遥感和GIS支持下的九段沙岸线提取及变迁研究

在遥感和GIS的支持下,利用集成了非监督分类、地图综合、离散地物去除和岸线追踪等技术的shoreline-Extractor软件,解译上海市九段沙自然保护区2001年、2005年和2008年的岸线信息;对解译的目标岸线分别进行空间分辨率为30 m,90 m,150 m,210 m和270 m的重采样,计算其分维数,并进行岸线长度、沙洲面积和分形特征的分析,进而对九段沙岸线变迁的重点区域进行了分析。研究表明,随时间推移,九段沙的上沙、中沙和下沙3个沙洲淤长的部位并不一致,其中上沙北部区域、中沙东北和西南区域、下沙东北和西南区域淤长较为明显;岸线长度与沙洲面积的变化区域几乎一致,即上沙增长较快、下沙次之、中沙缓慢;九段沙岸线具有显著的分形性质,整体分维数呈增加态势,其中上沙和中沙的分维数小于整体分维数,而下沙的分维数大于整体分维数。

Shoreline Extraction and Change Analysis of the Jiuduansha Islands with the Support of Remote Sensing and GIS Technologies

With the support of remote sensing and GIS technologies,the shoreline information of the Jiuduansha Wetland Nature Reserve in Shanghai obtained in 2001,2005 and 2008 was interpreted respectively through an ArcInfo embedded software,shorelineExtractor,which integrates unsupervised classifiers,map generalization,discrete surface features removal and shoreline tracking.The extracted shorelines were re-sampled at 30,90,150,210,and 270 m respectively to compute the fractal dimensions.A consequent analysis of the shoreline lengths,shoal areas and key positions experiencing growth was conducted in detail.The results demonstrate that there are remarkable differences between the positions of silt growth in three shoals of the Jiuduansha Islands,i.e.upper,middle and lower shoals.The silt growth is dramatically fast in northern upper shoal,northeastern and southwestern middle shoal,and northeastern and southwestern lower shoal.The growths of shoreline length and shore area have the same tendency,indicating a fast growth in upper shoal,a moderate growth in lower shoal and a slow growth in middle shoal.In addition,the fractal property of the Jiuduansha Island is evident,with high values of goodness-of-fit.The fractal dimension of the whole Jiuduansha Island was growing from 2001 to 2008,and the fractal dimensions of upper and middle shoals are less than the dimension of the whole Jiuduansha,whereas the fractal dimension of lower shoal is larger than that of the whole Jiuduansha.