef, Feixin Reef, Huayang Reef, Anbo Shoal are higher.