Improving the TanDEM-X Digital Elevation Model for flood modelling using flood extents from Synthetic Aperture Radar images
Improving the TanDEM-X Digital Elevation Model for flood modelling using flood extents from Synthetic Aperture Radar images
复制标题
DOI：
10.1016/j.rse.2015.11.018
复制
发表时间：
2016-02
影响因子：
13.5
通讯作者：
D. Mason;M. Trigg;J. García-Pintado;H. Cloke;J. Neal;P. Bates
中科院分区：
文献类型：
--
作者：
D. Mason;M. Trigg;J. García-Pintado;H. Cloke;J. Neal;P. Bates
发达国家的许多洪泛区的地形现在已经使用高分辨率传感器进行了调查，例如机载LiDAR（光探测和测距），提供了精确的数字高程模型（DEM），有助于精确的洪水淹没建模。对于发展中国家的偏远河流，情况并非总是如此。然而，在不久的将来，高分辨率TanDEM-X WorldDEM.In一个平行的发展，越来越多地使用洪水范围来自高分辨率合成孔径雷达（SAR）图像的校准，验证和同化观测到洪水淹没模型，以提高这些的DEM的精度，对这些河流的建模研究。本文讨论了SAR洪水范围的另一个用途，即提高洪水范围覆盖的洪泛区中TanDEM-X DEM的精度，从而永久性地改善该DEM，以用于未来的洪水建模和其他研究。该方法基于这样一个事实，即对于较大的河流，水位通常沿河段沿着变化缓慢，从而洪水范围的边界（水线）可以局部地被视为准等高线。因此，沿着水线的一小段沿着的相邻像素的高度可以被视为具有共同总体均值的样本。截面中中心像素的高度可以用这些高度的平均值代替，从而得到更准确的估计。虽然这将导致沿着水线的高度误差减小，但水线是二维空间中的线性特征。然而，也可以对相邻水线对之间的DEM高度进行改进，因为由一对中的较高水线包围的DEM高度必须至少不高于沿较高水线的校正高度沿着，而未由较低水线包围的DEM高度通常必须不低于沿较低水线的校正高度沿着。此外，DEM的高度之间的较高和较低的水线也可以分配较小的误差，因为减少了错误的校正水线heights.The方法进行了测试，一节的TanDEM-X中间DEM（IDEM），覆盖11公里的沃里克郡埃文，英格兰。在2012年11月洪水的不同阶段，提供了四幅COSMO-SKyMed图像的洪水范围，并提供了激光雷达数字高程模型以供验证。在洪水范围覆盖的区域，原始IDEM高度与相应的LiDAR高度的平均差为0.5 m，标准差为2.0 m，而校正高度的平均差为0.3 m，标准差为1.2 m。这些数据表明，使用该方法可以显着减少IDEM高度偏差和误差，校正误差仅为原始的60%。即使只使用洪峰附近的一幅SAR图像，校正误差也只有原始的66%。该方法还应能够改进TanDEM-X数字高程模型和其他数字高程模型的最终版本，并可用于SWOT（地表水和海洋地形）卫星的数据。
The topography of many floodplains in the developed world has now been surveyed with high resolution sensors such as airborne LiDAR (Light Detection and Ranging), giving accurate Digital Elevation Models (DEMs) that facilitate accurate flood inundation modelling. This is not always the case for remote rivers in developing countries. However, the accuracy of DEMs produced for modelling studies on such rivers should be enhanced in the near future by the high resolution TanDEM-X WorldDEM.In a parallel development, increasing use is now being made of flood extents derived from high resolution Synthetic Aperture Radar (SAR) images for calibrating, validating and assimilating observations into flood inundation models in order to improve these. This paper discusses an additional use of SAR flood extents, namely to improve the accuracy of the TanDEM-X DEM in the floodplain covered by the flood extents, thereby permanently improving this DEM for future flood modelling and other studies.The method is based on the fact that for larger rivers the water elevation generally changes only slowly along a reach, so that the boundary of the flood extent (the waterline) can be regarded locally as a quasi-contour. As a result, heights of adjacent pixels along a small section of waterline can be regarded as samples with a common population mean. The height of the central pixel in the section can be replaced with the average of these heights, leading to a more accurate estimate. While this will result in a reduction in the height errors along a waterline, the waterline is a linear feature in a two-dimensional space. However, improvements to the DEM heights between adjacent pairs of waterlines can also be made, because DEM heights enclosed by the higher waterline of a pair must be at least no higher than the corrected heights along the higher waterline, whereas DEM heights not enclosed by the lower waterline must in general be no lower than the corrected heights along the lower waterline. In addition, DEM heights between the higher and lower waterlines can also be assigned smaller errors because of the reduced errors on the corrected waterline heights.The method was tested on a section of the TanDEM-X Intermediate DEM (IDEM) covering an 11 km reach of the Warwickshire Avon, England. Flood extents from four COSMO-SKyMed images were available at various stages of a flood in November 2012, and a LiDAR DEM was available for validation. In the area covered by the flood extents, the original IDEM heights had a mean difference from the corresponding LiDAR heights of 0.5 m with a standard deviation of 2.0 m, while the corrected heights had a mean difference of 0.3 m with standard deviation 1.2 m. These figures show that significant reductions in IDEM height bias and error can be made using the method, with the corrected error being only 60% of the original. Even if only a single SAR image obtained near the peak of the flood was used, the corrected error was only 66% of the original. The method should also be capable of improving the final TanDEM-X DEM and other DEMs, and may also be of use with data from the SWOT (Surface Water and Ocean Topography) satellite.