Evaluation of ASTER GDEM and SRTM and their suitability in hydraulic modelling of a glacial lake outburst flood in southeast Tibet     

Weicai Wang  Xiaoxin Yang  Tandong Yao 《水文研究》2012,26(2):213-225

The resolution and accuracy of digital elevation models (DEMs) can affect the hydraulic simulation results for predicting the effects of glacial lake outburst floods (GLOFs). However, for the Tibetan Plateau, high‐quality DEM data are often not available, leaving researchers with near‐global, freely available DEMs, such as the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM) and the Shuttle Radar Topography Mission data (SRTM) for hydraulic modelling. This study explores the suitability of these two freely available DEMs for hydraulic modelling of GLOFs. Our study focused on the flood plain of a potentially dangerous glacial lake in southeastern Tibet, to evaluate the elevation accuracy of ASTER GDEM and SRTM, and their suitability for hydraulic modelling of GLOFs. The elevation accuracies of ASTER GDEM and SRTM were first validated against field global position system (GPS) survey points, and then evaluated with reference to the relatively high precision of 1:50 000 scale DEM (DEM5) constructed from aerial photography. Moreover, the DEM5, ASTER GDEM and SRTM were used as basic topographic data to simulate peak discharge propagation, as well as flood inundation extent and depth in the Hydrologic Engineering Center's River Analysis System one‐dimensional hydraulic model. Results of the three DEM predictions were compared to evaluate the suitability of ASTER GDEM and SRTM for GLOF hydraulic modelling. Comparisons of ASTER GDEM and SRTM each with DEM5 in the flood plain area show root‐mean‐square errors between the former two as ± 15·4 m and between the latter two as ± 13·5 m. Although SRTM overestimates and ASTER GDEM underestimates valley floor elevations, both DEMs can be used to extract the elevations of required geometric data, i.e. stream centre lines, bank lines and cross sections, for flood modelling. However, small errors still exist in the cross sections that may influence the propagation of peak discharge. The flood inundation extent and mean water depths derived from ASTER GDEM predictions are only 2·2% larger and 2·3‐m deeper than that of the DEM5 predictions, whereas the SRTM yields a flood zone extent 6·8% larger than the DEM5 prediction and a mean water depth 2·4‐m shallower than the DEM5 prediction. The modelling shows that, in the absence of high‐precision DEM data, ASTER GDEM or SRTM DEM can be relied on for simulating extreme GLOFs in southeast Tibet. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Satellite Data for a Rapid Assessment of Tsunami Inundation Areas after the 2011 Tohoku Tsunami     

María Teresa Ramírez-Herrera  José Antonio Navarrete-Pacheco 《Pure and Applied Geophysics》2013,170(6-8):1067-1080

The M _w = 9.0 earthquake that occurred off the coast of Japan’s Tohoku region produced a great tsunami causing catastrophic damage and loss of life. Within hours of the tsunami event, satellite data were readily available and massive media coverage immediately circulated thousands of photographs and videos of the tsunami. Satellite data allow a rapid assessment of inundated areas where access can be difficult either as a result of damaged infrastructure (e.g., roads, bridges, ports, airports) or because of safety issues (e.g., the hazard at Nuclear Power Plant at Fukushima). In this study, we assessed in a day tsunami inundation distances and runup heights using satellite data (very high-resolution satellite images from the GeoEye1 satellite and from the DigitalGlobe worldview, SRTM and ASTER GDEM) of the Tohoku region, Northeast Japan. Field survey data by Japanese and other international scientists validated our results. This study focused on three different locations. Site selection was based on coastal morphologies and the distance to the tsunami source (epicenter). Study sites are Rikuzentakata, Oyagawahama, and Yagawahama in the Oshika Peninsula, and the Sendai coastal plain (Sendai City to Yamamoto City). Maximum inundation distance (6 km along the river) and maximum runup (39 m) at Rikuzentakata estimated from satellite data agree closely with the 39.7 m inundation reported in the field. Here the ria coastal morphology and horn shaped bay enhanced the tsunami runup and effects. The Sendai coastal plain shows large inundation distances (6 km) and lower runup heights. Natori City and Wakabayashi Ward, on the Sendai plain, have similar runup values (12 and 16 m, respectively) obtained from SRTM data; these are comparable to those obtained from field surveys (12 and 9.5 m). However, at Yagawahama and Oyagawahama, Miyagi Prefecture, both SRTM and ASTER data provided maximum runup heights (41 to 45 m and 33 to 34 m, respectively), which are higher than those measured in the field (about 27 m). This difference in DEM and field data is associated with ASTER and SRTM DEM’s pixel size and vertical accuracy, the latter being dependent on ground coverage, slope, aspect and elevation. Countries with less access to technology and infrastructure can benefit from the use of satellite imagery and freely available DEMs for an initial, pre-field surveys, rapid estimate of inundated areas, distances and runup, and for assisting in hazard management and mitigation after a natural disaster.  相似文献   

Evaluating DEM source and resolution uncertainties in the Soil and Water Assessment Tool     

Shengpan Lin  Changwei Jing  Neil A. Coles  Vincent Chaplot  Nathan J. Moore  Jiaping Wu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(1):209-221

DEMs as important input parameters of environmental risk assessment models are notable sources of uncertainties. To illustrate the effect of DEM grid size and source on model outputs, a widely used watershed management model, the Soil and Water Assessment Tool (SWAT), was applied with two newly available DEMs as inputs (i.e. ASTER GDEM Version 1, and SRTM Version 4.1). A DEM derived from 1:10,000 high resolution digital line graph (DLG) was used as a baseline for comparisons. Eleven resample resolutions, from 5 to 140?m, were considered to evaluate the impact of DEM resolution on SWAT outputs. Results from a case study in South-eastern China indicate that the SWAT predictions of total phosphorus and total nitrogen decreased substantially with coarser resample resolution. A slightly decreasing trend was found in the SWAT predicted sediment when DEMs were resampled to coarser resolutions. The SWAT predicted runoff was not sensitive to resample resolution. For different data sources, ASTER GDEM did not perform better than SRTM in SWAT simulations even it was provided with a smaller grid size and higher vertical accuracy. The predicted outputs based on ASTER GDEM and SRTM were similar, and much lower than the ones based on DLG. This study presents potential uncertainties introduced by DEM resolutions and data sources, and recommends strategies choosing DEMs based on research objects and maximum acceptable errors.  相似文献   

Evaluation of DEM generation based on Interferometric SAR using TanDEM-X data in Tokyo     

《Physics and Chemistry of the Earth》2015

This study is focused on the evaluation of a Digital Elevation Model (DEM) for Tokyo, Japan from data collected by the recently launched TerraSAR add-on for Digital Elevation Measurements (TanDEM-X), satellite of the German Aerospace Center (DLR). The aim of the TanDEM-X mission is to use Interferometric SAR techniques to generate a consistent high resolution global DEM dataset. In order to generate an accurate global DEM using TanDEM-X data, it is important to evaluate the accuracy at different sites around the world. Here, we report our efforts to generate a high-resolution DEM of the Tokyo metropolitan region using TanDEM-X data. We also compare the TanDEM-X DEM with other existing DEMs for the Tokyo region. Statistical techniques were used to calculate the elevation differences between the TanDEM-X DEM and the reference data. Two high-resolution LiDAR DEMs are used as independent reference data. The vertical accuracy of the TanDEM-X DEM evaluated using the Root Mean Square Error (RMSE) is considerably higher than the existing global digital elevation models. However, the local area DEM generated by Geospatial Information Authority of Japan (GSI DEM) showed the highest accuracy among all non-LiDAR DEM’s. The vertical accuracy in terms of RMSE estimated using the 2 m LiDAR as reference is 3.20 m for TanDEM-X, 2.44 m for the GSI, 7.00 m for SRTM DEM and 10.24 m for ASTER-GDEM. We also compared the accuracy of TanDEM-X with the other DEMs for different types of land cover classes. The results show that the absolute elevation error of TanDEM-X is higher for urban and vegetated areas, likewise to those observed for other global DEM’s. This is probably because the radar signals used by TanDEM-X tend to measure the first reflective surface that is encountered, which is often the top of the buildings or canopy. Hence, the TanDEM-X based DEM is more akin to a Digital Surface Model (DSM).  相似文献   

Evaluation of on-line DEMs for flood inundation modeling   总被引：1，自引：0，他引：1  

Brett F. Sanders 《Advances in water resources》2007

Recent and highly accurate topographic data should be used for flood inundation modeling, but this is not always feasible given time and budget constraints so the utility of several on-line digital elevation models (DEMs) is examined with a set of steady and unsteady test problems. DEMs are used to parameterize a 2D hydrodynamic flood simulation algorithm and predictions are compared with published flood maps and observed flood conditions. DEMs based on airborne light detection and ranging (LiDAR) are preferred because of horizontal resolution, vertical accuracy (∼0.1 m) and the ability to separate bare-earth from built structures and vegetation. DEMs based on airborne interferometric synthetic aperture radar (IfSAR) have good horizontal resolution but gridded elevations reflect built structures and vegetation and therefore further processing may be required to permit flood modeling. IfSAR and shuttle radar topography mission (SRTM) DEMs suffer from radar speckle, or noise, so flood plains may appear with non-physical relief and predicted flood zones may include non-physical pools. DEMs based on national elevation data (NED) are remarkably smooth in comparison to IfSAR and SRTM but using NED, flood predictions overestimate flood extent in comparison to all other DEMs including LiDAR, the most accurate. This study highlights utility in SRTM as a global source of terrain data for flood modeling.  相似文献   

Slope angle and aspect as influencing factors on the accuracy of the SRTM and the ASTER GDEM databases     

《Physics and Chemistry of the Earth》2015

Presently, the application of digital elevation or surface models have increasing relevance in all areas of scientific research and in practical engineering applications. The ASTER GDEM and SRTM databases are the most widely used digital surface models, due to their free accessibility and global coverage. The SRTM model was produced using a radar-based technique and the ASTER GDEM was developed using optical stereo image-pairs. Therefore, as all models contain errors (i.e. differences stemming from real surface or vertical biases), errors in these models will also differ. Our aim was to examine these vertical biases and to calculate the rate of error variance. A TIN (Triangulated Irregular Network) model was used as a reference surface, derived from the contour lines of a large scale topographic map. Errors were evaluated with statistical and geoinformation techniques. We discovered significant differences between the surfaces. The mean difference between topographic elevations minus the SRTM-V2 is +2.6 ± 4 m, while the mean difference between topographic elevations minus the SRTM-V3 is +2.7 ± 2.5 m. With the GDEM, the mean difference was 2.7 ± 9.1 m. Furthermore, we found that in the case of SRTM, the differences were significant considering the aspects and the steepness of the slopes: southern and eastern directions and larger slope angles showed greater differences compared to the reference data. The GDEM V2 DEM had a larger error variance, but the error did not vary significantly with slope angle.  相似文献   

Towards a More Realistic Depiction of the Earth’s Surface on Maps     

Jacek Drachal  Anna Dębowska 《Pure and Applied Geophysics》2014,171(6):1061-1075

In 2000, the shuttle radar topography mission (SRTM) produced the most complete, highest resolution digital elevation model (DEM) of the Earth. These data were used to create global 3″ DEM and to correct 30″ DEM which are both available on the internet. After a careful survey in the Institute of Geodesy and Cartography, Poland, these elevation data were recognized as extremely valuable and worth developing a unique form of visualization. As a result, a new design of a physical map of Europe at scale of 1:10 million was developed. For depicting the shape of the terrain, an original modification of combined shaded relief was employed, to reveal all the nuances of elevation data. True colors of the Earth’s surface represented on the map originated from MODIS satellite image. The combination of true colors and terrain features made a realistic map, showing the landscapes as if from a point above the Earth. The image of the terrain is extremely detailed as it is based on the abundance of data defining the elevation of each point of land.  相似文献   

Evaluation of remotely‐sensed DEMs and modification based on plausibility rules and initial sediment budgets of an artificially‐created catchment     

Anna Schneider  Horst H. Gerke  Thomas Maurer  Stefan Seifert  Rossen Nenov  Reinhard F. Hüttl 《地球表面变化过程与地形》2012,37(7):708-725

To quantify landscape change resulting from processes of erosion and deposition and to establish spatially distributed sediment budgets, ‘models of change’ can be established from a time series of digital elevation models (DEMs). However, resolution effects and measurement errors in DEMs may propagate to these models. This study aimed to evaluate and to modify remotely‐sensed DEMs for an improved quantification of initial sediment mass changes in an artificially‐created catchment. DEMs were constructed from photogrammetry‐based, airborne (ALS) and ground‐based laser scanning (TLS) data. Regions of differing morphological characteristics and vegetation cover were delineated. Three‐dimensional (3D) models of volume change were established and mass change was derived from these models. DEMs were modified region‐by‐region for rill, interrill and alluvial areas, based on logical and hydro‐geomorphological principles. Additional DEMs were constructed by combining multi‐source, modified data. Models were evaluated by comparison with d‐GPS reference data and by considering sediment budget plausibility. Comprehensive evaluation showed that DEM usability depends on a relation between the technique used to obtain elevation data, surface morphology and vegetation cover characteristics. Photogrammetry‐based DEMs were suited to quantification of change in interrill areas but strongly underestimated surface lowering in erosion rills. TLS DEMs were best suited to rill areas, while ALS DEMs performed best in vegetation‐covered alluvial areas. Agreement with reference data and budget plausibility were improved by modifications to photogrammetry‐ and TLS‐based DEMs. Results suggest that artefacts in DEMs can be reduced and hydro‐geomorphic surface structures can be better represented by applying region‐specific modifications. Photogrammetry‐based DEMs can be improved by combining higher and lower resolution data in defined structural units and applying modifications based on principles given by characteristic hydro‐geomorphic evolution. Results of the critical comparative evaluation of remotely‐sensed elevation data can help to better interpret DEM‐based quantifications of earth‐surface processes. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Topographic analyses of K*lauea Volcano, Hawai'i, from interferometric airborne radar     

Scott K. Rowland  Mary E. MacKay  Harold Garbeil  Peter J. Mouginis-Mark 《Bulletin of Volcanology》1999,61(1-2):1-14

 We analyze digital topographic data collected in September 1993 over a ∼500-km² portion of K*lauea Volcano, Hawai'i, by the C-band (5.6-cm wavelength) topographic synthetic aperture radar (TOPSAR) airborne interferometric radar. Field surveys covering an ∼1-km² area of the summit caldera and the distal end of an ∼8-m-thick 'a'* flow indicate that the 10-m spatial resolution TOPSAR data have a vertical accuracy of 1–2 m over a variety of volcanic surfaces. After conversion to a common datum, TOPSAR data agree favorably with a digital elevation model (DEM) produced by the U.S. Geological Survey (USGS), with the important exception of the region of the ongoing eruption (which postdates the USGS DEM). This DEM comparison gives us confidence that subtracting the USGS data from TOPSAR data will produce a reasonable estimate of the erupted volume as of September 1993. This subtraction produces dense rock equivalent (DRE) volumes of 392, 439, and 90×10⁶ m³ for the Pu'u '*'*, K*pa'ianah*, and episode 50–53 stages of the eruption, respectively. These are 124, 89, and 94% of the volumes calculated by staff of the Hawaiian Volcano Observatory (HVO) but do not include lava of K*pa'ianah* and episodes 50–53 that flowed into the ocean and are thus invisible to TOPSAR. Accounting for this lava increases the TOPSAR volumes to 124, 159, and 129% of the HVO volumes. Including the ±2-m uncertainty derived from the field surveys produces TOPSAR-derived volumes for the eruption as a whole that range between 81 and 125% of the USGS-derived values. The vesicularity- and ocean-corrected TOPSAR volumes yield volumetric eruption rates of 4.5, 4.5, and 2.7 m³/s for the three stages of the eruption, which compare with HVO-derived values of 3.6, 2.8, and 2.1 m³/s, respectively. Our analysis shows that care must be taken when vertically registering the TOPSAR and USGS DEMs to a common datum because C-band TOPSAR penetrates only partially into thick forest and therefore produces a DEM within the tree canopy, whereas the USGS DEM is adjusted for vegetation. Received: 28 April 1998 / Accepted: 1 February 1999  相似文献   

基于CryoSat-2测高数据的全南极冰盖DEM的建立与精度评估   总被引：1，自引：0，他引：1       下载免费PDF全文

李斐  肖峰  张胜凯  鄂栋臣  程晓  郝卫峰  袁乐先  左耀文 《地球物理学报》2017,60(5):1617-1629

数字高程模型(DEM)是南极冰盖变化研究的基础,由于现场实测数据的稀缺,卫星测高数据是南极地区构建DEM的'主要数据来源.CryoSat-2是新一代用于极地冰盖、海冰监测的测高卫星,本文利用2012-12-2015-01两个完整周期的CryoSat-2测高数据建立一个新的南极冰盖DEM.坡度是影响卫星测高精度的重要因素之一,利用改进的重定位方法对CryoSat-2数据进行坡度改正.插值方法是影响DEM精度的重要因素,通过对几种常用插值方法的比较,最后选用克里金插值方法对测高数据进行插值,建立了1km分辨率的南极DEM.在88°S以南的CryoSat-2数据空白区,利用南极数字数据库(ADD)的等高线数据对DEM进行填补,建立了全南极冰盖DEM.利用ICESat卫星测高数据、IceBridge航空测高数据以及GPS地面实测数据对新建立的CryoSat-2 DEM进行精度验证,并与Bamber 1 km DEM、ICESat DEM、RAMPv2 DEM以及JLB97 DEM等四种国际上常用的南极DEM进行比较.结果表明:新建立的CryoSat-2 DEM的整体精度约为0.730±8.398 m;在冰弯顶部区域,DEM精度优于1 m;在冰架上,DEM精度约为4 m;在内陆冰盖大部分地区,DEM精度优于10 m;在地形复杂的山区和沿海边缘地区,DEM误差超过150 m.  相似文献   

利用CryoSat-2波形数据建立南极Lambert冰川流域DEM          下载免费PDF全文

肖峰  李斐  张胜凯  郝卫峰  耿通  宣越 《地球物理学报》2020,63(8):2893-2900

Lambert冰川-Amery冰架系统是南极冰盖最大的冰流系统之一,对南极冰盖物质平衡研究有着重要的作用.数字高程模型(DEM)是进行南极冰盖研究的基础.本文基于CryoSat-2 L1b波形数据,研究建立了Lambert冰川流域高分辨率DEM.测高卫星返回波形在冰盖区域存在变形,需进行波形重跟踪处理.利用交叉点分析方法对重心偏移法(OCOG)、阈值法和β参数法等常用的波形重跟踪方法对不同类型的CryoSat-2波形的适用性进行了研究.最后,利用克里金插值方法建立了500 m分辨率的Lambert冰川流域DEM——LAS DEM (Lambert Glacier-Amery Ice Shelf system DEM).利用ICESat卫星测高数据和GPS地面实测数据对LAS DEM进行精度验证,并与另外两种基于CryoSat-2数据的南极DEM进行了对比.结果表明:LAS DEM的整体精度约为0.295±2.7 m,优于另外两种CryoSat-2 DEM;在冰盖内陆地区,LAS DEM的高程误差在2 m之内;在Amery冰架上,LAS DEM的精度优于1 m.  相似文献   

Application of globally available,coarse-resolution digital elevation models for delineating valley bottom segments of varying length across a catchment     

Sana Khan  Kirstie A. Fryirs 《地球表面变化过程与地形》2020,45(12):2788-2803

The worldwide availability of digital elevation models (DEMs) has enabled rapid (semi-)automated mapping of earth surface landforms. In this paper, we first present an approach for delineating valley bottom extent across a large catchment using only publicly available, coarse-resolution DEM input. We assess the sensitivity of our results to variable DEM resolution and find that coarse-resolution datasets (90 m resolution) provide superior results. We also find that LiDAR-derived DEMs produce more realistic results than satellite-derived DEMs across the full range of topographic settings tested. Satellite-derived DEMs perform more effectively in moderate topographic settings, but fail to capture the subtleties of valley bottom extent in mild gradient, low-lying topography and in narrow headwater reaches. Second, we present a semi-automated technique within ArcGIS for delineating valley bottom segments using DEM-derived network scale metrics of valley bottom width and slope. We use an unsupervised machine-learning technique based on the k-means clustering algorithm to solve a conundrum in GIS-based geomorphic analysis of rivers: the delineation of valley bottom segments of variable length. The delineation of valley bottom segments provides a coarse-scale entry point into automated geomorphic analysis and characterization of river systems. © 2020 John Wiley & Sons, Ltd.  相似文献   

Improvement of streams hydro‐geomorphological assessment using LiDAR DEMs     

Pascale M. Biron  Guénolé Choné  Thomas Buffin‐Bélanger  Sylvio Demers  Taylor Olsen 《地球表面变化过程与地形》2013,38(15):1808-1821

Hydro‐geomorphological assessments are an essential component for riverine management plans. They usually require costly and time‐consuming field surveys to characterize the spatial variability of key variables such as flow depth, width, discharge, water surface slope, grain size and unit stream power throughout the river corridor. The objective of this research is to develop automated tools for hydro‐geomorphological assessments using high‐resolution LiDAR digital elevation models (DEMs). More specifically, this paper aims at developing geographic information system (GIS) tools to extract channel slope, width and discharge from 1 m‐resolution LiDAR DEMs to estimate the spatial distribution of unit stream power in two contrasted watersheds in Quebec: a small agricultural stream (Des Fèves River) and a large gravel‐bed river (Matane River). For slope, the centreline extracted from the raw LiDAR DEM was resampled at a coarser resolution using the minimum elevation value. The channel width extraction algorithm progressively increased the centerline from the raw DEM until thresholds of elevation differences and slopes were reached. Based on the comparison with over 4000 differential global positioning system (GPS) measurements of the water surface collected in a 50 km reach of the Matane River, the longitudinal profile and slope estimates extracted from the raw and resampled LiDAR DEMs were in very good agreement with the field measurements (correlation coefficients ranging from 0 · 83 to 0 · 87) and can thus be used to compute stream power. The extracted width also corresponded very well to the channel as seen from ortho‐photos, although the presence of bars in the Matane River increased the level of error in width estimates. The estimated maximum unit stream power spatial patterns corresponded well with field evidence of bank erosion, indicating that LiDAR DEMs can be used with confidence for initial hydro‐geomorphological assessments. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Impact of grid resolution on the integrated and distributed response of a coupled surface–subsurface hydrological model for the des Anglais catchment,Quebec     

Mauro Sulis  Claudio Paniconi  Matteo Camporese 《水文研究》2011,25(12):1853-1865

Digital elevation models (DEMs) at different resolutions (180, 360, and 720 m) are used to examine the impact of different levels of landscape representation on the hydrological response of a 690‐km² catchment in southern Quebec. Frequency distributions of local slope, plan curvature, and drainage area are calculated for each grid size resolution. This landscape analysis reveals that DEM grid size significantly affects computed topographic attributes, which in turn explains some of the differences in the hydrological simulations. The simulations that are then carried out, using a coupled, process‐based model of surface and subsurface flow, examine the effects of grid size on both the integrated response of the catchment (discharge at the main outlet and at two internal points) and the distributed response (water table depth, surface saturation, and soil water storage). The results indicate that discharge volumes increase as the DEM is coarsened, and that coarser DEMs are also wetter overall in terms of water table depth and soil water storage. The reasons for these trends include an increase in the total drainage area of the catchment for larger DEM cell sizes, due to aggregation effects at the boundary cells of the catchment, and to a decrease in local slope and plan curvature variations, which in turn limits the capacity of the watershed to transmit water downslope and laterally. The results obtained also show that grid resolution effects are less pronounced during dry periods when soil moisture dynamics are mostly controlled by vertical fluxes of evaporation and percolation. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Crew variability in topographic surveys for monitoring wadeable streams: a case study from the Columbia River Basin          下载免费PDF全文

Sara Bangen  Joe Wheaton  Nicolaas Bouwes  Chris Jordan  Carol Volk  Michael B. Ward 《地球表面变化过程与地形》2014,39(15):2070-2086

Digital elevation models (DEMs) derived from ground‐based topographic surveys have become ubiquitous in the field of fluvial geomorphology. Their wide application in spatially explicit analysis includes hydraulic modeling, habitat modeling, and morphological sediment budgeting. However, there is a lack of understanding regarding the repeatability and precision of DEMs derived from ground‐based surveys conducted by different, and inherently subjective, observers. This is of particular concern when we consider the proportion of studies and monitoring programs that are implemented across multiple sites and over time by different observers. We used a case study from the Columbia Habitat Monitoring Program (CHaMP), where seven field crews sampled the same six sites, to quantify the magnitude and effect of observer variability on DEMs interpolated from total station surveys. We quantified the degree to which DEM‐derived metrics and measured geomorphic change were repeatable. Across all six sites, we found an average elevation standard deviation of 0.05 m among surveys, and a mean total range of 0.16 m. A variance partition between site, crew, and unexplained errors for several topographically derived metrics showed that crew variability never accounted for > 1.5% of the total variability. We calculated minor geomorphic changes at one site following a relatively dry flow year between 2012 and 2011. Calculated changes were minimal (unthresholded net changes ±1–3 cm) with six crews detecting an indeterminate sediment budget and one crew detecting a minor net erosional sediment budget. While crew variability does influence the quality of topographic surveys, this study highlights that when consistent surveying methods are employed, the data sets are still sufficient to support derivation of topographic metrics and conduct basic geomorphic change detection. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

An assessment of large-scale flood modelling based on LiDAR data     

Guénolé Choné  Pascale M. Biron  Thomas Buffin-Bélanger  Iulia Mazgareanu  Jeff C. Neal  Christopher C. Sampson 《水文研究》2021,35(8):e14333

Large-scale flood modelling approaches designed for regional to continental scales usually rely on relatively simple assumptions to represent the potentially highly complex river bathymetry at the watershed scale based on digital elevation models (DEMs) with a resolution in the range of 25–30 m. Here, high-resolution (1 m) LiDAR DEMs are employed to present a novel large-scale methodology using a more realistic estimation of bathymetry based on hydrogeomorphological GIS tools to extract water surface slope. The large-scale 1D/2D flood model LISFLOOD-FP is applied to validate the simulated flood levels using detailed water level data in four different watersheds in Quebec (Canada), including continuous profiles over extensive distances measured with the HydroBall technology. A GIS-automated procedure allows to obtain the average width required to run LISFLOOD-FP. The GIS-automated procedure to estimate bathymetry from LiDAR water surface data uses a hydraulic inverse problem based on discharge at the time of acquisition of LiDAR data. A tiling approach, allowing several small independent hydraulic simulations to cover an entire watershed, greatly improves processing time to simulate large watersheds with a 10-m resampled LiDAR DEM. Results show significant improvements to large-scale flood modelling at the watershed scale with standard deviation in the range of 0.30 m and an average fit of around 90%. The main advantage of the proposed approach is to avoid the need to collect expensive bathymetry data to efficiently and accurately simulate flood levels over extensive areas.  相似文献   

Slicer Laser Altimetry In The Eastern Caribbean     

P. Jansma  G. Mattioli  A. Matias 《Surveys in Geophysics》2001,22(5-6):561-579

Data acquired by the airborne Scanning Lidar Imager of Canopies by EchoRecovery (SLICER) laser altimeter provided high-resolution digital topographicdata over Puerto Rico, the Dominican Republic and several of the Lesser AntillesIslands. The instrument was developed by the NASA-Goddard Space Flight Center.It has the capability of multibeam resolution of ground elevations beneath densecanopy areas. Data, therefore, can be used to generate a more accurate representation of the ground surface by removing the vegetation cover. Although internal precision is high (10 cm to 1 m), absolute accuracy is difficult to evaluate and depends on several factors, including the post-processed kinematic GPS (KGPS) flight path for the aircraft platform and clear identification of ground returns in the SLICER waveform. We compared topographic profiles from USGS 30 m and 1:250K DEMs for Puerto Rico with those generated by SLICER and with spot elevations derived from static and continuous GPS surveys. SLICER and KGPS surveys cross at six points in western Puerto Rico. Agreement between both elevation data sets is excellent and well fit (r = 0.921) by a linear model with a final residual bias of -0.501 m for SLICER ground returns relative to KGPS elevations. The agreement between SLICER and USGS 30 m DEMs is also very good with the largest errors associated with steep slopes and high vegetation cover. Residuals between KGPS and USGS 30 m DEMs are +1 ± 25 m, assuming a fixed uniform offset of +43.23 m between WGS84 and mean sea level.  相似文献   

Identification of peneplains by multi‐parameter assessment of digital elevation models          下载免费PDF全文

Vicky L. Haider  Jan Kropáček  István Dunkl  Bianca Wagner  Hilmar von Eynatten 《地球表面变化过程与地形》2015,40(11):1477-1492

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Effects of terrain attributes on snow-cover dynamics in parts of Chenab basin,western Himalayas     

Retinder Kour  Akhouri Pramod Krishna 《水文科学杂志》2013,58(10):1861-1876

ABSTRACT

Terrain variables are the main factors affecting the spatial distribution of snow cover. This paper aims to find a relationship between snow-cover area (SCA) and topographic variables (elevation, slope and aspect), using MODIS Terra data (MOD09A1) in parts of the Chenab basin, western Himalayas. The inter-annual variability of SCA% for each month has been analysed for the years 2000 to 2011. The analysis reveals that mean annual SCA value was maximum (37.89%) in 2005 and minimum (32.07%) in 2001. The slope classes with maximum and minimum SCA% are 5°–10° and 30°–35°, respectively. Among the 16 aspect classes, the ESE-facing slope evinces maximum SCA%. During the snow accumulation period, the expanse at 3600–4300 m elevation, and in the depletion period, 4300–5000 m elevation are found to have maximum rate of change in SCA% per 100 m rise in elevation, i.e. 3.37% and 3.67%, respectively.