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利用约束D-TIN进行建筑物多边形凹部结构识别与渐进式化简 总被引:1,自引:0,他引:1
分析了位于建筑物多边形外侧的凹部结构特征及其类型,探讨了一种基于凹部层次结构的建筑物多边形渐进式化简方法,即以三角形为形状基元,用约束Delaunay三角化方法对建筑物多边形进行空间剖分,从凹部三角形树中提取三角形序列,通过匹配特征序列识别凹部的基本模式,以确定和实施相应的凹部化简方法,在此基础上迭代执行识别-化简过程,以实现对建筑物复杂凹部的渐进式化简。实验分析表明,该方法具有结构化和渐进综合的特点。 相似文献
104.
To fully understand forest resources, it is imperative to understand the social context in which the forests exist. A pivotal part of that context is the forest ownership. It is the owners, operating within biophysical and social constraints, who ultimately decide if the land will remain forested, how the resources will be used, and by whom. Forest ownership patterns vary substantially across the United States. These distributions are traditionally represented with tabular statistics that fail to capture the spatial patterns of ownership. Existing spatial products are not sufficient for many strategic-level planning needs because they are not electronically available for large areas (e.g., parcels maps) or do not provide detailed ownership categories (e.g., only depict private versus public ownership). Thiessen polygon, multinomial logit, and classification tree methods were tested for producing a forest ownership spatial dataset across four states with divergent ownership patterns: Alabama, Arizona, Michigan, and Oregon. Over 17,000 sample points with classified forest ownership, collected as part of the USDA Forest Service, Forest Inventory and Analysis (FIA) program, were divided into two datasets, one used as the dependent variable across all of the models and 10 percent of the points were retained for validation across the models. Additional model inputs included a polygon coverage of public lands from the Conservation Biology Institute’s Protected Areas Database (PAD) and data representing human population pressures, road densities, forest characteristics, land cover, and other attributes. The Thiessen polygon approach predicted ownership patterns based on proximity to the sample points in the model dataset and subsequent combining with the PAD ownership data layer. The multinomial logit and classification tree approaches predicted the ownership at the validation points based on the PAD ownership information and data representing human population, road, forest, land cover, and other attributes. The percentage of validation points across the four states correctly predicted ranged from 76.3 to 78.9 among the methods with corresponding weighted kappa values ranging from 0.73 to 0.76. Different methods performed slightly, but statistically significantly, better in different states Overall, the Thiessen polygon method was deemed preferable because: it has a lower bias towards dominant ownership categories; requires fewer inputs; and is simpler to implement. 相似文献
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全球离散格网系统是一种新型的全球多尺度空间数据模型,相关问题的研究已引起学术界的广泛关注并已取得可喜进展。其中,格网量测体系的建立是当前学术界的研究难点,同时也是格网实用化必须解决的核心问题。文中将平面六边形格网上任意覆盖区域抽象为"格点多边形",推导并证明了其面积计算公式,通过对比算例验证了结论的正确性和优越性。 相似文献
107.
dr. agro. LEIF PETERSEN mag.scient. HENRIK BREUNING MADSEN 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):25-35
Petersen, Leif og Madsen, Henrik Breuning: Possible Effects of Ground Water Lowering on Some Peat Soils in Sjælland. Geografisk Tidsskrift 77:25–35 København, June 1, 1978. In four peatlands in the central part of Zealand nine profiles have been investigated to estimate the effect of a lowering of the groundwater level. 相似文献
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Abstract Estimation of direct runoff, peak discharge or hydrographs is often necessary in small to medium-sized ungauged basins. Different models are used in practice for these purposes, depending on the type of problem, the available data and the prevailing runoff mechanisms in the study basin. This paper discusses the applicability of the curve number procedure developed by the US Soil Conservation Service (SCS) to estimate direct runoff in basins characterized by small to gentle undulating slopes mainly covered with natural grasslands. Rainfall and runoff data measured in the Cañada de Los Chanchos basin in Uruguay is used to fit the curve numbers and to analyse the antecedent soil moisture condition proposed by the SCS. 相似文献
109.
M. Delafontaine G. Nolf N. van de Weghe M. Antrop Ph. de Maeyer 《International journal of geographical information science》2013,27(6):719-735
As positional error is a major issue in the assessment of spatial data quality, its propagation has been studied widely in map overlaying. However, few studies deal with a manifest consequence of positional error in map overlaying, namely sliver polygons. Sliver polygons are generally treated as awkward by-products that need to be removed quickly. Nevertheless, as they represent spurious areas, their nature and properties carry useful information, for example, for land use/cover assessment. Therefore, next to sliver removal, there is a need for intelligent detection and eventually further analysis of sliver polygons. This article proposes a general, semi-automated method for the assessment of slivers in vector polygon layers. A case study in Flanders (Belgium) illustrates a possible application in area estimation evaluation of land use allocation classes. 相似文献
110.
Climate types, biome types, and soil orders are commonly used among physical geographers in research and to describe natural environmental characteristics. However, little attempt has been made to quantify the percentage of global land surface that is covered by combinations of climate types, biomes, and soil orders. This research overlays a world map of 31 climate types produced based on the Köppen–Geiger criteria using gridded NCAR/NCEP reanalysis monthly mean surface air temperature and precipitation data from 1981 to 2010 with global maps of eight biomes adapted from World Wildlife Federation and 12 soil orders from United States Natural Resources Conservation Service. Areas covered by each of the 2976 combinations are then calculated. Results suggest that, as expected, a few climate/biome/soil combinations are most common, such as desert climate/desert biome/entisols, tundra climate/tundra biome/gelisols, and desert climate/desert biome/aridisols. The local nature of soil properties causes small enclaves of unexpected combinations of climate, biome, and soils, and the 10 most extensive climate/biome/soil combinations occupy only one-quarter of the global land surface. The strong correspondence between climate and biome types validates the Köppen–Geiger criteria for categorizing climates based on vegetation realms, even today, despite the general paucity of data available when the criteria were established. 相似文献