Study On Remote Sensing Inversion Method Of Inconstant Tidal Flats DEM

China has rich tidal flat resources, which provide broad space for the future development of coastal areas. Detailed understanding of the topography and its evolution law is objectively needed in the exploitation and protection of tidal flats. However, existing means of measurement used in the tidal flat elevation measurements are subject to various restrictions due to that the tidal flats are severely affected by natural and human activities. It is difficult to achieve ideal results with high temporal resolution, periodicity, and large-scale tidal flat elevation information. Based on this, this paper selects the Dongsha and Liangyuesha as study area, which are located in South Yellow Sea radial sand ridges, and establishes a inconstant tidal flat elevation inversion framework which apply to large-scale area. The main contents are listed as follows:(1) Tidal flats elevation inversion based on medium-low spatial resolution remote sensing images (low spatial resolution, high temporal resolution). On the basis of analyzing the applicability of medium-low resolution images, DEMs of tidal flats were built and validated based on original point cloud and filtered point cloud respectively. A discussion has been made on the matter of time span and tidal level uniformity to realize their influences to inversion accuracy.(2) Tidal flats elevation inversion based on medium spatial resolution remote sensing images (high spatial resolution, low temporal resolution). Focus on the analysis of annual inversion accuracy and the matter of multiple time span, so as to realize the advantages and disadvantages of medium resolution images when applied to tidal flats elevation inversion.(3) Tidal flats elevation inversion based on fusion data of medium and medium-low spatial resolution remote sensing images (high spatial resolution, high temporal resolution). In order to make full use of medium and medium-low resolution images, a point cloud fusion method of multiple spatial resolution has been proposed. Then analyzed and validated the method in different time spans, and conducted initial experiment of seasonal sediment change for tidal flats by using the fusion data.The results show that: MODIS images with high temporal resolution offers a large selection of tidal flat elevation inversion, the disadvantage of its spatial resolution can be made up by the point cloud filtering method that proposed by this paper. After filtering, the absolute mean error reduced to42.74cm from48.68cm under annual time span, and the vertical accuracy better than45cm can be obtained under the time span of3months. Further analysis indicated that the vertical accuracy was positively correlated with tidal level uniformity.②On the contrary, the medium resolution images with higher spatial resolution could support higher vertical accuracy and expression of more details of tidal flats. Vertical accuracy of39.52cm can be obtained under annual time span. But the application of medium spatial resolution image was largely limited by its lower temporal resolution. Analysis showed that the waterlines interpreted from medium resolution images were in a state of severe tension in10months or less. The point cloud fusion method proposed by this paper can effectively shorten the elevation inversion time span and improve the vertical accuracy. The fusion data possessed both high spatial resolution and high temporal resolution. Based on this method, the vertical accuracy better than50cm、45cm and40cm can be obtained under the time span of only1,3, and6months, which means that the method could support seasonal sediment change research within one year.