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1.
An iterative procedure that implements the classification of continuous topography as a problem in digital image-processing automatically divides an area into categories of surface form; three taxonomic criteria–slope gradient, local convexity, and surface texture–are calculated from a square-grid digital elevation model (DEM). The sequence of programmed operations combines twofold-partitioned maps of the three variables converted to greyscale images, using the mean of each variable as the dividing threshold. To subdivide increasingly subtle topography, grid cells sloping at less than mean gradient of the input DEM are classified by designating mean values of successively lower-sloping subsets of the study area (nested means) as taxonomic thresholds, thereby increasing the number of output categories from the minimum 8 to 12 or 16. Program output is exemplified by 16 topographic types for the world at 1-km spatial resolution (SRTM30 data), the Japanese Islands at 270 m, and part of Hokkaido at 55 m. Because the procedure is unsupervised and reflects frequency distributions of the input variables rather than pre-set criteria, the resulting classes are undefined and must be calibrated empirically by subsequent analysis. Maps of the example classifications reflect physiographic regions, geological structure, and landform as well as slope materials and processes; fine-textured terrain categories tend to correlate with erosional topography or older surfaces, coarse-textured classes with areas of little dissection. In Japan the resulting classes approximate landform types mapped from airphoto analysis, while in the Americas they create map patterns resembling Hammond's terrain types or surface-form classes; SRTM30 output for the United States compares favorably with Fenneman's physical divisions. Experiments are suggested for further developing the method; the Arc/Info AML and the map of terrain classes for the world are available as online downloads.  相似文献   

2.
Traditionally, forest inventory and ecosystem mapping at local to regional scales rely on manual interpretation of aerial photographs, based on standardized, expert-driven classification schemes. These current approaches provide the information needed for forest ecosystem management but constrain the thematic and spatial resolution of mapping and are infrequently repeated. The goal of this research was to demonstrate the utility of an unsupervised, quantitative technique based on Light Detection And Ranging (LiDAR) data and multi-spectral satellite imagery for mapping local-scale ecosystems over a heterogeneous landscape of forested and non-forested ecosystems. We derived a range of metrics characterizing local terrain and vegetation from LiDAR and RapidEye imagery for Calvert and Hecate Islands, British Columbia. These metrics were used in a cluster analysis to classify and quantitatively characterize ecological units across the island. A total of 18 clusters were derived. The clusters were attributed with quantitative summary statistics from the remotely sensed data inputs and contextualized through comparison to ecological units delineated in a traditional expert-driven mapping method using aerial photographs. The 18 clusters describe ecosystems ranging from open shrublands to dense, productive forest and include a riparian zone and many wetter and wetland ecosystems. The clusters provide detailed, spatially-explicit information for characterizing the landscape as a mosaic of units defined by topography and vegetation structure. This study demonstrates that using various types of remotely sensed data in a quantitative classification can provide scientists and managers with multivariate information unique from that which results from traditional, expert-based ecosystem mapping methods.  相似文献   

3.
不同地貌类型水土流失区的地面坡谱分析   总被引：3，自引：0，他引：3  
坡度是影响水土流失的重要因素之一,然而坡度作为一种微观定量因子,并不能有效表达区域地形的总体特征。本研究采用地面坡谱统计分析方法,研究地形对水土流失的影响,并以福建省宁化县为例,选取5个不同地貌类型的典型水土流失区,通过均值、中位数等7个统计值对坡谱特征进行刻画,并与研究区的水土流失程度进行拟合分析。研究结果表明：1）丘陵和山地地貌类型分别具有特定形态的坡谱,反映了不同地貌类型的地形起伏差异,以及地表的破碎程度;2）从坡谱统计值与其水土流失程度商值的拟合曲线上,可以看出宁化县水土流失程度除与坡谱锋态不相关外,与其他统计值均相关,并且在水土流失越轻区域,水土流失程度对坡谱统计值的微小变化越敏感;3）坡谱蕴含丰富的地貌信息,有望较准确地量化地形对水土流失影响的程度。  相似文献   

4.
This paper documents resolution dependencies in terrain analysis and describes how they vary across landform location. Six terrain attributes were evaluated as a function of DEM resolution—slope, plan curvature, profile curvature, north–south slope orientation, east–west slope orientation, and topographic wetness index. The research highlights the effect of varying spatial resolution through a spatial sampling/resampling scheme while maintaining sets of indexed sample points at various resolutions. Tested sample points therefore coincide exactly between two directly compared resolutions in terms of their location and elevation value. An unsupervised landform classification procedure based on statistical clustering algorithms was employed to define landform classes in a reproducible manner. Correlation and regression analyses identified sensitive and consistent responses for each attribute as resolution was changed, although the tested terrain attributes responded in characteristically different ways. These responses displayed distinguishable patterns among various landform classes, a conclusion that was further verified by a series of two‐sample, two‐tailed t‐tests.  相似文献   

5.
面向地貌学本源的数字地形分析研究进展与展望   总被引：5，自引：2，他引：3  
数字地形分析（DTA）是地理信息科学（GIS）研究的热点。但是,当前基于数字高程模型（DEM）的数字地形分析在地貌学研究中存在重形态轻机理、重现象轻过程、重地上轻地下等问题,急需从单一的地貌形态分析,迈向面向成因、过程与机理等地貌学本源问题的研究转变。据此,本文系统梳理了面向地貌学本源的数字地形分析的相关研究现状,并从地貌学本源认识、地貌形态建模、地形因子提取、以及其他地形分析方法等研究进行了系统的回顾、梳理与分析。研究表明,基于DEM的数字地形分析虽具有地貌特征分析的潜力与优势,但是,数字地形分析存在数据表达与分析模式上的先天缺陷,亟待通过基础理论与关键技术的突破,实现理论与方法的创新发展,实现从“坡面”走向“区域”,从“形态”走向“过程”,从“地形”走向“地貌”。而当今地球系统科学的研究发展态势也到了数字地形分析研究从重视地貌形态走向揭示地貌学本源的关键阶段。因此,本文从DEM数据模型增值、地形因子及其地形空间关系、以及宏观地形分析等侧面展望了面向地貌学本源的数字地形分析研究。当今基于DEM的数字地形分析研究,正像当前的GIS是否能够真正支撑地理学发展一样,已经处于一个非常关键的十字路口。面向地貌学本源的数字地形分析研究思路可望成为地理信息科学领域理论与方法创新的一次重要探索与实践。  相似文献   

6.
We describe a method of morphometric characterisation of landform from digital elevation models (DEMs). The method is implemented first by classifying every location into morphometric classes based on the mathematical shape of a locally fitted quadratic surface and its positional relationship with the analysis window. Single‐scale fuzzy terrain indices of peakness, pitness, passness, ridgeness, and valleyness are then calculated based on the distance of the analysis location from the ideal cases. These can then be combined into multi‐scale terrain indices to summarise terrain information across different operational scales. The algorithm has four characteristics: (1) the ideal cases of different geomorphometric features are simply and clearly defined; (2) the output is spatially continuous to reflect the inherent fuzziness of geomorphometric features; (3) the output is easily combined into a multi‐scale index across a range of operational scales; and (4) the standard general morphometric parameters are quantified as the first and second order derivatives of the quadratic surface. An additional benefit of the quadratic surface is the derivation of the R 2 goodness of fit statistic, which allows an assessment of both the reliability of the results and the complexity of the terrain. An application of the method using a test DEM indicates that the single‐ and multi‐scale terrain indices perform well when characterising the different geomorphometric features.  相似文献   

7.
Natural hazards are mostly related to the activation of combined geomorphological and geological processes that control landform development. The study area is located in the NE part of Peloponnese (Corinthos prefecture). It is a typical agricultural area with intense relief, the result of active tectonics and important human intervention. This study demonstrates the benefits from the synergism of SAR data (ERS-2) and optical data (SPOT2-XS) in order to highlight the possible natural-hazardprone areas. These data give different and complementary information since the radar signal depends mostly on topography, surface roughness and soil moisture, whereas the visible/infrared channels provide spectral information mostly on vegetation and land use/cover. The application presented here was focused on the enhancement of the high erosion risk areas, the improvement of the terrain interpretation, the mapping and highlighting of the landform morphology, and a more accurate determination of the main factors that control the flooding risk of Corinthos town.  相似文献   

8.
Landslide inventory maps are necessary for assessing landslide hazards and addressing the role slope stability plays in landscape evolution over geologic timescales. However, landslide inventory maps produced with traditional methods — aerial photograph interpretation, topographic map analysis, and field inspection — are often subjective and incomplete. The increasing availability of high-resolution topographic data acquired via airborne Light Detection and Ranging (LiDAR) over broad swaths of terrain invites new, automated landslide mapping procedures. We present two methods of spectral analysis that utilize LiDAR-derived digital elevation models of the Puget Sound lowlands, Washington, and the Tualatin Mountains, Oregon, to quantify and automatically map the topographic signatures of deep-seated landslides. Power spectra produced using the two-dimensional discrete Fourier transform and the two-dimensional continuous wavelet transform identify the characteristic spatial frequencies of deep-seated landslide morphologic features such as hummocky topography, scarps, and displaced blocks of material. Spatial patterns in the amount of spectral power concentrated in these characteristic frequency bands highlight past slope instabilities and allow the delineation of landslide terrain. When calibrated by comparison with detailed, independently compiled landslide inventory maps, our algorithms correctly classify an average of 82% of the terrain in our five study areas. Spectral analysis also allows the creation of dominant wavelength maps, which prove useful in analyzing meter-scale topographic expressions of landslide mechanics, past landslide activity, and landslide-modifying geomorphic processes. These results suggest that our automated landslide mapping methods can create accurate landslide maps and serve as effective, objective, and efficient tools for digital terrain analysis.  相似文献   

9.
天山北麓流域面积高度积分特征及其构造意义   总被引：2，自引：0，他引：2  
提取了天山北麓河流水系流域的常规地貌计量指标（盆地大小、面积和高差）以及面积高度积分,通过对流域面积高度积分曲线形态特征、面积高度积分值的分析,结合区域地质构造活动,探讨了面积高度积分对板内再生造山带新构造活动的指示意义以及天山北麓流域的地貌发育过程。研究表明,北天山流域的次集水盆地面积高度积分与次集水盆地的面积和高差都没有相关性,堆积作用和轻微构造抬升作用都会影响冲积扇区次集水盆地,使其面积高度积分值偏高。河流面积高度积分曲线形态和面积高度积分值在空间分布上的差异,反映了天山北麓3排逆断裂褶皱带的不同的构造活动特征。面积高度积分曲线的循环形态特征,揭示了强烈构造运动与河流剥蚀作用影响面积高度曲线形态发育的动态演绎过程。  相似文献   

10.
The analysis of the spatial structure of animal communities requires spatial data to determine the distribution of individuals and their limiting factors. New technologies like very precise GPS as well as satellite imagery and aerial photographs of very high spatial resolution are now available. Data from airborne LiDAR (Light Detection and Ranging) sensors can provide digital models of ground and vegetation surfaces with pixel sizes of less than 1 m. We present the first study in terrestrial herpetology using LiDAR data. We aim to identify the spatial patterns of a community of four species of lizards (Lacerta schreiberi, Timon lepidus, Podarcis bocagei, and P. hispanica), and to determine how the habitat is influencing the distribution of the species spatially. The study area is located in Northern Portugal. The position of each lizard was recorded during 16 surveys of 1 h with a very precise GPS (error < 1 m). LiDAR data provided digital models of surface, terrain, and normalised height. From these data, we derived slope, ruggedness, orientation, and hill-shading variables. We applied spatial statistics to determine the spatial structure of the community. We computed Maxent ecological niche models to determine the importance of environmental variables. The community and its species presented a clustered distribution. We identified 14 clusters, composed of 1–3 species. Species records showed two distribution patterns, with clusters associated with steep and flat areas. Cluster outliers had the same patterns. Juveniles and subadults were associated with areas of low quality, while sexes used space in similar ways. Maxent models identified suitable habitats across the study area for two species and in the flat areas for the other two species. LiDAR allowed us to understand the local distributions of a lizard community. Remotely sensed data and LiDAR are giving new insights into the study of species ecology. Images of higher spatial resolutions are necessary to map important factors such as refuges.  相似文献   

11.
Hypsometric curves and integrals are effective tools for rapid quantitative assessments of topography. High‐resolution digital terrain models derived from airborne LiDAR data have been analysed to study the hypsometry of small headwater rock basins (drainage areas up to 0.13 km2) in three study areas in the Dolomites (Eastern Alps) that have similar lithologies and climatic conditions. Hypsometric curves in the studied rocky headwaters display a variety of shapes and present remarkable differences between neighbouring basins. Hypsometric integrals show generally high values in the three study areas (>0.42, mean values between 0.51 and 0.65). The extent of the scree slopes located at the foot of rock basins in the three study areas is larger in the area with lower hypsometric integrals and indicates consistency between the development of basin erosion, which is shown by the hypsometric integral, and debris yield, represented by the extent of scree slope. No clear relations were observed between the hypsometric integrals and basin area and shape. When extending the analysis to larger basins, which encompass rocky headwaters and downslope soil‐mantled slopes, a negative correlation is found between the hypsometric integral and catchment area, suggesting that the scale independency of the hypsometric integral occurs essentially in headwater rock basins. Geomorphometric indices (residual relief and surface roughness) have contributed to interpreting the variability of surface morphology, which is related to the geo‐structural complexity of the catchments.  相似文献   

12.
S. Rayburg  M. Thoms  M. Neave 《Geomorphology》2009,106(3-4):261-270
It can be challenging to accurately determine the topography of physically complex landscapes in remote areas. Ground-based surveys can be difficult, time consuming and may miss significant elements of the landscape. This study compares digital elevation models (DEMs) generated from three different data sources, of the physically complex Narran Lakes Ecosystem, a major floodplain wetland ecosystem in Australia. Topographic surfaces were generated from an airborne laser altimetry (LiDAR) survey, a ground-based differential GPS (DGPS) survey containing more than 20,000 points, and the 9″ DEM of Australia. The LiDAR- and DGPS-derived data generated a more thorough DEM than the 9″ DEM; however, LiDAR generated a surface topography that yielded significantly more detail than the DGPS survey, with no noticeable loss of elevational accuracy. Both the LiDAR- and the DGPS-derived DEMs compute the overall surface area and volume of the largest floodplain lake within the system to within 1% of each other. LiDAR is shown to be a highly accurate and robust technique for acquiring large quantities of topographic data, even in locations that are unsuitable for ground surveying and where the overall landscape is of exceptionally low relief. The results of this study highlight the potential for LiDAR surveys in the accurate determination of the topography of floodplain wetlands. These data can form an important component of water resource management decisions, particularly where environmental water allocations for these important ecosystems need to be determined.  相似文献   

13.
Multi-scale landform characterization   总被引：4，自引：0，他引：4  
Jochen Schmidt  Robbie Andrew 《Area》2005,37(3):341-350
One fundamental objective in geomorphometry is to extract signatures of geomorphologic processes on different spatial scales from digital terrain models (DTMs) and to describe the complexity of landforms as the synthesis of those individual imprints. We present an approach for characterizing land surfaces on multiple, spatially varying local scales. We approximate terrain surfaces locally to calculate surface derivatives at different window sizes. Local scale behaviour diagrams are used to define dominant scale ranges and multiple curvatures for each surface point. Multi-scale landform analysis leads to improved models of surface derivatives and new landform classifications, applicable in geomorphology, soil science and hydrology.  相似文献   

14.
Developing approaches to automate the analysis of the massive amounts of data sent back from the Moon will generate significant benefits for the field of lunar geomorphology.In this paper,we outline an automated method for mapping lunar landforms that is based on digital terrain analysis.An iterative self-organizing(ISO)cluster unsupervised classification enables the automatic mapping of landforms via a series of input raster bands that utilize six geomorphometric parameters.These parameters divide landforms into a number of spatially extended,topographically homogeneous segments that exhibit similar terrain attributes and neighborhood properties.To illustrate the applicability of our approach,we apply it to three representative test sites on the Moon,automatically presenting our results as a thematic landform map.We also quantitatively evaluated this approach using a series of confusion matrices,achieving overall accuracies as high as 83.34% and Kappa coefficients(K)as high as 0.77.An immediate version of our algorithm can also be applied for automatically mapping large-scale lunar landforms and for the quantitative comparison of lunar surface morphologies.  相似文献   

15.
Regional automatic segmentation – automatic terrain segmentation according to terrain features – is significant for modern geographical analysis. We propose a new approach of terrain region segmentation based on the region growth method. This method features actual runoff nodes as seed points. The corresponding growth threshold is defined based on statistical analysis of quantitative indexes of topographic features. Terrain segmentation of some regions is completed using the growth threshold. The corresponding edge boundaries of different terrain regions are extracted by image processing. Thus, the automatic segmentation of the terrain region is realized by the edge boundary. The application of the method to a typical Chinese loess landform area and automatic segmentation of three types of terrain regions – gully interfluve land, gully slope land, and gully groove land – are achieved by analyzing characteristics of the curvature structure of surface profiles. Segmentation results, compared with results of visual interpretation from a high-precision digital orthophoto map, show an average accuracy of segmentation of 93.51%. Topographic factor features of segmentation results are statistically analyzed. This study presents an effective and practical approach for segmenting terrain regions. This approach may be incorporated into the theory and method system of digital terrain analysis.  相似文献   

16.
中国地貌区划新论   总被引：12，自引：3，他引：9  
地貌区划是研究自然环境空间分异的基础,在区域地貌研究中具有十分重要的地位.本文分析总结了国内外地貌区划的相关研究成果,系统探讨了地貌区划的具体步骤与方法、地貌区划的原则、各级地貌区划的依据和标准,提出地貌类型组合和地貌成因类型的基本异同是各级地貌区划的依据.本文以中国1:400 万地貌图等新资料为基础,应用GIS 方法,结合中国三大地貌阶梯及其内部地貌格局的特点,通过分析我国各地基本地貌类型组合的差异及其形成原因,将中国地貌区划分为东部低山平原大区、东南低中山地大区、中北中山高原大区、西北高中山盆地大区、西南亚高山地大区和青藏高原大区6 个地貌大区,并分别简要论述了各大区的地貌特征.各大区内部又据次级基本地貌类型和地貌成因类型及其组合差异进一步分区,全国共划分了38个地貌区.  相似文献   

17.
龙虎山丹霞地貌"旅游景观价值-游客审美感知"探讨   总被引：2，自引：1，他引：1  
通过对龙虎山丹霞地貌类型及其地质遗迹、人文景观的分析,按景区空间组合及代表性景观构建了旅游景观谱系。对这些景观进行评价和游客感知度调查,形成游客感知率与景观评价值矩阵,并用坐标法将矩阵划分为4个象限,分析其间的耦合性、差异性和产生机理。结果显示,总体上符合景观赋分值高、游客感知度高,景观赋分值低、游客感知度低的规律,但对一些典型地质遗迹,专家的评价与游客的感知度相差较大。游客仍以直观的山水审美为主,对其蕴含的科学性认知不够。地质遗迹科考产品和科普产品开发不足,尚未形成大众产品。比较不同游客群体的审美感知差异,为旅游产品的市场细分提供依据,并提出丹霞地貌景区建设建议。  相似文献   

18.
Errors in LiDAR-derived shrub height and crown area on sloped terrain   总被引：1，自引：0，他引：1  
This study developed and tested four methods for shrub height measurements with airborne LiDAR data in a semiarid shrub-steppe in southwestern Idaho, USA. Unique to this study was the focus of sagebrush height measurements on sloped terrain. The study also developed one of the first methods towards estimating crown area of sagebrush from LiDAR. Both sagebrush height and crown area were underestimated by LiDAR. Sagebrush height was estimated to within ± 0.26-0.32 mm (two standard deviations of standard error). Crown area was underestimated by a mean of 49%. Further, hillslope had a relatively low impact on sagebrush height and crown area estimation. From a management perspective, estimation of individual shrubs over large geographic areas can be accomplished using a 0.5 m rasterized vegetation height derivative from LiDAR. While the underestimation of crown area is substantial, we suggest that this underestimation would improve with higher LiDAR point density (>4 points/m2). Further studies can estimate shrub biomass using LiDAR height and crown area derivatives.  相似文献   

19.
多尺度数字地貌等级分类方法   总被引：4，自引：1，他引：3  
参考已出版的全国各级各类比例尺的地貌类型图的分类方案及图例表达,探讨了中国1：100 万数字地貌的等级分类方法,采用基于形态、成因、物质和年龄等地貌要素,综合反映地貌特征的等级分类指标和分类体系,初步构建了中国多个国家基本比例尺（即1：400 万、1：100 万、1：50 万、1：25 万、1：5 万）数字地貌等级分类方法,发展了由连续分布的多边形图斑反映形态成因类型,以及由离散的点、线和面图斑共同反映形态结构类型的数字地貌类型数据组织方式,构建了多尺度数字地貌类型的编码方法。该研究可为发展多尺度地貌类型图的编制提供方法基础,也可为当前正在进行的地理国情监测工程的大比例尺地貌类型信息普查提供分类规范和技术支持。  相似文献   

20.
新疆农业地貌分类：以编制新疆1：100万农业地貌图为例   总被引：1，自引：0，他引：1  
乔木  陈模 《干旱区地理》1994,17(4):53-61
针对新疆地域辽阔，地形起伏巨大，山地层状地貌显著，盆地封闭、干旱，风成和流水地貌发育等特点，着眼于地貌与农业的关系，采用形态与成因相结合的分类原则，以地貌与农业关系密切的海拔高程、物质组成、相对高差、坡度等要素为指标，制定新疆农业地貌分类系统，划分农业地貌类型。  相似文献   

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