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.

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 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 cosmogenic nuclide results.

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.

Extraction and Analysis of Gully Head of Loess Plateau in China Based on Digital Elevation Model

In China′s Loess Plateau area, gully head is the most active zone of a drainage system in gully areas. The differentiation of loess gully head follows geospatial patterns and reflects the process of the loess landform development and evolution of its drainage system to some extent. In this study, the geomorphic meaning, basic characteristics, morphological structure and the basic types of loess gully heads were systematically analysed. Then, the loess gully head′s conceptual model was established, and an extraction method based on Digital Elevation Model(DEM) for loess gully head features and elements was proposed. Through analysing the achieved statistics of loess gully head features, loess gully heads have apparently similar and different characteristics depending on the different loess landforms where they are found. The loess head characteristics reflect their growth period and evolution tendency to a certain degree, and they indirectly represent evolutionary mechanisms. In addition, the loess gully developmental stages and the evolutionary processes can be deduced by using loess gully head characteristics. This study is of great significance for development and improvement of the theoretical system for describing loess gully landforms.

Comparative study and error analysis of digital elevation model interpolations

Researchers in P.R.China commonly create triangulate irregular networks(TINs) from contours and then convert TINs into digital elevation models(DEMs).However,the DEM produced by this method can not precisely describe and simulate key hydrological features such as rivers and drainage borders.Taking a hilly region in southwestern China as a research area and using ArcGISTM software,we analyzed the errors of different interpolations to obtain distributions of the errors and precisions of different algorithms and to provide references for DEM productions.The results show that different interpolation errors satisfy normal distributions,and large error exists near the structure line of the terrain.Furthermore,the results also show that the precision of a DEM interpolated with the Australian National University digital elevation model(ANUDEM) is higher than that interpolated with TIN.The DEM interpolated with TIN is acceptable for generating DEMs in the hilly region of southwestern China.

Facets of Uncertainty in Digital Elevation and Slope Modeling

This paper investigates the differences that result from applying different approaches to uncertainty modeling and reports an experimental examining error estimation and propagation in elevation and slope, with the latter derived from the former. It is confirmed that significant differences exist between uncertainty descriptors, and propagation of uncertainty to end products is immensely affected by the specification of source uncertainty.

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.

The J_2 invariant relative configuration of spaceborne SAR interferometer for digital elevation measurement

A 3-craft formation configuration is proposed to perform the digital elevation model （DEM） for the distributed spacebome interferometric synthetic aperture radar （InSAR）, and it is optimized by the modified ant colony algorithm to have the best compatibility with J2 invariant orbits created by differential correction algorithm. The configuration has succeeded in assigning the across-track baseline to vary periodically and with its mean value equal to the optimal baseline determined by the relative height measurement accuracy. The required relationship between crafts＇ magnitudes and phases is formulated for the general case of interferometry measure from non-orthographic and non-lateral view. The J2 invariant configurations created by differential correction algorithm are employed to investigate their compatibility with the required configuration. The colony algorithm is applied to search the optimal configuration holding the near-constant across-track baseline under the J2 perturbation, and the absolute height measurement accuracy is preferable as expected.

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.

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。

Digitally Mapping the Hydro-Topographical Context for Community Planning: A Case Study for the Upper Choapa River Watershed in Chile

Urban and non-urban settlements in many regions are usually located on the lands bordering shores, rivers, canals or streams. However, housing complexes, landfills, and areas for agriculture and mining are often assigned to locations without sufficiently detailed hydrographic information about subsequent potential if not actual flow and flooding impacts. Yet, for sustainable community planning with emphasis on harmonizing social, economic, environmental and institutional aspects, such information is essential. This article demonstrates how this need can in part be accommodated by way of digital elevation and wet-area modelling and mapping using the upper component of the Choapa watershed in Chile as a case study. The terrain of this area has sharply incised valleys, with communities, fields and roads strung narrowly along the Choapa River and its tributaries. Above these locations along the Estero de Los Pelambres near the Chile-Argentina border are major mining and mineral refining activities. This article provides modelling and mapping details about the wet-to-moist area zonation along the upper Choapa River valleys, and addresses some of the mining-induced changes from 2000 to 2010.

基于多尺度DEM一体化融合技术构建水利枢纽三维地形技术研究与应用

本文通过研究多尺度DEM一体化融合技术,构建了水利枢纽的三维地形模型,并深入研究了该技术在数字孪生乌鲁瓦提水利工程汛期模拟、汛期预演、汛期预警中的应用。首先对不同尺度DEM数据进行预处理,如数据清洗和去噪,以提高数据质量,然后采用多尺度分析方法,将不同尺度的DEM数据进行一体化融合,得到更准确、全面的地形信息。该技术的核心是基于多分辨率频域融合方法,将高分辨率DEM数据与低分辨率的DEM数据结合起来。通过分析不同尺度上的地形特征,可以提取出更丰富的地貌信息,为水利工程的规划和设计提供了重要的参考依据。

基于MAPGIS的DEM制作技术研究

结合具体的项目工程,主要以MAPGIS软件对DEM制作的过程和遇到的技术问题进行了探讨研究,比较分析了不同数据转换方式的差异,有效地实现了从DGN格式数据到最终DEM的生成,并在制作过程中优化了数据流程.

融合自注意力机制与生成对抗网络的DEM空洞填充

针对现有数字高程模型(digital elevation model, DEM)数据空洞填充算法存在修复效果不连续、适用空值范围狭小以及细节重构丢失等问题,提出了一种融合自注意力机制的生成式对抗网络的DEM空洞填充方法。首先,构造自注意力机制提取DEM数据特征信息,改善DEM空洞填充结果高程值不连续和纹理细节缺失的问题。其次,在生成器中使用对称结构的卷积与反卷积网络结构,保证生成可靠度较高的数据以实现空洞区域填充,并利用判别器实现空洞填充结果的预分类。最后,结合重构损失函数进行训练,提升DEM空洞填充结果对异常值的鲁棒性,增强模型的回归能力。采用不同分辨率DEM数据进行空洞填充并与现有方法进行对比,结果表明:所提方法能够大幅提升填充精度,有效解决原始数据中存在的空洞问题。

An Object-based Approach for Two-level Gully Feature Mapping Using High-resolution DEM and Imagery： A Case Study on Hilly Loess Plateau Region, China

Gully feature mapping is an indispensable prerequisite for the motioning and control of gully erosion which is a widespread natural hazard. The increasing availability of high-resolution Digital Elevation Model(DEM) and remote sensing imagery, combined with developed object-based methods enables automatic gully feature mapping. But still few studies have specifically focused on gully feature mapping on different scales. In this study, an object-based approach to two-level gully feature mapping, including gully-affected areas and bank gullies, was developed and tested on 1-m DEM and Worldview-3 imagery of a catchment in the Chinese Loess Plateau. The methodology includes a sequence of data preparation, image segmentation, metric calculation, and random forest based classification. The results of the two-level mapping were based on a random forest model after investigating the effects of feature selection and class-imbalance problem. Results show that the segmentation strategy adopted in this paper which considers the topographic information and optimal parameter combination can improve the segmentation results. The distribution of the gully-affected area is closely related to topographic information, however, the spectral features are more dominant for bank gully mapping. The highest overall accuracy of the gully-affected area mapping was 93.06% with four topographic features. The highest overall accuracy of bank gully mapping is 78.5% when all features are adopted. The proposed approach is a creditable option for hierarchical mapping of gully feature information, which is suitable for the application in hily Loess Plateau region.

Designing Thought,Technical Line and Some Theoretical Issues on Geospatial Digital Framework of China

Based on the developing tendency of present China’s basic GIS,this paper discusses the designing idea for scales of 1∶10 000,1∶50 000, 1∶250 000 and 1∶1 000 000 pyramid_like multi_layer and multi_resolution of the basic GIS.A technical line for the construction of basic GIS of the whole country and various provinces for sustainable development is put forward.And some important theoretical GIS issues touched by the technical process are discussed.

Evaluation and Validation of Recent Freely-Available ASTER-GDEM V.2, SRTM V.4.1 and the DEM Derived from Topographical Map over SW Grombalia (Test Area) in North East of Tunisia

Digital Elevation Models (DEMs) provide one of the most useful digital datasets for a wide range of users. Both the Shuttle Radar Topographic Mission (STRM V.4.1) topography and the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER-GDEM V.2) have been widely used in geomorphology, hydrology, tectonic, and others since they were made access to the public. The magnitude of vertical errors of two near-global DEMs—SRTM and ASTER-GDEM is compared and validated against a reference DEM which has a relatively high precision of 1:25,000 scale constructed from topographical map. Moreover, the reference DEM, ASTER-GDEM and SRTM were used as basic topographic data to extract some Morphometric index. The parameters like slope and shaded reflectance maps, were derived from the elevation distribution to provide a more sensitive indication of DEM quality. A square area in the North East of Tunisia was selected as a case study to test and evaluate the elevation accuracy of ASTER-GDEM and SRTM. The relative accuracy approach and absolute accuracy were adopted to evaluate global DEMs. The comparisons show that SRTM overestimates and ASTER-GDEM underestimates elevations, both DEMs can be used to extract the elevations of required geometric data,?i.e.?sub watershed boundaries, drainage information and cross sections. However, small errors still exist in. The lower root mean square errors values indicate that SRTM is comparatively more accurate than ASTER-GDEM.

arcPycor:an open-source automated GIS tool to co-register elevation datasets

Subtraction of elevation datasets(e.g.digital elevation models(DEMs)and non-continuous elevation points)acquired at different times is a useful method to monitor landform surface change.Due to heavy post-processing of these elevation datasets,multi-source errors are introduced into the resulting elevation data products.To improve the estimation of elevation change,co-registration of elevation datasets is a prerequisite.This paper presents an open-source automated GIS tool(arc Pycor)for co-registering elevation datasets.arc Pycor is coded in Python 2.7 and is run via Arc GIS for Desktop.The performances of arc Pycor have been evaluated using a series of experiments.In benchmark tests,the resolved co-registration vectors of arc Pycor are compared to the predefined shift vectors obtained by artificially misaligning the slave DEMs from the master elevation datasets.Results show that arc Pycor is able to co-register DEMs with relative high accuracy and can well align slave DEMs to non-continuous elevation points,which indicates its robustness in co-registering of elevation datasets.arc Pycor is also able to co-register multi-sourced DEMs of different resolutions in mountain areas.

基于DEM数据和遗传算法的对海雷达部署优化研究

针对当前雷达组网部署优化问题缺少对海探测研究,以及基于实际地形数据的遗传算法(GA)求解复杂度高的问题,开展了基于数字高程模型(DEM)数据和遗传算法的对海探测部署优化研究。基于预先阵地和对海探测雷达威力模型,所提的算法可有效减少遗传算法寻优空间,极大提高优化求解速度。仿真表明,该算法可获得和遍历法近似的最优结果,随着部署规模的增大,具有明显的速度优势。