A DEM CONSTRUCTION METHOD FOR INCONSTANT INTER-TIDAL ZONE BASE ON SHORT-INTERVAL, HIGH FREQUENCY MODIS DATA SET: A CASE STUDY IN THE DONGSHA SANDBANK OF THE JIANGSU RADIAL TIDAL SAND-RIDGES

摘要

Surface elevation is a critical data for geo-science study. As far as some regions with rapidly-changing in landform, analyzing the surface elevation of different periods help provide scientific basis for regional economic & social sustained development. Jiangsu coast is force tide zone, and the complicated sediment dynamical environment, gently rolling tidal-flat landform, huge spatial difference in tidal-flat moisture content changing with the time, geomorphic type and tidal condition, sediment concentration differing in sea area, season and tidal period. It is difficult to retrieve tidal-flat elevation information from RS imageries. Massive, high frequency and complete in temporal series of MODIS imageries on the study area since 2000 have been accumulated. The study takes Dongsha Sandbank as a case study area, and attempts to formulate a construction method for historical DEM based on short-interval, high frequency MODIS RS imageries data set. Starting point of the study is: shorelines of exposed tidal flat changes period with time because the tidal regime of research area is semi-diurnal tide. Contours of the sandbank in different RS imagery differ from each other due to the following factors: 1) Difference caused by spatial and temporal evolution of the sandbank itself. 2) Difference caused by the huge difference of tidal-level between different imaging moments. If the time interval is short enough, the factor of sandbank evolution can be ignored, and the leading difference of the sandbank shoreline in the two RS imageries reflects the influence of tidal-level difference. For this reason, DEM of the inter-tidal zone construction framework was discussed.