| DUAN Yuewei,LIU Yongxue,LI Manchun,ZHOU Minxi,YANG Yuhao. 2016. Survey of reefs based on Landsat 8 operational land imager (OLI) images in the Nansha Islands, South China Sea. Acta Oceanologica Sinica, 35(10):11－19 |
| Survey of reefs based on Landsat 8 operational land imager (OLI) images in the Nansha Islands, South China Sea |
| 基于Landsat-8 OLI影像的南沙群岛岛礁遥感调查研究 |
| Received:December 20, 2015 Revised:May 05, 2016 |
| DOI：10.1007/s13131-016-0898-6 |
| Key words:remote sensing coral reefs OLI imagery Nansha Islands |
| 中文关键词: 遥感 珊瑚礁 OLI影像 南沙群岛 |
| 基金项目: |
| Author Name | Affiliation | E-mail | | DUAN Yuewei | Department of Geographic Information Science, Nanjing University, Nanjing 210023, China | | | LIU Yongxue | Department of Geographic Information Science, Nanjing University, Nanjing 210023, China
Collaborative Innovation Center for the South China Sea Studies, Nanjing University, Nanjing 210023, China | yongxue@nju.edu.cn | | LI Manchun | Department of Geographic Information Science, Nanjing University, Nanjing 210023, China
Collaborative Innovation Center for the South China Sea Studies, Nanjing University, Nanjing 210023, China | | | ZHOU Minxi | Department of Geographic Information Science, Nanjing University, Nanjing 210023, China | | | YANG Yuhao | Department of Geographic Information Science, Nanjing University, Nanjing 210023, China | |
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| Abstract: |
| A detailed survey of the reefs in the Nansha Islands' sea that are of strategic importance is conducive to their future development. In this study, a total of 50 Landsat 8 operational land imager (OLI) images were used to analyze the geological features and spectral characteristics of the Nansha reefs. The exposed islands/sandbanks, reef flats and sub-tidal reefs were identified with the near-infrared band, the red and green bands, and the blue band, respectively. Based on the relationships among various characteristics and bands illustrated in the OLI images, the maximum between-cluster variance threshold algorithm (OTSU method) and the mathematical morphology were employed to extract characteristic parameters of the spatial geometry of the reefs from top to bottom, which were subsequently operated by a series of post-processing methods such as vectorization, simplification and topological analysis. Among the 132 standalone reefs and 16 atolls that are identified in the study, four reefs have yet to be named in the Standard Names of Various Islands in the South China Sea and the website Nansha Islands Online (http://www.nansha.org/). Another 24 ones are exposed to the atmosphere even during high tides. Taiping Island with an area of 0.57 km2 represents the largest exposed geological feature. This study demonstrated the applicability of medium-resolution satellite images to derive the coral reef information effectively and thus provided information for the related departments that are responsible to manage the coast. An improved resolution of multispectral bands with the panchromatic band in higher spatial resolution (15 m for OLI image) is expected to provide an optimum satellite based approach to map marine habitats. |
| 中文摘要: |
| 南海珊瑚岛礁资源丰富，是我国开发、利用、保护与管控海洋的重要支点，战略价值重大。遥感为珊瑚岛礁资源调查提供了重要的技术支撑。研究基于2013年-2014年成像的50余景南沙群岛海域Landsat-8 OLI影像，分析了南沙珊瑚岛/礁光谱特征，通过OTSU分割算法从中提取岛屿、沙洲、礁坪、水下礁体、泻湖等信息。结果表明：（1）南沙群岛海域132个独立岛礁、16个群礁/组合环礁，其中有55个岛礁发育有泻湖。（2）研究发现4个岛礁未被列入《我国南海诸岛部分标准地名》。（3）在高潮时刻出露的珊瑚岛礁共计24个。 |
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