共查询到20条相似文献，搜索用时 15 毫秒
1.
DEM数据是流域水文分析和模拟的基础,不同DEM分辨率尺度深刻影响着水文分析和水文过程模拟的结果。本文基于机载LiDAR获取的DEM数据,分析了不同分辨率LiDAR DEM在坡度提取、水文指数分析和流域特征参数提取中的差异及产生原因;基于SWAT分布式水文模型模拟研究了不同分辨率DEM数据的水文效应。研究结果表明：随着DEM分辨率的降低,坡度平均值减小,TWI平均值增大,SPI平均值减小,LSF均值先增大后减小,当分辨率为10 m时,LSF取得最大值;SWAT模型模拟结果表明,随分辨率的降低、坡度值的变小,地形湿度指数变大,蒸散发量增加,地表径流深减小,而土壤渗漏量与地下径流量则是先减小后增加,出现极值时DEM分辨率为10 m,与LSF出现极值时一致。 相似文献
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Ikechukwu Nnamdi Maduako Raphael Ike Ndukwu Caleb Ifeanyichukwu Onyedika Igbokwe 《Journal of the Indian Society of Remote Sensing》2017,45(4):631-642
Soil moisture estimation from satellite earth observation has emerged effectively advantageous due to the high temporal resolution, spatial resolution, coverage, and processing convenience it affords. In this paper, we present a study carried out to estimate soil moisture level at every location within Enugu State Nigeria from satellite earth observation. Comparative analysis of multiple indices for soil moisture estimation was carried out with a view to evaluating the robustness, correlation, appropriateness and accuracy of the indices in estimating the spatial distribution of soil moisture level in Enugu State. Results were correlated and validated with In-Situ soil moisture observations from multi-sample points. To achieve this, the Topographic Wetness Index (TWI), based on digital elevation data, the Temperature Vegetation Dryness Index (TVDI) and an improved TVDI (iTVDI) incorporating air temperature and a Digital Elevation Model (DEM) were calculated from ASTER global DEM and Landsat images. Possible dependencies of the indices on land cover type, topography, and precipitation were explored. In-Situ soil moisture data were used to validate the derived indices. The results showed that there was a positive significant relationship between iTVDI versus TVDI (R = 0.53, P value < 0.05), while in iTVDI versus TWI (R = 0.00, P value > 0.05) and TVDI versus TWI (R = ?0.01, P value > 0.05) no significant relationship existed. There was a strong relationship between iTVDI and topography, land cover type, and precipitation than other indices (TVDI, TWI). In situ measured soil moisture values showed negative significant relationship with TVDI (R = ?0.52, P value < 0.05) and iTVDI (R = ?0.63, P value < 0.05) but not with TWI (R = ?0.10, P value > 0.05). The iTVDI outperformed the other two index; having a stronger relationship with topography, precipitation, land cover classes and soil moisture. It concludes that although iTVDI outperformed other indices (TVDI, TWI) in soil moisture estimation, the decision of which index to apply is dependent on available data, the intent of usage and spatial scale. 相似文献
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The automatic extraction of valley lines (VLs) from digital elevation models (DEMs) has had a long history in the GIS and hydrology fields. The quality of the extracted results relies on the geometrical shape, spatial tessellation, and placement of the grids in the DEM structure. The traditional DEM structure consists of square grids with an eight‐neighborhood relationship, where there is an inconsistent distance measurement between orthogonal neighborhoods and diagonal neighborhoods. The directional difference results in the extracted VLs by the D8 algorithm not guaranteeing isotropy characteristics. Alternatively, hexagonal grids have been proved to be advantageous over square grids due to their consistent connectivity, isotropy of local neighborhoods, higher symmetry, increased compactness, and more. Considering the merits above, this study develops an approach to VL extraction from DEMs based on hexagonal grids. First, the pre‐process phase contains the depression filling, flow direction calculation, and flow accumulation calculation based on the six‐neighborhood relationship. Then, the flow arcs are connected, followed by estimating the flow direction. Finally, the connected paths are organized into a tree structure. To explore the effectiveness of hexagonal grids, comparative experiments are implemented against traditional DEMs with square grids using three sample regions. By analyzing the results between these two grid structures via visual and quantitative comparison, we conclude that the hexagonal grid structure has an outstanding ability in maintaining the location accuracy and bending characteristics of extracted valley networks. That is to say, the DEM‐derived VLs based on hexagonal grids have better spatial agreement with mapped river systems and lower shape diversion under the same resolution representation. Therefore, the DEMs with hexagonal grids can extract finer valley networks with the same data volume relative to traditional DEM. 相似文献
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利用时序PS-InSAR监测青藏高原冻土区地表形变 总被引：1，自引：0，他引：1
多年冻土及其活动层的变化对研究全球气候变化和生物多样性具有重要意义.传统的冻土测量方法通常只针对特定地点,空间覆盖范围有限,尤其是青藏高原冻土.本文采用C波段Sentinel-1A IW模式数据并结合一种顾及永久散射体的小基线SAR干涉(SBAS)技术,对青藏高原沱沱河地区地面形变和冻融过程进行了研究.探测到的地面位移... 相似文献
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A GIS-Based Tool for Spatial and Distributed Hydrological Modelling: CLASS Spatial Analyst 总被引：1，自引：0，他引：1
CLASS Spatial Analyst is a GIS tool which can be used to support spatially distributed hydrological modelling. The tool generates a number of spatial layers that can be used for many practical applications. These include climate zoning, multi‐resolution DEMs, Compound Topographic Index (CTI) (also referred to as Topographic Wetness Index, TWI), lateral multiple flow paths, accumulation and dispersion of water and solutes from hazard areas, estimation of soil depth, soil material/horizon distribution and soil moisture storage capacity in different parts of the landscape. Although each of these tasks can be undertaken separately using spatial software packages such as ArcGIS, GRASS, TIME, and MapInfo, this tool puts together all these tasks into a single application which provides the user with an option of undertaking some or all of them within this application. The technology used in this tool is supported by various peer‐reviewed publications (e.g. Tarboton 1997 , Gallant and Dowling 2003 ). 相似文献
6.
DEM分辨率对小流域地形水文特征提取的影响 总被引：1，自引：0，他引：1
基于ArcGIS水文分析工具研究DEM分辨率对提取流域地形和水文参数的影响,选择黄土丘陵沟壑区典型小流域—韭园沟流域为实验区,该流域地形复杂,沟壑纵横,DEM分辨率变化对其地形表达有很大影响。研究表明,DEM分辨率对小流域面积、流域高程、坡向的表达或提取精度影响较小,而对坡度、河道长度、河网密度和河道分级等因子提取有较大影响。 相似文献
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基于高精度曲面模型的DEM构建与误差分析 总被引：1，自引：1，他引：0
引入地形表达误差(terrain representation error,Etr),选择标准曲面和甘肃省董志塬地区作为研究对象,利用窗口分析法实现Etr的提取;用统计分析法得出Etr随网格分辨率变化的回归方程;根据误差传播定律计算DEM中误差。数值结果表明,该方法能更准确的计算HASM生成的DEM精度;相同的采样数下,HASM较传统方法(IDW,Spline和Kriging)能生成更高精度和分辨率的DEM。在难以获取已知数据的地区,HASM提供了生成相对准确DEM的高效工具。 相似文献
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A Comparison Between Contour Elevation Data Sources for DEM Creation and Soil Carbon Prediction, Coshocton, Ohio 总被引：1，自引：0，他引：1
A raster and vector GIS was created for the North Appalachian Experimental Watershed (NAEW) from legacy (1960) 1:2,400‐scale contour maps. The intent of the study was to use terrain data for the spatial modeling of soil organic carbon. It was hypothesized that DEMs derived from these data would be more accurate and therefore more useful for terrain‐based soil modeling than those from USGS 1:24,000‐scale contour data. Central tasks for this study were to digitally capture the 1:2,400‐scale maps, convert digital contour data sources to raster DEMs at multiple resolutions, and derive terrain attributes. A flexible approach was adopted, using software outside of mainstream GIS sources where scientifically or practically advantageous. Elevation contours and streamlines were converted to raster DEMs using ANUDEM. DEMs ranging in resolution from 0.5–30 m were tested for accuracy against precision carrier‐phase GPS data. The residual standard deviation was 1.68 meters for the USGS DEM and 0.36 meters for the NAEW DEM. The optimal horizontal resolution for the NAEW DEM was 5 m and for the USGS 10 m. Five and 10 m resolution DEMs from both data sources were tested for carbon prediction. Multiple terrain parameters were derived as proxies for surficial processes. Soil samples (n = 184) were collected on four zero‐order watersheds (conventional tillage, no‐till, hay and pasture). Multiple least squares regressions (m.l.s.) were used to predict mass C (kg m?2, 30 cm depth) from topographic information. Model residuals were not spatially autocorrelated. Statistically significant topographic parameters were attained most consistently from the 5 m NAEW DEM. However, topography was not a strong predictor of carbon for these watersheds, with r2 ranging from 0.23 to 0.58. 相似文献
10.
K. H. V. Durga Rao V. Bhanumurthy P. S. Roy 《Journal of the Indian Society of Remote Sensing》2009,37(4):587-600
Hydrological modelling of large river catchments is a challenging task for water resources engineers due to its complexity
in collecting and handling of both spatial and non-spatial data such as rainfall, gauge discharges, and topographic parameters.
In this paper an attempt has been made to use satellite-based rainfall products such as Climatic Prediction Centre (CPC)-National
Oceanic and Atmospheric Administration (NOAA) data for hydrological modelling of larger catchment where the limited field
rainfall data is available. Digital Elevation Models (DEM) such as Global DEM (1 km resolution) and Shuttle Radar Topography
Mission (SRTM) 3-arc second (90 m resolution) DEM have been used to extract topographic parameters of the basin for hydrological
modelling of the study area. Various popular distributed models have been used in this study for computing excess rainfall,
direct runoff from each sub-basin, and flow routing to the main outlet. The Brahmaputra basin, which is very complex both
hydraulically and hydrologically due to its shape, size, and geographical location, has been examined as study area in this
study. A landuse map derived from the satellite remote sensing data in conjunction with DEM and soil textural maps have been
used to derive various basin and channel characteristics such as each sub-basin and channel slope, roughness coefficients,
lag-time. Percentage of residual flows computed between observed flows and simulated flows using Global and SRTM DEMs are
discussed. It is found that the topographic parameters computed using SRTM DEM could improve the model accuracy in computing
flood hydrograph. Need of using better resolution satellite data products and the use of high-density field discharge observations
is discussed. 相似文献
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Previous evaluations of viewshed analyses have raised concerns about the accuracy and repeatability of the process. Digital elevation model (DEM) errors, the limited spatial resolution of DEMs, and differing algorithms employed by different GIS packages have all been suggested as possible sources for inaccuracy and non‐repeatability. This study compared a field surveyed viewshed to predicted viewsheds generated using a variety of software packages and DEM databases, some of which contained known amounts of error. We found that each of the factors suggested by previous authors contributes to errors in predicted viewsheds. DEM errors contribute most to the discrepancies between surveyed and predicted viewsheds, and the majority of their negative impact occurred at very low levels of DEM error. Differing algorithms used by different GIS packages also contribute significantly to surveyed/predicted viewshed discrepancies, but more importantly, result in predicted viewsheds that disagree with one other, thereby confounding comparisons of results generated with differing software systems. Finally, the spatial resolution of DEMs also has a significant effect on the degree of agreement between surveyed and predicted viewsheds, but the magnitude of this effect is not as great as are the effects produced by DEM errors. 相似文献
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《地理信息系统科学与遥感》2013,50(3):306-329
Research on the issue of climate change and its influence on ice sheets calls for increasing use of methods based on remote measurements and monitoring. Work on the Devon Island Ice Cap in Canada demonstrated the value of interferometric synthetic aperture radar. Analyses of two image pairs yielded a digital elevation model that could be used for evaluations of ice mass dimensions and characteristics. This method was found to produce metric accuracy with a resolution of 100 m geocoded DEM and with an accuracy of 5.43 m compared to field-derived GPS measurements. 相似文献
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An enhanced approach for surface flow routing over drainage‐constrained triangulated irregular networks 
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下载免费PDF全文 The accuracy and efficiency of the simulations in distributed hydrological models must depend on the proper estimation of flow directions and paths. Numerous studies have been carried out to delineate the drainage patterns based on gridded digital elevation models (DEMs). The triangulated irregular network (TIN) has been increasingly applied in hydrological applications due to the advantages of high storage efficiency and multi‐scale adaptive performance. Much of the previous literature focuses mainly on filling the depressions on gridded DEMs rather than treating the special cases in TIN structures, which has hampered its applications to hydrological models. This study proposes a triangulation‐based solution for the removal of flat areas and pits to enhance the simulation of flow routing on triangulated facet networks. Based on the drainage‐constrained TIN generated from only a gridded DEM by the compound point extraction (CPE) method, the inconsistent situations including flat triangles, V‐shape flat edges and sink nodes are respectively identified and rectified. The optimization algorithm is an iterative process of TIN reconstruction, in which the flat areas are generalized into their center points and the pits are rectified by embedding break lines. To verify the proposed algorithm and investigate the potential for flow routing, flow paths of steepest descent are derived by the vector‐based tracking algorithm based on the optimized TIN. A case study of TIN optimization and flow path tracking was performed on a real‐world DEM. The outcomes indicate that the proposed approach can effectively solve the problem of inconsistencies without a significant loss in accuracy of the terrain model. 相似文献
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J. Neumeyer F. Barthelmes O. Dierks F. Flechtner M. Harnisch G. Harnisch J. Hinderer Y. Imanishi C. Kroner B. Meurers S. Petrovic Ch. Reigber R. Schmidt P. Schwintzer H. -P. Sun H. Virtanen 《Journal of Geodesy》2006,79(10-11):573-585
Gravity recovery and climate experiment (GRACE)-derived temporal gravity variations can be resolved within the μgal (10?8 m/s 2) range, if we restrict the spatial resolution to a half-wavelength of about 1,500 km and the temporal resolution to 1 month. For independent validations, a comparison with ground gravity measurements is of fundamental interest. For this purpose, data from selected superconducting gravimeter (SG) stations forming the Global Geodynamics Project (GGP) network are used. For comparison, GRACE and SG data sets are reduced for the same known gravity effects due to Earth and ocean tides, pole tide and atmosphere. In contrast to GRACE, the SG also measures gravity changes due to load-induced height variations, whereas the satellite-derived models do not contain this effect. For a solid spherical harmonic decomposition of the gravity field, this load effect can be modelled using degree-dependent load Love numbers, and this effect is added to the satellite-derived models. After reduction of the known gravity effects from both data sets, the remaining part can mainly be assumed to represent mass changes in terrestrial water storage. Therefore, gravity variations derived from global hydrological models are applied to verify the SG and GRACE results. Conversely, the hydrology models can be checked by gravity variations determined from GRACE and SG observations. Such a comparison shows quite a good agreement between gravity variation derived from SG, GRACE and hydrology models, which lie within their estimated error limits for most of the studied SG locations. It is shown that the SG gravity variations (point measurements) are representative for a large area within the accuracy, if local gravity effects are removed. The individual discrepancies between SG, GRACE and hydrology models may give hints for further investigations of each data series. 相似文献
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随着全球气候变化和人类活动剧增,青藏高原的多年冻土环境逐渐变得越来越脆弱。作为青藏高原最重要的基础设施之一,青藏输电线路已于2011年建成并投入使用。由于恶劣的气候和冻土的冻融作用,青藏输电线路部分区域的稳定性遭到破坏,为了保障输电线路的安全运营,需要对输电杆塔稳定性进行监测。传统监测方法（GPS和水准测量）对输电杆塔形变监测存在局限性。本文使用TerraSAR-X ST模式高分辨率SAR数据,采用考虑温度热膨胀形变模型的时序InSAR方法对青藏高原北麓河地区的输电线路杆塔进行形变监测,获得了输电杆塔和通信铁塔的形变速度、高度和热膨胀。结果证实了高分辨率时序InSAR技术在输变电工程形变监测应用中具有广阔的应用前景。 相似文献
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数字高程模型地形描述精度量化模拟研究 总被引：65，自引：3，他引：65
在首先提出数字高程模型（DEM）地形描述误差（Et)概念的基础上，以我国5个不同地貌类型区为试验样区，采用比较分析的方法，研究EDEM地形描述误差的成因、影响因素、量测方法以及误差的数学模拟途径。统计分析的结果证明DEM地形描述误差与DEM空间分辨率及其地面粗糙度之间存在着线性相关关系，回归分析结果显示，DEM地形描述误差Et的均方差RMS值可以表达为DEM水平分辨率（R）与地面垂直曲率（V）的函数：RMS Et=(0.0063V 0.0066)R-0.022V 0.2415。该结果可用以估算估算所建立的DEM的地形描述精度，也为确定适宜的DEM分辨率提供了理论依据。 相似文献
19.
利用主成分分析揭示变量之间关系的特性,进而提出一种既能保证较高精度又能较好地保持地形形态特征的DEM格网聚合方法。首先根据主成分变换模型推导DEM格网聚合数学公式,构建主成分聚合模型;然后以30m分辨率DEM转换为90m分辨率DEM为例,根据格网点属性间的权重关系聚合重构DEM。在此基础上,以均值聚合和双线性重采样聚合方法为比较对象,从聚合前后的检查点高程偏差的统计描述、空间分布与自相关性、地形形态保持程度方面分析3种聚合策略下重构DEM的误差特性。最后运用描述统计、半变异分析和等高线套合方法,定量评价主成分聚合重构DEM的质量效果。试验分析结果表明,同均值聚合和重采样聚合相比较,该方法重构的DEM既能保持较高精度,又能很好地保持地形形态特征。 相似文献
20.
The Amazon landscape spatial variability and anisotropic trends in the Uatumã and Urubu River regions are evaluated using geomorphometric techniques such as fractal dimension, drainage network density and semivariogram. These procedures were applied to the digital elevation model (DEM) of the Shuttle Radar Topography Mission (SRTM). This evaluation facilitated the definition of geomorphometric domains with different degrees of roughness (fractal dimension) and elevation (semivariogram). These areas are consistent with known qualitative relief types. Furthermore, known geological structures in the subsurface and surface apparently influence the spatial variability of these geomorphometric variables. This is the Silves area case, where the hilly topography exhibits several annular and radial rivers, denoting subsurface control due to faults and folds that were mapped by seismic surveys. Another possible influence example is the spatial coincidence between structures mapped by magnetic data with low dissection zones delineated as a result of drainage network density analysis. In addition to the spatial distribution, the anisotropic trends of these geomorphometric variables were analyzed and compared with geological and geophysical information. Results indicate that the predominant directions for topographic semivariance anisotropy are NNE–SSW and NE–SW for the interfluvial regions, as well as NW–SE for the alluvial plains. The highest agglomeration direction in the drainage network, as shown by its anisotropy, coincides with the studied region’s current maximum horizontal stress direction, except in the floodplains. The direction with the most pronounced roughness, NNE–SSW, coincides with the direction of waterfalls and rapids. This study demonstrates that spatial variability knowledge and anisotropic trends of geomorphometric parameters is useful to understand the geology and geomorphology of the Central Amazon region. 相似文献