Validation studies of global Digital Elevation Models(DEMs)in the existing literature are limited by the diversity and spread of landscapes,terrain types considered and sparseness of groundtruth.Moreover,there are kno...Validation studies of global Digital Elevation Models(DEMs)in the existing literature are limited by the diversity and spread of landscapes,terrain types considered and sparseness of groundtruth.Moreover,there are knowledge gaps on the accuracy variations in rugged and complex landscapes,and previous studies have often not relied on robust internal and external validation measures.Thus,there is still only partial understanding and limited perspective of the reliability and adequacy of global DEMs for several applications.In this study,we utilize a dense spread of LiDAR groundtruth to assess the vertical accuracies of four medium-resolution,readily available,free-access and global coverage 1 arc-second(30 m)DEMs:NASADEM,ASTER GDEM,Copernicus GLO-30,and ALOS World 3D(AW3D).The assessment is carried out at landscapes spread across Cape Town,Southern Africa(urban/industrial,agricultural,mountain,peninsula and grassland/shrubland)and forested national parks in Gabon,Central Africa(low-relief tropical rainforest and high-relief tropical rainforest).The statistical analysis is based on robust accuracy metrics that cater for normal and non-normal elevation error distribution,and error ranking.In Cape Town,Copernicus DEM generally had the least vertical error with an overall Mean Error(ME)of 0.82 m and Root Mean Square Error(RMSE)of 2.34 m while ASTER DEM had the poorest performance.However,ASTER GDEM and NASADEM performed better in the low-relief and high-relief tropical forests of Gabon.Generally,the DEM errors have a moderate to high positive correlation in forests,and a low to moderate positive correlation in mountains and urban areas.Copernicus DEM showed superior vertical accuracy in forests with less than 40%tree cover,while ASTER and NASADEM performed better in denser forests with tree cover greater than 70%.This study is a robust regional assessment of these global DEMs.展开更多
High-quality height reference data are embedded in the accuracy verification processes of most remote sensing terrain applications.The Ice,Cloud,and Land elevation Satellite 2(ICESat-2)/ATL08 terrain product has shown...High-quality height reference data are embedded in the accuracy verification processes of most remote sensing terrain applications.The Ice,Cloud,and Land elevation Satellite 2(ICESat-2)/ATL08 terrain product has shown promising results for estimating ground heights,but it has not been fully evaluated.Hence,this study aims to assess and enhance the accuracy of the ATL08 terrain product as a height reference for the newest versions of the Advanced Spaceborne Thermal Emission and Reflection Radiometer(ASTER),the Shuttle Radar Topography Mission(SRTM),and TanDEM-X(TDX)DEMs over vegetated mountainous areas.We used uncertainty-based filtering method for the ATL08 strong and weak beams to enhance their accuracy.Then,the results were evaluated against a reference airborne LiDAR digital terrain model(DTM),by selecting 10,000 points over the entire area and comparing the accuracy of ASTER,SRTM,and TDX DEMs assessed by the LiDAR DTM to the accuracy of the ASTER,SRTM,and TDX DEMs assessed by the ATL08 strong beams,weak beams,and all beams.We also detected the impact of the terrain aspect,slope,and land cover types on the accuracy of the ATL08 terrain elevations and their relationship with height errors and uncertainty.Our findings show the accuracy of the ATL08 strong beams was enhanced by 43.91%;while the weak beams accuracy was enhanced by 74.05%.Furthermore,slope strongly influenced ATL08 height errors and height uncertainty;especially on the weak beams.The errors induced by the slope significantly decreased when the uncertainty levels were reduced to<20 m.The evaluations of ASTER,SRTM,and TDX DEMs by ATL08 strong and weak beams are close to those assessed by LiDAR DTM points within 0.6 m for the strong beams.These findings indicate that ATL08 strong beams can be used as a height reference over vegetated mountainous regions.展开更多
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 uncertaint...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.展开更多
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 availab...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.展开更多
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 ...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.展开更多
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...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.展开更多
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),whi...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.展开更多
The influence of pre-quaternary underlying terrain on the formation of loess landforms, i.e., the geomorphological inheritance issue, is a focus in studies of loess landforms. On the basis of multi-source information,...The influence of pre-quaternary underlying terrain on the formation of loess landforms, i.e., the geomorphological inheritance issue, is a focus in studies of loess landforms. On the basis of multi-source information, we used GIS spatial analysis methods to construct a simulated digital elevation model of a pre-quaternary paleotopographic surface in a severe soil erosion area of the Loess Plateau. To reveal the spatial relationship between underlying paleotopography and modern terrain, an XY scatter diagram, hypsometric curve, gradient and concavity of terrain profiles are used in the experiments. The experiments show that the altitude, gradient and concavity results have significant linear positive correlation between both terrains, which shows a relatively strong landform inheritance relationship, particularly in the intact and complete loess deposit areas. Despite the current surface appearing somewhat changed from the original shape of the underlying terrain under different erosion forces, we reveal that the modern terrain generally smoothes the topographic relief of underlying terrain in the loess deposition process. Our results deepen understanding of the characteristics of geomorphological inheritance in the formation and evolution of loess landforms.展开更多
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 ana...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-Xizang,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.展开更多
The Longchuan River basin lies within the China Sichuan-Yunnan rhomboid block.The NS-trending Yuanmou-Lvzhi River Fault(YLF),NW-trending Chuxiong-Nanhua Fault(CNF)and Shiyang-Huoshaotun Fault(HSF)are found within the ...The Longchuan River basin lies within the China Sichuan-Yunnan rhomboid block.The NS-trending Yuanmou-Lvzhi River Fault(YLF),NW-trending Chuxiong-Nanhua Fault(CNF)and Shiyang-Huoshaotun Fault(HSF)are found within the basin.The nature of the faults is complex,and the tectonic activity distribution characteristics require further clarification.By extraction from a digital elevation model,the measured longitudinal profile and the geomorphic indices of the Longchuan River,basin showed a stream-length gradient index(SL)of 49–650,hypsometric integral(HI)of 0.27–0.58,drainage basin asymmetry factor(AF)of 3.29–27.47,basin shape index(BS)of 0.87–2.75,valley floor width-to-height ratio(VF)of 0.06–5.40,and evaluation of relative tectonic activity(Iat)of 1.6–2.6.Results showed that river morphology and geomorphological indices in the Longchuan River basin were influenced by tectonic activity,bedrock lithology,climatic conditions,and development time,with tectonic activity playing a dominant role.The relative tectonic activity of the Longchuan River basin was zoned,with a gradual increase in relative tectonic activity from the south to the north.That the slip fault zone primarily controls the tectonic deformation of the Longchuan River basin in central Yunnan and the dynamics of the central Yunnan massif are consistent with the“rigid block lateral extrusion”1model.展开更多
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 la...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.展开更多
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...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.展开更多
0 INTRODUCTION.The global availability of digital elevation model(DEM)data,such as 90-m Shuttle Radar Topography Mission(SRTM)DEM and 30-m Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital ...0 INTRODUCTION.The global availability of digital elevation model(DEM)data,such as 90-m Shuttle Radar Topography Mission(SRTM)DEM and 30-m Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM),has been extensively utilized in morphotectonic analyses(e.g.,Wang et al.,2024;Cheng et al.,2018;Pérez-Pe?a et al.,2010;El Hamdouni et al.,2008).展开更多
Geomorphometric modeling and mapping of Antarctic oases are promising for obtaining new quantitative knowledge about the topography of these unique landscapes and for the further use of morphometric information in Ant...Geomorphometric modeling and mapping of Antarctic oases are promising for obtaining new quantitative knowledge about the topography of these unique landscapes and for the further use of morphometric information in Antarctic research.Within the framework of a project to create a thematic physical-geographical scientific reference geomorphometric atlas of ice-free areas of Antarctica,we performed geomorphometric modeling and mapping of the Bunger Hills(Knox Coast,Wilkes Land,East Antarctica),one of the largest Antarctic oases.By processing a fragment of the Reference Elevation Model of Antarctica(REMA)covering the Bunger Hills and adjacent glaciers,we created,for the first time,a series of 37 medium-to large-scale maps of nine of the most scientifically important morphometric variables(i.e.,slope gradient,slope aspect,vertical curvature,horizontal curvature,maximal curvature,minimal curvature,catchment area,topographic wetness index,and stream power index).The morphometric maps describe the topography of the Bunger Hills in a quantitative,rigorous,and reproducible manner.New morphometric data can be useful for further geological,geomorphological,glaciological,ecological,and hydrological studies of this Antarctic oasis.展开更多
Texture analysis methods offer substantial advantages and potential in examining macro-topographic features of dunes.Despite these advantages,comprehensive approaches that integrate digital elevation model(DEM)with qu...Texture analysis methods offer substantial advantages and potential in examining macro-topographic features of dunes.Despite these advantages,comprehensive approaches that integrate digital elevation model(DEM)with quantitative texture features have not been fully developed.This study introduced an automatic classification framework for dunes that combines texture and topographic features and validated it through a typical coastal aeolian landform,namely,dunes in the Namib Desert.A three-stage approach was outlined:(1)segmentation of dune units was conducted using digital terrain analysis;(2)six texture features(angular second moment,contrast,correlation,variance,entropy,and inverse difference moment)were extracted from the gray-level co-occurrence matrix(GLCM)and subsequently quantified;and(3)texture–topographic indices were integrated into the random forest(RF)model for classification.The results show that the RF model fused with texture features can accurately identify dune morphological characteristics;through accuracy evaluation and remote sensing image verification,the overall accuracy reaches 78.0%(kappa coefficient=0.72),outperforming traditional spectral-based methods.In addition,spatial analysis reveals that coastal dunes exhibit complex texture patterns,with texture homogeneity being closely linked to dune-type transitions.Specifically,homogeneous textures correspond to simple and stable forms such as barchans,while heterogeneous textures are associated with complex or composite dunes.The complexity,periodicity,and directionality of texture features are highly consistent with the spatial distribution of dunes.Validation using high-resolution remote sensing imagery(Sentinel-2)further confirms that the method effectively clusters similar dunes and distinguishes different dune types.Additionally,the dune classification results have a good correspondence with changes in near-surface wind regimes.Overall,the findings suggest that texture features derived from DEM can accurately capture the dynamic characteristics of dune morphology,offering a novel approach for automatic dune classification.Compared with traditional methods,the developed approach facilitates large-scale and high-precision dune mapping while reducing the workload of manual interpretation,thus advancing research on aeolian geomorphology.展开更多
Accurate reconstruction of understory terrain is essential for environmental monitoring and resource management.This study integrates 1:10,000 Digital Elevation Model,Global Ecosystem Dynamics Investigation(GEDI),and ...Accurate reconstruction of understory terrain is essential for environmental monitoring and resource management.This study integrates 1:10,000 Digital Elevation Model,Global Ecosystem Dynamics Investigation(GEDI),and AW3D30 Digital Surface Model data,combined with three machine learning algorithms—Random Forest(RF),Back Propagation Neural Network(BPNN),and Extreme Gradient Boosting(XGBoost)—to evaluate the performance of canopy height inversion and understory terrain reconstruction.The analysis emphasizes the impact of topographic and vegetation-related factors on model accuracy.Results reveal that slope is the most influential variable,contributing three to five times more to model performance than other features.In low-slope areas,understory terrain tends to be underestimated,whereas high-slope areas often result in overestimation.Moreover,the Normalized Difference Vegetation Index(NDVI)and land cover types,particularly forests and grasslands,significantly affect prediction accuracy,with model performance showing heightened sensitivity to vegetation characteristics in these regions.Among the models tested,XGBoost demonstrated superior performance,achieving a canopy height bias of-0.06 m,a root mean square error(RMSE)of 4.69 m for canopy height,and an RMSE of 9.82 m for understory terrain.Its ability to capture complex nonlinear relationships and handle high-dimensional data underlines its robustness.While the RF model exhibited strong stability and resistance to noise,its accuracy lagged slightly behind XGBoost.The BPNN model,by contrast,struggled in areas with complex terrain.This study offers valuable insights into feature selection and optimization in remote sensing applications,providing a reference framework for enhancing the accuracy and efficiency of environmental monitoring practices.展开更多
Considering the difficulty of integrating the depth points of nautical charts of the East China Sea into a global high-precision Grid Digital Elevation Model(Grid-DEM),we proposed a“Fusion based on Image Recognition(...Considering the difficulty of integrating the depth points of nautical charts of the East China Sea into a global high-precision Grid Digital Elevation Model(Grid-DEM),we proposed a“Fusion based on Image Recognition(FIR)”method for multi-sourced depth data fusion,and used it to merge the electronic nautical chart dataset(referred to as Chart2014 in this paper)with the global digital elevation dataset(referred to as Globalbath2002 in this paper).Compared to the traditional fusion of two datasets by direct combination and interpolation,the new Grid-DEM formed by FIR can better represent the data characteristics of Chart2014,reduce the calculation difficulty,and be more intuitive,and,the choice of different interpolation methods in FIR and the influence of the“exclusion radius R”parameter were discussed.FIR avoids complex calculations of spatial distances among points from different sources,and instead uses spatial exclusion map to perform one-step screening based on the exclusion radius R,which greatly improved the fusion status of a reliable dataset.The fusion results of different experiments were analyzed statistically with root mean square error and mean relative error,showing that the interpolation methods based on Delaunay triangulation are more suitable for the fusion of nautical chart depth of China,and factors such as the point density distribution of multiple source data,accuracy,interpolation method,and various terrain conditions should be fully considered when selecting the exclusion radius R.展开更多
Boundary extraction of watershed is an important step in forest landscape research. The boundary of the upriver wa-tershed of the Hunhe River in the sub-alpine Qingyuan County of eastern Liaoning Province, China was e...Boundary extraction of watershed is an important step in forest landscape research. The boundary of the upriver wa-tershed of the Hunhe River in the sub-alpine Qingyuan County of eastern Liaoning Province, China was extracted by digital elevation modeling (DEM) data in ArcInfo8.1. Remote sensing image of the corresponding region was applied to help modify its copy according to Enhanced Thematic Mapper (ETM) image抯 profuse geomorphological structure information. Both the DEM-dependent boundary and modified copy were overlapped with county map and drainage network map to visually check the effects of result. Overlap of county map suggested a nice extraction of the boundary line since the two layers matched precisely, which indicated the DEM-dependent boundary by program was effective and precise. Further upload of drainage network showed discrepancies between the boundary and the drainage network. Altogether, there were three sections of the extraction result that needed to correct. Compared with this extraction boundary, the modified boundary had a better match to the drainage network as well as to the county map. Comprehensive analysis demonstrated that the program extraction has generally fine precision in position and excels the digitized result by hand. The errors of the DEM-dependant extraction are due to the fact that it is difficult for program to recognize sections of complex landform especially altered by human activities, but these errors are discernable and adjustable because the spatial resolution of ETM image is less than that of DEM. This study result proved that application of remote sensing information could help obtain better result when DEM method is used in extraction of watershed boundary.展开更多
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 landfor...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.展开更多
Tropical mountainous areas not only provide substantial carbon storage and play an important role in global biological diversity, but also provide basic livelihood for a large number of poor ethnic minorities. However...Tropical mountainous areas not only provide substantial carbon storage and play an important role in global biological diversity, but also provide basic livelihood for a large number of poor ethnic minorities. However, there is no unified and explicit definition for mountainous areas. The local elevation range(LER) is a crucial structural parameter for delineating mountainous areas. However, current LER products are limited by the subjective selection of an optimum statistical window or coarser spatial resolution of topographical data. In this study, we presented an approach using thresholds for three topographic parameters, elevation, slope, and LER, derived from the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM) to redelineate the vast mountainous areas of mainland Southeast Asia(MSEA). The mean change-point analysis method was applied to determine the optimum statistical window of the 1 arc second(approximately 30 m)-resolution GDEM LER. The results showed that: First, the optimum statistical window is 38 × 38 cell units(width × height) in a rectangular neighborhood, or an area of about 1.30 km^2 for calculating GDEM LER in MSEA. Second, the LER of more than 80% of the area ranges from 30 m to 499 m in MSEA. The LERs in the northern and northwestern MSEA are greater than their counterparts in the south and east. Third, the area of the re-delineated mountainous areas was 83.52 × 10~4 km^2, about 38.71% of the total area. Spatially, the mountainous areas are mainly distributed in the north and northeast of MSEA. The re-delineated 30-m resolution map of the mountainous areas will serve as a topographical dataset for monitoring mountainrelated land surface changes in MSEA. The parameter-modified mountain extraction procedure can be expanded to delineate global mountainous areas.展开更多
基金supported by the(i)Commonwealth Scholarship Commission and the Foreign,Commonwealth and Development Office in the UK[Grant number NGCN-2021-239](ii)University of Cape Town Postgraduate Funding Office.
文摘Validation studies of global Digital Elevation Models(DEMs)in the existing literature are limited by the diversity and spread of landscapes,terrain types considered and sparseness of groundtruth.Moreover,there are knowledge gaps on the accuracy variations in rugged and complex landscapes,and previous studies have often not relied on robust internal and external validation measures.Thus,there is still only partial understanding and limited perspective of the reliability and adequacy of global DEMs for several applications.In this study,we utilize a dense spread of LiDAR groundtruth to assess the vertical accuracies of four medium-resolution,readily available,free-access and global coverage 1 arc-second(30 m)DEMs:NASADEM,ASTER GDEM,Copernicus GLO-30,and ALOS World 3D(AW3D).The assessment is carried out at landscapes spread across Cape Town,Southern Africa(urban/industrial,agricultural,mountain,peninsula and grassland/shrubland)and forested national parks in Gabon,Central Africa(low-relief tropical rainforest and high-relief tropical rainforest).The statistical analysis is based on robust accuracy metrics that cater for normal and non-normal elevation error distribution,and error ranking.In Cape Town,Copernicus DEM generally had the least vertical error with an overall Mean Error(ME)of 0.82 m and Root Mean Square Error(RMSE)of 2.34 m while ASTER DEM had the poorest performance.However,ASTER GDEM and NASADEM performed better in the low-relief and high-relief tropical forests of Gabon.Generally,the DEM errors have a moderate to high positive correlation in forests,and a low to moderate positive correlation in mountains and urban areas.Copernicus DEM showed superior vertical accuracy in forests with less than 40%tree cover,while ASTER and NASADEM performed better in denser forests with tree cover greater than 70%.This study is a robust regional assessment of these global DEMs.
基金supported in part by the National Natural Science Foundation of China under grant of 42090012in part by the project supported by the Open Fund of Hubei Luojia Laboratory(220100009)+3 种基金in part by 03 special research and 5G project of Jiangxi province in China(20212ABC03A09)Zhuhai industry university research cooperation project of China(ZH22017001210098PWC)Sichuan Science and Technology Program(2022YFN0031)Zhizhuo Research Fund on Spatial-Temporal Artificial Intelligence(Grant No.ZZJJ202202).
文摘High-quality height reference data are embedded in the accuracy verification processes of most remote sensing terrain applications.The Ice,Cloud,and Land elevation Satellite 2(ICESat-2)/ATL08 terrain product has shown promising results for estimating ground heights,but it has not been fully evaluated.Hence,this study aims to assess and enhance the accuracy of the ATL08 terrain product as a height reference for the newest versions of the Advanced Spaceborne Thermal Emission and Reflection Radiometer(ASTER),the Shuttle Radar Topography Mission(SRTM),and TanDEM-X(TDX)DEMs over vegetated mountainous areas.We used uncertainty-based filtering method for the ATL08 strong and weak beams to enhance their accuracy.Then,the results were evaluated against a reference airborne LiDAR digital terrain model(DTM),by selecting 10,000 points over the entire area and comparing the accuracy of ASTER,SRTM,and TDX DEMs assessed by the LiDAR DTM to the accuracy of the ASTER,SRTM,and TDX DEMs assessed by the ATL08 strong beams,weak beams,and all beams.We also detected the impact of the terrain aspect,slope,and land cover types on the accuracy of the ATL08 terrain elevations and their relationship with height errors and uncertainty.Our findings show the accuracy of the ATL08 strong beams was enhanced by 43.91%;while the weak beams accuracy was enhanced by 74.05%.Furthermore,slope strongly influenced ATL08 height errors and height uncertainty;especially on the weak beams.The errors induced by the slope significantly decreased when the uncertainty levels were reduced to<20 m.The evaluations of ASTER,SRTM,and TDX DEMs by ATL08 strong and weak beams are close to those assessed by LiDAR DTM points within 0.6 m for the strong beams.These findings indicate that ATL08 strong beams can be used as a height reference over vegetated mountainous regions.
基金supported by the Professional Development Award of the University of Tennessee
文摘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.
基金supported by the National Natural Science Foundation of China(Grant Nos.41471316,41401456)A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions-PAPD(Grant No.164320H101)+1 种基金Major University Science Research Project of Jiangsu Province(Grant No.13KJA170001)the financial support provided by the PhD Scholarship from Eurasic Pacific Uninet for collaboration research in Austria
文摘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.
基金partially supported by JSPS KAKENHI(Grant No.16H03153)the Limestone Association of Japan。
文摘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.
基金financial support from the National Natural Science Foundation of China(No.40201021)the Zhejiang Natural Science Foundation of China(M403040).
文摘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.
文摘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.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40930531, 41171320)the National High Technology Research and Development Program of China (Grant No. 2011AA120303)Open Foundation of State Key Laboratory of Resources and Environmental Information System (Grant No. 2010KF0002SA)
文摘The influence of pre-quaternary underlying terrain on the formation of loess landforms, i.e., the geomorphological inheritance issue, is a focus in studies of loess landforms. On the basis of multi-source information, we used GIS spatial analysis methods to construct a simulated digital elevation model of a pre-quaternary paleotopographic surface in a severe soil erosion area of the Loess Plateau. To reveal the spatial relationship between underlying paleotopography and modern terrain, an XY scatter diagram, hypsometric curve, gradient and concavity of terrain profiles are used in the experiments. The experiments show that the altitude, gradient and concavity results have significant linear positive correlation between both terrains, which shows a relatively strong landform inheritance relationship, particularly in the intact and complete loess deposit areas. Despite the current surface appearing somewhat changed from the original shape of the underlying terrain under different erosion forces, we reveal that the modern terrain generally smoothes the topographic relief of underlying terrain in the loess deposition process. Our results deepen understanding of the characteristics of geomorphological inheritance in the formation and evolution of loess landforms.
基金The authors gratefully acknowledge the science teams of NASA High Mountain Asia 8-meter DEM and NASA ICESat-2 for providing access to the data.This work was conducted with the infrastructure provided by the National Remote Sensing Centre(NRSC),for which the authors were indebted to the Director,NRSC,Hyderabad.We acknowledge the continued support and scientific insights from Mr.Rakesh Fararoda,Mr.Sagar S Salunkhe,Mr.Hansraj Meena,Mr.Ashish K.Jain and other staff members of Regional Remote Sensing Centre-West,NRSC/ISRO,Jodhpur.The authors want to acknowledge Dr.Kamal Pandey,Scientist,IIRS,Dehradun,for sharing field-level information about the Auli-Joshimath.This research did not receive any specific grant from funding agencies in the public,commercial,or not-for-profit sectors.
文摘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-Xizang,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.
基金central Yunnan Province(1:50,000)Chuxiong City,central Yunnan Province(Grant/Award Numbers:DD20220987)the National Natural Science Foundation of China(Grant/Award Numbers:41972118).
文摘The Longchuan River basin lies within the China Sichuan-Yunnan rhomboid block.The NS-trending Yuanmou-Lvzhi River Fault(YLF),NW-trending Chuxiong-Nanhua Fault(CNF)and Shiyang-Huoshaotun Fault(HSF)are found within the basin.The nature of the faults is complex,and the tectonic activity distribution characteristics require further clarification.By extraction from a digital elevation model,the measured longitudinal profile and the geomorphic indices of the Longchuan River,basin showed a stream-length gradient index(SL)of 49–650,hypsometric integral(HI)of 0.27–0.58,drainage basin asymmetry factor(AF)of 3.29–27.47,basin shape index(BS)of 0.87–2.75,valley floor width-to-height ratio(VF)of 0.06–5.40,and evaluation of relative tectonic activity(Iat)of 1.6–2.6.Results showed that river morphology and geomorphological indices in the Longchuan River basin were influenced by tectonic activity,bedrock lithology,climatic conditions,and development time,with tectonic activity playing a dominant role.The relative tectonic activity of the Longchuan River basin was zoned,with a gradual increase in relative tectonic activity from the south to the north.That the slip fault zone primarily controls the tectonic deformation of the Longchuan River basin in central Yunnan and the dynamics of the central Yunnan massif are consistent with the“rigid block lateral extrusion”1model.
文摘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.
基金supported by the National Natural Science Foundation of China(grant 41901088)the China Postdoctoral Science Foundation(grant 2020M670423)+2 种基金supported by the National Natural Science Foundation of China(grant 41530748)the second Tibetan Plateau Scientific Expedition and Research Program(grant 2019QZKK0202)the 13th Five-year Informatization Plan of Chinese Academy of Sciences(grant XXH13505-06)。
文摘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.
基金supported by the National Key Research and Development Project of China(No.2023YFC3007303)the Open Research Project of the Hubei Key Laboratory of Intelligent Geo-Information Processing(No.KLIGIP-2019B08)。
文摘0 INTRODUCTION.The global availability of digital elevation model(DEM)data,such as 90-m Shuttle Radar Topography Mission(SRTM)DEM and 30-m Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM),has been extensively utilized in morphotectonic analyses(e.g.,Wang et al.,2024;Cheng et al.,2018;Pérez-Pe?a et al.,2010;El Hamdouni et al.,2008).
文摘Geomorphometric modeling and mapping of Antarctic oases are promising for obtaining new quantitative knowledge about the topography of these unique landscapes and for the further use of morphometric information in Antarctic research.Within the framework of a project to create a thematic physical-geographical scientific reference geomorphometric atlas of ice-free areas of Antarctica,we performed geomorphometric modeling and mapping of the Bunger Hills(Knox Coast,Wilkes Land,East Antarctica),one of the largest Antarctic oases.By processing a fragment of the Reference Elevation Model of Antarctica(REMA)covering the Bunger Hills and adjacent glaciers,we created,for the first time,a series of 37 medium-to large-scale maps of nine of the most scientifically important morphometric variables(i.e.,slope gradient,slope aspect,vertical curvature,horizontal curvature,maximal curvature,minimal curvature,catchment area,topographic wetness index,and stream power index).The morphometric maps describe the topography of the Bunger Hills in a quantitative,rigorous,and reproducible manner.New morphometric data can be useful for further geological,geomorphological,glaciological,ecological,and hydrological studies of this Antarctic oasis.
基金supported by the National Natural Science Foundation of China(42271421).
文摘Texture analysis methods offer substantial advantages and potential in examining macro-topographic features of dunes.Despite these advantages,comprehensive approaches that integrate digital elevation model(DEM)with quantitative texture features have not been fully developed.This study introduced an automatic classification framework for dunes that combines texture and topographic features and validated it through a typical coastal aeolian landform,namely,dunes in the Namib Desert.A three-stage approach was outlined:(1)segmentation of dune units was conducted using digital terrain analysis;(2)six texture features(angular second moment,contrast,correlation,variance,entropy,and inverse difference moment)were extracted from the gray-level co-occurrence matrix(GLCM)and subsequently quantified;and(3)texture–topographic indices were integrated into the random forest(RF)model for classification.The results show that the RF model fused with texture features can accurately identify dune morphological characteristics;through accuracy evaluation and remote sensing image verification,the overall accuracy reaches 78.0%(kappa coefficient=0.72),outperforming traditional spectral-based methods.In addition,spatial analysis reveals that coastal dunes exhibit complex texture patterns,with texture homogeneity being closely linked to dune-type transitions.Specifically,homogeneous textures correspond to simple and stable forms such as barchans,while heterogeneous textures are associated with complex or composite dunes.The complexity,periodicity,and directionality of texture features are highly consistent with the spatial distribution of dunes.Validation using high-resolution remote sensing imagery(Sentinel-2)further confirms that the method effectively clusters similar dunes and distinguishes different dune types.Additionally,the dune classification results have a good correspondence with changes in near-surface wind regimes.Overall,the findings suggest that texture features derived from DEM can accurately capture the dynamic characteristics of dune morphology,offering a novel approach for automatic dune classification.Compared with traditional methods,the developed approach facilitates large-scale and high-precision dune mapping while reducing the workload of manual interpretation,thus advancing research on aeolian geomorphology.
基金funded by the National Key Research and Development Program(Grants No.2023YFE0207900)。
文摘Accurate reconstruction of understory terrain is essential for environmental monitoring and resource management.This study integrates 1:10,000 Digital Elevation Model,Global Ecosystem Dynamics Investigation(GEDI),and AW3D30 Digital Surface Model data,combined with three machine learning algorithms—Random Forest(RF),Back Propagation Neural Network(BPNN),and Extreme Gradient Boosting(XGBoost)—to evaluate the performance of canopy height inversion and understory terrain reconstruction.The analysis emphasizes the impact of topographic and vegetation-related factors on model accuracy.Results reveal that slope is the most influential variable,contributing three to five times more to model performance than other features.In low-slope areas,understory terrain tends to be underestimated,whereas high-slope areas often result in overestimation.Moreover,the Normalized Difference Vegetation Index(NDVI)and land cover types,particularly forests and grasslands,significantly affect prediction accuracy,with model performance showing heightened sensitivity to vegetation characteristics in these regions.Among the models tested,XGBoost demonstrated superior performance,achieving a canopy height bias of-0.06 m,a root mean square error(RMSE)of 4.69 m for canopy height,and an RMSE of 9.82 m for understory terrain.Its ability to capture complex nonlinear relationships and handle high-dimensional data underlines its robustness.While the RF model exhibited strong stability and resistance to noise,its accuracy lagged slightly behind XGBoost.The BPNN model,by contrast,struggled in areas with complex terrain.This study offers valuable insights into feature selection and optimization in remote sensing applications,providing a reference framework for enhancing the accuracy and efficiency of environmental monitoring practices.
基金Supported by the National Key R&D Program of China (No.2023YFC3008100)the National Natural Science Foundation of China (No.U23A2033)
文摘Considering the difficulty of integrating the depth points of nautical charts of the East China Sea into a global high-precision Grid Digital Elevation Model(Grid-DEM),we proposed a“Fusion based on Image Recognition(FIR)”method for multi-sourced depth data fusion,and used it to merge the electronic nautical chart dataset(referred to as Chart2014 in this paper)with the global digital elevation dataset(referred to as Globalbath2002 in this paper).Compared to the traditional fusion of two datasets by direct combination and interpolation,the new Grid-DEM formed by FIR can better represent the data characteristics of Chart2014,reduce the calculation difficulty,and be more intuitive,and,the choice of different interpolation methods in FIR and the influence of the“exclusion radius R”parameter were discussed.FIR avoids complex calculations of spatial distances among points from different sources,and instead uses spatial exclusion map to perform one-step screening based on the exclusion radius R,which greatly improved the fusion status of a reliable dataset.The fusion results of different experiments were analyzed statistically with root mean square error and mean relative error,showing that the interpolation methods based on Delaunay triangulation are more suitable for the fusion of nautical chart depth of China,and factors such as the point density distribution of multiple source data,accuracy,interpolation method,and various terrain conditions should be fully considered when selecting the exclusion radius R.
基金This work was supported by Knowledge Innovation Pro-gram Chinese Academy of Sciences (No. KZCX2-SW-320-3 & KZCX3-SW-425).
文摘Boundary extraction of watershed is an important step in forest landscape research. The boundary of the upriver wa-tershed of the Hunhe River in the sub-alpine Qingyuan County of eastern Liaoning Province, China was extracted by digital elevation modeling (DEM) data in ArcInfo8.1. Remote sensing image of the corresponding region was applied to help modify its copy according to Enhanced Thematic Mapper (ETM) image抯 profuse geomorphological structure information. Both the DEM-dependent boundary and modified copy were overlapped with county map and drainage network map to visually check the effects of result. Overlap of county map suggested a nice extraction of the boundary line since the two layers matched precisely, which indicated the DEM-dependent boundary by program was effective and precise. Further upload of drainage network showed discrepancies between the boundary and the drainage network. Altogether, there were three sections of the extraction result that needed to correct. Compared with this extraction boundary, the modified boundary had a better match to the drainage network as well as to the county map. Comprehensive analysis demonstrated that the program extraction has generally fine precision in position and excels the digitized result by hand. The errors of the DEM-dependant extraction are due to the fact that it is difficult for program to recognize sections of complex landform especially altered by human activities, but these errors are discernable and adjustable because the spatial resolution of ETM image is less than that of DEM. This study result proved that application of remote sensing information could help obtain better result when DEM method is used in extraction of watershed boundary.
基金Under the auspices of National Youth Science Foundation of China(No.41001294)Key Project of National Natural Science Foundation of China(No.40930531)Research Fund of State Key Laboratory Resources and Environment Information System(No.2010KF0002SA)
文摘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.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDA20010203)
文摘Tropical mountainous areas not only provide substantial carbon storage and play an important role in global biological diversity, but also provide basic livelihood for a large number of poor ethnic minorities. However, there is no unified and explicit definition for mountainous areas. The local elevation range(LER) is a crucial structural parameter for delineating mountainous areas. However, current LER products are limited by the subjective selection of an optimum statistical window or coarser spatial resolution of topographical data. In this study, we presented an approach using thresholds for three topographic parameters, elevation, slope, and LER, derived from the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM) to redelineate the vast mountainous areas of mainland Southeast Asia(MSEA). The mean change-point analysis method was applied to determine the optimum statistical window of the 1 arc second(approximately 30 m)-resolution GDEM LER. The results showed that: First, the optimum statistical window is 38 × 38 cell units(width × height) in a rectangular neighborhood, or an area of about 1.30 km^2 for calculating GDEM LER in MSEA. Second, the LER of more than 80% of the area ranges from 30 m to 499 m in MSEA. The LERs in the northern and northwestern MSEA are greater than their counterparts in the south and east. Third, the area of the re-delineated mountainous areas was 83.52 × 10~4 km^2, about 38.71% of the total area. Spatially, the mountainous areas are mainly distributed in the north and northeast of MSEA. The re-delineated 30-m resolution map of the mountainous areas will serve as a topographical dataset for monitoring mountainrelated land surface changes in MSEA. The parameter-modified mountain extraction procedure can be expanded to delineate global mountainous areas.
