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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Accounting for uncertainty in DEMs from repeat topographic surveys: improved sediment budgets
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Accounting for uncertainty in DEMs from repeat topographic surveys: improved sediment budgets

机译：重复地形调查中DEM的不确定性说明：改进的沉积物预算

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摘要

Repeat topographic surveys are increasingly becoming more affordable, and possible at higher spatial resolutions and over greater spatial extents. Digital elevation models (DEMs) built from such surveys can be used to produce DEM of Difference (DoD) maps and estimate the net change in storage terms for morphological sediment budgets. While these products are extremely useful for monitoring and geomorphic interpretation, data and model uncertainties render them prone to misinterpretation. Two new methods are presented, which allow for more robust and spatially variable estimation of DEM uncertainties and propagate these forward to evaluate the consequences for estimates of geomorphic change. The fi rst relies on a fuzzy inference system to estimate the spatial variability of elevation uncertainty in individual DEMs while the second approach modifi es this estimate on the basis of the spatial coherence of erosion and deposition units. Both techniques allow for probabilistic representation of uncertainty on a cell-by-cell basis and thresholding of the sediment budget at a user-specifi ed confi dence interval. The application of these new techniques is illustrated with 5 years of high resolution survey data from a 1 km long braided reach of the River Feshie in the Highlands of Scotland. The reach was found to be consistently degradational, with between 570 and 1970 m3 of net erosion per annum, despite the fact that spatially, deposition covered more surface area than erosion. In the two wetter periods with extensive braid-plain inundation, the uncertainty analysis thresholded at a 95% confi dence interval resulted in a larger percentage (57% for 2004–2005 and 59% for 2006–2007) of volumetric change being excluded from the budget than the drier years (24% for 2003–2004 and 31% for 2005–2006). For these data, the new uncertainty analysis is generally more conservative volumetrically than a standard spatially-uniform minimum level of detection analysis, but also produces more plausible and physically meaningful results. The tools are packaged in a wizard-driven Matlab software application available for download with this paper, and can be calibrated and extended for application to any topographic point cloud (x,y,z).
机译：重复进行地形调查变得越来越负担得起，并且有可能在更高的空间分辨率和更大的空间范围内进行。通过这种调查建立的数字高程模型（DEM）可用于生成差异DEM（DoD）图，并估计形态沉积物预算的存储项的净变化。尽管这些产品对于监视和地貌解释极为有用，但数据和模型的不确定性使它们易于产生错误解释。提出了两种新方法，它们允许对DEM不确定性进行更鲁棒的和空间可变的估计，并将其向前传播以评估对地貌变化的估计结果。第一种方法是依靠模糊推理系统来估计各个DEM中高程不确定性的空间变异性，而第二种方法是根据侵蚀和沉积单元的空间相干性修改这种估计。两种技术都可以在每个单元格的基础上概率性表示不确定性，并可以在用户指定的置信区间内确定沉积物预算的阈值。来自苏格兰高地费希河1公里长辫状河段的5年高分辨率调查数据说明了这些新技术的应用。尽管在空间上沉积物覆盖的面积比侵蚀覆盖的面积大，但据发现该河段一直在退化，每年发生570至1970 m3的净侵蚀。在两个辫状平原泛滥的较湿润时期，不确定性分析以95％的置信区间为阈值，导致更大的百分比（2004-2005年为57％，2006-2007年为59％）被排除在外。预算比较干旱的年份（2003-2004年为24％，2005-2006年为31％）。对于这些数据，新的不确定性分析在体积上通常比标准的空间均匀性最小检测分析级别更为保守，但还会产生更合理和更有意义的结果。这些工具打包在向导驱动的Matlab软件应用程序中，可从本文中下载该工具，并可以对其进行校准和扩展以应用于任何地形点云（x，y，z）。

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