Performance validation of High Mountain Asia 8-meter Digital Elevation Model using ICESat-2 geolocated photons

High Mountain Asia(HMA),recognized as a third pole,needs regular and intense studies as it is susceptible to climate change.An accurate and high-resolution Digital Elevation Model(DEM)for this region enables us to analyze it in a 3D environment and understand its intricate role as the Water Tower of Asia.The science teams of NASA realized an 8-m DEM using satellite stereo imagery for HMA,termed HMA 8-m DEM.In this research,we assessed the vertical accuracy of HMA 8-m DEM using reference elevations from ICESat-2 geolocated photons at three test sites of varied topography and land covers.Inferences were made from statistical quantifiers and elevation profiles.For the world’s highest mountain,Mount Everest,and its surroundings,Root Mean Squared Error(RMSE)and Mean Absolute Error(MAE)resulted in 1.94 m and 1.66 m,respectively;however,a uniform positive bias observed in the elevation profiles indicates the seasonal snow cover change will dent the accurate estimation of the elevation in this sort of test sites.The second test site containing gentle slopes with forest patches has exhibited the Digital Surface Model(DSM)features with RMSE and MAE of 0.58 m and 0.52 m,respectively.The third test site,situated in the Zanda County of the Qinghai-Tibet,is a relatively flat terrain bed,mostly bare earth with sudden river cuts,and has minimal errors with RMSE and MAE of 0.32 m and 0.29 m,respectively,and with a negligible bias.Additionally,in one more test site,the feasibility of detecting the glacial lakes was tested,which resulted in exhibiting a flat surface over the surface of the lakes,indicating the potential of HMA 8-m DEM for deriving the hydrological parameters.The results accrued in this investigation confirm that the HMA 8-m DEM has the best vertical accuracy and should be of high use for analyzing natural hazards and monitoring glacier surfaces.

基于DEM的雷达阵地选址预处理方法研究

防空预警雷达阵地选址的优劣直接影响雷达本身及防空武器作战效能的发挥.针对基于数字高程模型(DEM)的常规实时计算方法存在耗时、耗力的问题,在明确阵地选址预处理内容的基础上,提出了预处理的具体流程和参数计算方法.通过数据预处理,以空间换时间的方式解决了阵地自动选址计算量大、耗时长的问题.实例仿真结果表明,该雷达阵地选址预处理方法大大缩短了自动选址时间,有效提高了选址效率.

基于机载多角度InSAR技术的复杂地形高精度DEM重建方法

干涉合成孔径雷达(Interferomtric Synthetic Aperture Radar,InSAR)是全天时、全天候获取三维地表信息重要的技术手段。机载InSAR系统具有机动灵活、多角度获取数据的优势,可以高效率、高精度获取数字高程模型(Digital Elevation Model,DEM)数据。但是,在地形复杂区域,InSAR侧视成像易在地形陡峭区域形成较大范围的阴影和严重的叠掩现象,阴影和叠掩区域在SAR图像上体现为信息的丢失,从而导致DEM数据大面积无效数据的存在,严重影响DEM数据的质量及应用。针对这一问题,本文提出了基于机载多角度InSAR技术的复杂地形高精度DEM重建方法,基于考虑地形起伏的机载多角度InSAR数据获取任务规划设计,最大程度的避免阴影和叠掩导致的无效数据;基于高精度InSAR数据处理,保证每个角度DEM数据精度的高度一致性;基于快速多角度DSM数据融合与滤波处理,实现多角度InSAR体制复杂地形DEM高精度重建。本文以四川省西部山区大坡度、非连续等复杂地形为例,基于本文提出的方法,利用3个角度InSAR数据融合处理,生成了高精度DEM数据,试验结果表明,本文提出的方法获取复杂地形DEM数据高程均方根误差为0.6 m,同时,数据有效率大于99%。

基于三元DEM的露天煤矿封闭壳状包络体素建模研究

传统地质模型受自身结构性质和布尔运算效率的局限,限制了采矿模型的生成,无法满足露天矿大规模物料规划问题的需求。针对上述问题,对开采体块段模型及采矿模型进行了定义,并提出了一种基于三元DEM的露天煤矿封闭壳状包络体素快速建模方法,即煤岩模型的顶面、底面和侧面DEM建模,三元DEM经固化后即可生成煤岩体对应的封闭壳状包络体素模型。该模型介于实体模型和块体模型之间,能够保障算量精度,同时具有较高的布尔运算效率,可以现实定点、定向的尺寸和结构剖切,在传统算量地模的基础上,通过特定的结构定义,丰富剥采程序和工艺参数等技术指标属性,定制专属的采矿模型,更好地服务于露天矿物料流规划、采剥生产计划动态优化等问题。

Effect of digital elevation models on monitoring slope displacements in open-pit mine by differential interferometry synthetic aperture radar

Displacement monitoring in open-pit mines is one of the important tasks for safe management of mining processes.Differential interferometric synthetic aperture radar(DInSAR),mounted on an artificial satellite,has the potential to be a cost-effective method for monitoring surface displacements over extensive areas,such as open-pit mines.DInSAR requires the ground surface elevation data in the process of its analysis as a digital elevation model(DEM).However,since the topography of the ground surface in open-pit mines changes largely due to excavations,measurement errors can occur due to insufficient information on the elevation of mining areas.In this paper,effect of different elevation models on the accuracy of the displacement monitoring results by DInSAR is investigated at a limestone quarry.In addition,validity of the DInSAR results using an appropriate DEM is examined by comparing them with the results obtained by global positioning system(GPS)monitoring conducted for three years at the same limestone quarry.It is found that the uncertainty of DEMs induces large errors in the displacement monitoring results if the baseline length of the satellites between the master and the slave data is longer than a few hundred meters.Comparing the monitoring results of DInSAR and GPS,the root mean square error(RMSE)of the discrepancy between the two sets of results is less than 10 mm if an appropriate DEM,considering the excavation processes,is used.It is proven that DInSAR can be applied for monitoring the displacements of mine slopes with centimeter-level accuracy.

Determining topographic shielding from digital elevation models for cosmogenic nuclide analysis: a GIS model for discrete sample sites

Topographic shielding(TS) is an important factor in cosmogenic nuclide surface exposure dating. The development of geographic information systems(GIS) and the availability of digital elevation models(DEMs) make it possible to derive this factor directly from a DEM. Most available GIS models derive the TS factors for an area(all cells in a DEM) without the consideration of surface conditions of individual sites, such as the strike, dip,and height above ground, into the calculation. This paper presents a new GIS model to derive the TS factors for discrete sample sites. This model uses the Skyline and Skyline Graph functions in ArcGIS to extract the set of azimuth and elevation angles of topographic obstructions around each site from a DEM(considering the sample height above ground)and then incorporates the strike and dip information of the sample surface to derive the TS factor. All processing tools and steps are streamlined in ArcGIS modelbuilder and this model can be run like a standard ArcGIS geoprocessing tool. It provides an easy and user-friendly means to derive the TS factors for discrete samples based on a DEM and the measured strike, dip and sample height for each site.

Determining Topographic Shielding from Digital Elevation Models for Cosmogenic Nuclide Analysis:a GIS Approach and Field Validation

Topographic shielding of cosmic radiation flux is a key parameter in using cosmogenic nuclides to determine surface exposure ages or erosion rates. Traditionally, this parameter is measured in the field and uncertainty and/or inconsistency may exist among different investigators. This paper provides an ArcGIS python code to determine topographic shielding factors using digital elevation models （DEMs）. This code can be imported into ArcGIS as a geoprocessing tool with a user-friendly graphical interface. The DEM-derived parameters using this method were validated with field measurements in central Tian Shan. Results indicate that DEM-derived shielding factors are consistent with field-measured values. It provides a valuable tool to save fieldwork efforts and has the potential to provide consistent results for different regions in the world to facilitate the comparison of cosmogenie nuclide results.

基于ICESat-2的横断山区NASA DEM高程精度评价与误差校正

以星载激光雷达ICESat–2为参考数据源,将NASA DEM作为实验数据,分析了其在横断山区中西部复杂地形地貌区的整体高程精度;同时,研究了DEM误差与地表变量(如坡度、坡向、起伏度、植被覆盖度、土地利用类型等)之间的关系。为校正NASA DEM的高程误差,引入随机森林、反向传播神经网络、极度梯度提升树模型和轻量级梯度提升模型等4种机器学习方法,结合地表变量构建了高程误差校正模型并对校正后的NASA DEM进行精度分析。结果表明:NASA DEM的高程平均误差为–3.5 m,平均绝对误差为8.2 m,均方根误差为11.7 m,高程误差符合正态分布。NASA DEM的高程精度随着坡度、起伏度和植被覆盖度的增大而降低,不同坡向和土地利用类型下的高程精度存在较大差异。4种机器学习模型均能校正NASA DEM的高程精度,校正后的平均误差、平均绝对误差和均方根误差均有所改善;RF、XGBoost和LightGBM校正后的平均误差均为0 m;BPNN校正后平均绝对误差最低为6.9 m;BPNN和XGBoost校正后均方根误差最低均为10.6 m;BPNN校正后的R2值最高;BPNN在不同土地利用类型下的校正精度表现最佳。本研究结果为地学研究中选择和应用NASA DEM时提供精度上的参考依据,并通过引入多种机器学习模型,为NASA DEM及其他全球DEM产品高程误差校正研究提供了有效的方法论。

DEM数据坐标转换和成果质量的检查方法

针对数字高程模型(DEM)数据三维坐标转换和转换成果质量检查的需求,本文研究了基于阿尔克·吉斯(ArcGIS)开发引擎平台的DEM数据的平面和高程坐标转换技术方法;同时根据DEM数据本身的特点,研究确定了合理的DEM数据转换成果质量检查内容和指标,解决了DEM数据转换成果质量检查标准的实际生产应用问题。本项目研究成果可保障北京市DEM数据在统一的基准下应用,推动与测绘地理信息相关的规划、建设和管理工作。

Curvature derived from LiDAR digital elevation models as simple indicators of debris-flow susceptibility

To mitigate the damage caused by debris flows resulting from heavy precipitation and to aid in evacuation plan preparation, areas at risk should be mapped on a scale appropriate for affected individuals and communities. We tested the effectiveness of simply identifying debris-flow hazards through automated derivation of surface curvatures using LiDAR digital elevation models. We achieved useful correspondence between plan curvatures and areas of existing debris-flow damage in two localities in Japan using the analysis of digital elevation models(DEMs). We found that plan curvatures derived from 10 m DEMs may be useful to indicate areas that are susceptible to debris flow in mountainous areas. In residential areas located on gentle sloping debris flow fans, the greatest damage to houses was found to be located in the elongated depressions that are connected to mountain stream valleys. Plan curvaturederived from 5 m DEM was the most sensitive indicators for susceptibility to debris flows.

Uncertainty of Slope Length Derived from Digital Elevation Models of the Loess Plateau, China

Although many studies have investigated slope gradient uncertainty derived from Digital Elevation Models(DEMs), the research concerning slope length uncertainty is far from mature. This discrepancy affects the availability and accuracy of soil erosion as well as hydrological modeling. This study investigates the formation and distribution of existing errors and uncertainties in slope length derivation based on 5-m resolution DEMs of the Loess Plateau in the middle of China. The slope length accuracy in three different landform areas is examined to analyse algorithm effects. The experiments indicate that the accuracy of the flat test area is lower than that of the rougher areas. The value from the specific contributing area(SCA) method is greater than the cumulative slope length(CSL), and the differences between these two methods arise from the shape of the upslope area. The variation of mean slope length derived from various DEM resolutions and landforms. The slope length accuracy decreases with increasing grid size and terrain complexity at the six test sites. A regression model is built to express the relationship of mean slope length with DEM resolution less than 85 m and terrain complexity represented by gully density. The results support the understanding of the slope length accuracy, thereby aiding in the effective evaluation of the modeling effect of surface process.

Managing Soil Erosion Potential by Integrating Digital Elevation Models with the Southern China's Revised Universal Soil Loss Equation——A Case Study for the West Lake Scenic Spots Area of Hangzhou,China

In China, many scenic and tourism areas are suffering from the urbanization that results from physical development of tourism projects, leading to the removal of the vegetative cover, the creation of areas impermeable to water, in-stream modifications, and other problems. In this paper, the risk of soil erosion and its ecological risks in the West Lake Scenic Spots （WLSS） area were quantitatively evaluated by integrating the revised universal soil loss equation （RUSLE） with a digital elevation model （DEM） and geographical information system （GIS） software. The standard RUSLE factors were modified to account for local climatic and topographic characteristics reflected in the DEM maps, and for the soil types and vegetation cover types. An interface was created between the Areinfo software and RUSLE so that the level of soil erosion and its ecological risk in the WLSS area could be mapped immediately once the model factors were defined for the area. The results from an analysis using the Areinfo-RUSLE interface showed that the risk value in 93 % of the expanding western part of the WLSS area was moderate or more severe and the soil erosion risk in this area was thus large compared with that in the rest of the area. This paper mainly aimed to increase the awareness of the soil erosion risk in urbanizing areas and suggest that the local governments should consider the probable ecological risk resulting from soil erosion when enlarging and developing tourism areas.

Beach Morphology and Sediment Budget Variability Based on High Quality Digital Elevation Models Derived from Field Data Sets

The morphological and volumetric changes of a sandy beach were investigated through a series of two- monthly filed surveys carried out aver a 2-year period from April 2005 to January 2007. This paper discuss the ability of 3-D digital elevation models (DEMs) derived from high accurate data to assess and quantify beach morphodynamics in relation with wave forcing. The methodology and data acquisition are described and consist mainly in the production of interpolated DEMs from which a variety of representations can be made, including as elevation change maps, two-dimensional cross-sections of the beach, calculation of net volume. The results of the analysis highlight seasonal changes in beach morphology due to variations in wave energy. This behavior is characterized by beach erosion and bar decay under high-energy waves and net accretion and bar formation during relatively fair weather conditions. The sand budgets adjustments show that the loss of volume in the winter months is compensated for by accumulation to the beach during summer. This trend suggests that there is a mechanism which controls the beach evolution. The correlation between beach changes and wave energy variations highlights a net relation between them. The results from this in- vestigation state the value of DEMs utilized and demonstrate the efficiency of the 3-D approach employed here to assess the erosion and accretion patterns which would not be visualized using 2-D profiles.

基于DEM地形特征因子的海原断裂带中东段构造活动性分析

海原断裂带是中国西北地区重要的活动断裂带,也是青藏高原东北边界的重要组成部分。海原断裂带活动性研究对深入了解青藏高原东北缘构造格局和第四纪构造地貌具有重要意义,对于地质灾害预测和地质风险评估也有很大的参考作用。本次研究基于数字高程模型(DEM)数据,利用ArcGIS软件对该段各流域的地貌参数进行提取计算,定量获得该段各流域的地貌形态特征,最后对研究区的相对构造活动性程度进行分析。面积-高程积分(HI)表明断裂带两侧的地形梯度差异显著,断裂带及其南侧盆地坡度更大,山地更陡峭,地貌侵蚀作用也更强。流域盆地不对称度(AF)表明研究区内海原断裂带中东段由西至东发生掀斜的程度越来越小,流域盆地的形态也从不对称向对称变化。盆地延伸率(Re)则显示断裂北侧盆地的狭长程度要明显高于断裂南侧,但更倾向于由于早期构造活动或者地壳停止运动后的缓慢调整和变形造成。标准化坡降指数(SL)结果显示断裂带南侧河流坡降较大,北侧则较小;经过断裂的流域SL值中,王滩-黄鼠滩段(西段)明显要高于其他段,表明此段的地貌演化的活跃程度明显更高。地震活动则显示断裂东段地震更为密集,但西段受哈斯山段复杂的断层-褶皱系统影响较大,因此综合地形特征因子的分析结果,可以推断海原断裂带中东段存在断裂活动性差异。南侧地形陡峭、起伏较大且河流发育良好,表明该区域可能存在较活跃的构造活动,而北侧地形相对平缓、河流发育较弱以及较小的坡降指数,则表明该区域可能存在较弱的构造活动。

基于倾斜模型的DEM数据生产方法研究

随着倾斜摄影测量技术发展和无人机设备的日益先进,全国有较多县、市实现了倾斜模型全域覆盖;数字高程模型(DEM)可用于研究和分析地形、水系流域、地物识别等,是重要的基础地理信息数据。阐述了基于原始倾斜模型的DEM数据生产方法,并使用实测RTK点验证数据精度,证明基于原始模型生产DEM数据的可行性。

结合潮位与DEM的红树林遥感识别研究

以广西北部湾为研究区,针对潮位周期性变化导致稀疏低矮红树林难以被准确提取的问题,基于多潮位Landsat8 OLI图像和数字高程模型(DEM)数据,通过构建红树林识别决策树模型,并以支持向量机(SVM)为对照,评价结合潮位和DEM信息的决策树法提取红树林信息的可行性.研究结果表明:1)不同高度、不同密度以及不同潮位红树林之间光谱差异均较大,稀疏低矮红树林也与阴坡林地、水体-陆生植被混合像元光谱存在严重“异物同谱”效应;2)无论是基于低潮位、高潮位图像,还是多潮位图像,相比未区分高度和密度,在SVM中将细分为高密红树林和稀矮红树林,其总体精度(分为红树林和非红树林两类)可分别提高4.65、4.41和7.22个百分点;3)基于多潮位图像及DEM的决策树模型识别的总体精度和Kappa系数分别为98.80%和0.973,比SVM中最佳值分别高出1.62个百分点和0.035.因此,通过同时考虑红树林高度、密度、潮位和DEM等特征,可明显提高红树林遥感识别的精度.

基于ASTER GDEM的黑龙江省地形起伏度分析

地形起伏度是描述地貌形态的重要指标,反映了研究区域内地势起伏特征。以黑龙江省为研究区域、以30 m分辨率的ASTER GDEM(先进星载热发射和反射辐射仪全球数字高程模型)数据为基础,在ArcGIS平台上利用领域分析法分析不同窗口大小下的地形起伏度,通过均值变点法得出最佳统计单元面积为0.396 9 km^(2)。在此基础上对黑龙江省地势起伏度进行分析。结果表明黑龙江省地形起伏可分为4类,主要以台地、丘陵为主,平原占比次之。

LAN Tool: A GIS Tool for the Improvement of Digital Elevation Models Using Drainage Network Attributes

Digital Elevation Models (DEMs) are constructed using altitude point data and various interpolation techniques. The quality and accuracy of DEMs depend on data point density and the interpolation technique used. Usually however, altitude point data especially in plain areas do not provide realistic DEMs, mainly due to errors produced as a result of the interpolation technique, resulting in imprecise topographic representation of the landscape. Such inconsistencies, which are mainly in the form of surface depressions, are especially crucial when DEMs are used as input to hydrologic modeling for impact studies, as they have a negative impact on the model’s performance. This study presents a Geographical Information System (GIS) tool, named LAN (Line Attribute Network), for the improvement of DEM construction techniques and their spatial accuracy, using drainage network attributes. The developed tool does not alter the interpolation technique, but provides higher point density in areas where most DEM problems occur, such as lowland areas or places where artificial topographic features exist. Application of the LAN tool in two test sites showed that it provides considerable DEM improvement.

A COM-based Framework for Management,Analysis and Visualization of Large Scope Digital Elevation Models

This paper presents a component object model (COM) based framework for managing, analyzing and visualizing massive multi-scale digital elevation models (DEMs). The framework consists of a data management component (DMC), which is based on RDBMS/ORDBMS, a data analysis component (DAC) and a data render component (DRC). DMC can manage massive multi-scale data expressed at various reference frames within a pyramid database and can support fast access to data at variable resolution. DAC integrates many useful applied analytic functions whose results can be overlaid with the 3D scene rendered by DRC. DRC provides view-dependent data paging with the support of the underlying DMC and organizes the potential visible data at different levels into rendering.

基于数字高程模型(DEM)的溧阳天目湖地区地貌区划

江苏溧阳天目湖地区地貌单元的划分可以提升分区、分类型、分层次的地表基质调查效率。基于天目湖地区5 m分辨率的数字高程模型(DEM),应用GIS软件提取高程、坡度、地形起伏度信息;在提取地形起伏度的过程中运用邻域分析法与均值变点法,确定提取地形起伏度的最佳分析窗口大小为37×37像元。将地形起伏度、海拔高程及坡度3种地形要素进行空间叠加分析,并对地貌分布格局与差异变化进行初步探讨,提出将天目湖地区地貌指标划分为平原、河流阶地、山间谷地、台地、丘陵5种类型,其中以山间谷地与台地地貌为主,二者分别占32.97%、21.96%。划分结果符合天目湖地区地貌格局差异及空间分布,有效体现出天目湖地区平原向丘陵过渡的地貌特征,为后续开展地表基质的调查工作提供较为可靠的地理依据,对探究地貌分布格局与地表基质属性差异具有一定的意义。