遥感中轴线法在江苏辐射沙洲潮沟演变监测中的应用

根据1988～2008 年的4 景TM 影像, 对江苏辐射沙洲地区5 条主要潮沟的动态演变研究方法进行了探讨。针对潮沟的特殊地形和复杂多变情况, 引入数学中的中轴线概念, 提出了遥感中轴线法, 通过中轴线位置的变化定量地表述潮沟演变。根据GIS 中Voronoi 图(V 图)的特性, 将中轴线的求取转换成V 图的生成过程, 用ArcGIS 软件实现, 将传统的目视解译方法改进为自动提取, 提取不同时相影像中轴主轴。研究结果表明: (1)用遥感中轴线法对不同时期的大型潮沟进行分析, 可较快、较准确地揭示潮沟的动态演变; (2)比较1988～2008 年的潮沟轴线, 西洋深槽变化最大, 西岸蚀退、东岸东移; 其他4 条潮沟均在南北方向上做往复摆动, 且逐渐趋于平缓。中轴线法可以实现对潮沟动态演变快速、准确地监测以及为整个辐射沙洲的开发建设提供理论基础。

Application of remote sensing medial axis method in investigation of dynamic changes of tidal creeks in radial sandbanks offshore Jiangsu Province

The coast of Jiangsu Province is famous for its radial sandbanks offshore. Dynamic changes of tidal creeks are difficult to survey for complex, quick-changing terrain. Medial axis methods of tidal creeks are the focus of this paper. The concept of medial axis in mathematics, as well as voronoi diagram (V diagram) in GIS for its special properties, was introduced and discussed,. Points in every edge of V diagram have the shortest distance to adjacent edges of polygon. Thus, medial axis extraction is converted to V diagram generation. Remote Sensing Medial Axis method (RSMA method) is presented because it is quick and convenient for survey, much better than previous traditional visual interpretation methods. Using the RSMA method, five main tidal creeks in the area were extracted and studied based on four TM images from 1988, 1995, 2003 and 2008. The results showed that: (1) for analysis on main tidal creeks in different time, RSMA method revealed the dynamic evolution quickly and accurately; (2) during the last 20 years, Xiyang deep trough had the greatest changes as the west coast retreated back and the east extended east; while the rest four tidal creeks moved in the north-south direction periodically and went straight gradually. Therefore, study on the evolution of tidal creeks has great significance for monitoring the dynamic changes of tidal fiat, development and utilization of coastal zone and the construction of coastal engineering.