共查询到20条相似文献，搜索用时 46 毫秒
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利用二十面体施奈德等积多面体投影构建了球面多分辨率六边形层次网格;通过边界四元组将六边形单元分解到四元三角形及其子单元中处理;利用改进的四元三角网编码方案建立了网格的数字空间、单元层次编码模型和不同实体在球面上的表达方法.在此基础上,提出了球面Voronoi图的生成算法.实验结果表明该算法与现有算法相比具有更高精度. 相似文献
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球面离散网格模型是管理海量数据的有效途径,如何构建球面网格是这类模型的基础问题.文中利用Snyder等积多面体投影建立了平面与球面的对应关系,设计了球面等积三角形和四边形离散网格的生成算法.结合实验分析了两种网格的最大/最小边长比和单元周长均方差两项指标,结果表明全部网格的指标均收敛,适合用作多分辨率地理空间信息的管理. 相似文献
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一种通用球面等积离散网格生成算法 总被引：5，自引：0，他引：5
球面离散网格模型是管理海量数据的有效途径,如何构建球面网格是这类模型的基础问题.文中利用Snyder等积多面体投影建立了平面与球面的对应关系,设计了球面等积三角形和四边形离散网格的生成算法.结合实验分析了两种网格的最大/最小边长比和单元周长均方差两项指标,结果表明全部网格的指标均收敛,适合用作多分辨率地理空间信息的管理. 相似文献
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基于菱形单元的球面离散格网具有结构简单和方向性一致等优点,使得其适用于全球多尺度空间数据建模与分析.本文提出一种球面菱形离散格网正二十面体剖分法.首先根据地球的主要地理特征确定正二十面体各个顶点在球面上的位置;其次针对南北两极处的极点奇异性,建立了球面经纬度坐标与三维直角坐标之间的转换关系,在此基础上提出球面菱形离散格网层次递归剖分算法,并从菱形格网单元面积、长短轴比两方面对剖分结果进行几何形变分析;最后验证了本文方法的可行性,试验结果表明,该方法可有效地构建基于正二十面体的球面菱形离散格网,其总体几何特性明显优于基于正八面体构建的球面菱形离散格网. 相似文献
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六边形全球离散格网系统是支持多源地球空间信息融合处理的优选解决方案,相关研究已引起学术界广泛关注。相较于完整的全球格网,局部不规则区域格网的应用需求更加广泛,相关生成算法是当前六边形全球离散格网系统研究的重要问题之一。将二十面体相邻三角面组合为菱形逻辑结构,在此基础上,提出一种局部区域多孔径六边形格网系统生成算法。首先,分析格网剖分类型,建立离散整数坐标系,描述多孔径六边形格网单元空间位置;其次,将局部区域分解到球面二十面体的菱形逻辑结构上创建子区域;然后,根据子区域边界设计外接最小菱形遍历算法,剔除与目标区域无关单元;最后,遍历最小菱形,生成多孔径局部格网。对比实验结果表明,提出的算法具有灵活性好、效率高等优点,生成的多孔径六边形格网用于栅格数据组织,可显著减少数据量,具有较好的应用潜力。 相似文献
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利用球面离散格网组织空间数据的关键技术 总被引：1，自引：0，他引：1
球面离散格网系统是一种能够一体化表达空间位置和测量精度的新型空间数据模型.在分析其优点的基础上,提出利用球面六边形格网系统组织多源、异构空间数据的基本思路.对其中涉及的高精度离散格网系统设计、层次格网编码与索引方案、实体表达与数据重组、实体查询与分析算法等关键技术提出了解决方案.通过原型系统验证了其可行性. 相似文献
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随着云计算、航天遥感、地理信息、导航等技术的发展,用于空间信息剖分组织的全球多分辨率离散格网模型得到了长足发展。针对已有研究成果和当前研究现状,选取性能优异的六边形作为基本格网单元,Fuller多面体投影作为投影类型,提出了一种基于正八面体构建新型六边形球面离散格网的方法。全文系统地论述了此新型离散格网的生成算法并给出了相应实验结果,最后与基于Snyder等积多面体投影的格网进行比较,得出其特点和应用前景。 相似文献
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Monitoring drought dynamics in the Aravalli region (India) using different indices based on ground and remote sensing data 总被引：5，自引：0，他引：5
C. Bhuiyan R.P. Singh F.N. Kogan 《International Journal of Applied Earth Observation and Geoinformation》2006,8(4):289-302
The hard-rock hilly Aravalli terrain of Rajasthan province of India suffers with frequent drought due to poor and delayed monsoon, abnormally high summer-temperature and insufficient water resources. In the present study, detailed analysis of meteorological and hydrological data of the Aravalli region has been carried out for the years 1984–2003. Standardised Precipitation Index (SPI) has been used to quantify the precipitation deficit. Standardised Water-Level Index (SWI) has been developed to assess ground-water recharge-deficit. Vegetative drought indices like Vegetation Condition Index (VCI) and Temperature Condition Index (TCI) and Vegetation Health Index (VHI) have been computed using NDVI values obtained from Global Vegetation Index (GVI) and thermal channel data of NOAA AVHRR satellite. Detailed analyses of spatial and temporal drought dynamics during monsoon and non-monsoon seasons have been carried out through drought index maps generated in Geographic Information Systems (GIS) environment. Analysis and interpretation of these maps reveal that negative SPI anomalies not always correspond to drought. In the Aravalli region, aquifer-stress shifts its position time to time, and in certain pockets it is more frequent. In comparison to hydrological stress, vegetative stress in the Aravalli region is found to be slower to begin but quicker to withdraw. 相似文献
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地理数据库的关系模型及其实现 总被引：1，自引：0，他引：1
本文从以图论观点分析地理实体入手,系统阐述了地理数据库关系模型的设计法和过程。作者于1984年4～9月间在微型机上设计建立了关系型地理数据库的实方验系统(RGDB)。该系统采用了本文提出的关系模型,采用了可动态扩库的子库组合结构,这种结构具有灵活性和提高空间利用率的优点。RGDB含有多种功能的数据操作命令,除了具有一般检索功能外,还能进行“开窗”选取和十分“自由”的映象选取。本文对RGDB系统的主要性能和实现途径作了扼要介绍。 相似文献
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随着城市面貌日新月异,地下管网的建设也在持续推进,作为城市的地下“神经网络”,全天24 h保障城市的正常运转和发展。本文以实现城市管网管理系统的高可用、无插件、智能化为目标,采用“地上地下一体”“二三维一体”的设计理念,研究基于WebGL的三维智慧管网系统的关键技术,实现了管线设施管理的信息数字化、空间化与图形化。 相似文献
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SVG是一种基于XML的用来描述二维矢量图形和矢量/栅格混合图形的标记语言,虽然SVG不是为了面向地理空间数据发布而制定的标准,但它的许多特性都能被广泛地应用到WebGIS中,从而实现矢量WebGIS。由于SVG通过简单的文本语句描述矢量图像,所以SVG通常数据量很小,并且SVG支持GZIP压缩,所以基于SVG构建WebGIS能减轻网络传输负载,加快地图显示速度。SVG内置了对JavaScript的支持,且SVG可通过DOM解析映像成内存中的树型结构,所以客户层可通过JavaScript对DOM的操作实现对地图的缩放、漫游、查询、图层控制等交互操作。 相似文献
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本文在讨论DDE技术的基础上，对MapInfo的DDE机制的实现作了探讨和分析。根据技园区域GIS的实际开发工作，介绍了利用DDE技术在MapInfo中成功地集成Foxpro和Autocad. 相似文献
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遥感技术在土地利用动态监测中的应用 总被引：8，自引：0，他引：8
金时华 《测绘与空间地理信息》2006,29(1):98-101
主要论述遥感技术在土地监测中的应用,以某地区土地利用动态遥感监测研究项目的运作过程为例进行阐述。首先介绍了土地利用动态监测的具体内容和技术路线。其次,对数据预处理与信息采集的方法与手段进行了探讨。最后,对作业的内、外业主要过程以及应提交的成果作了介绍。 相似文献
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Automatic 3D extraction of building roofs from remotely sensed data is important for many applications including city modelling. This paper proposes a new method for automatic 3D roof extraction through an effective integration of LIDAR (Light Detection And Ranging) data and multispectral orthoimagery. Using the ground height from a DEM (Digital Elevation Model), the raw LIDAR points are separated into two groups. The first group contains the ground points that are exploited to constitute a ‘ground mask’. The second group contains the non-ground points which are segmented using an innovative image line guided segmentation technique to extract the roof planes. The image lines are extracted from the grey-scale version of the orthoimage and then classified into several classes such as ‘ground’, ‘tree’, ‘roof edge’ and ‘roof ridge’ using the ground mask and colour and texture information from the orthoimagery. During segmentation of the non-ground LIDAR points, the lines from the latter two classes are used as baselines to locate the nearby LIDAR points of the neighbouring planes. For each plane a robust seed region is thereby defined using the nearby non-ground LIDAR points of a baseline and this region is iteratively grown to extract the complete roof plane. Finally, a newly proposed rule-based procedure is applied to remove planes constructed on trees. Experimental results show that the proposed method can successfully remove vegetation and so offers high extraction rates. 相似文献
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遥感和GIS技术应用于伊拉克南部Basrah省土地利用/覆盖变化及城市扩张研究(英文) 总被引：2，自引：0，他引：2
In recent years, land use/cover dynamic change has become a key subject that needs to be dealt with in the study of global
environmental change. In this paper, remote sensing and geographic information systems (GIS) are integrated to monitor, map,
and quantify the land use/cover change in the southern part of Iraq (Basrah Province was taken as a case) by using a 1:250
000 mapping scale. Remote sensing and GIS software were used to classify Landsat TM in 1990 and Landsat ETM+ in 2003 imagery
into five land use and land cover (LULC) classes: vegetation, sand, urban area, unused land, and water bodies. Supervised
classification and normalized difference build-up index (NDBI) were used respectively to retrieve its urban boundary. An accuracy
assessment was performed on the 2003 LULC map to determine the reliability of the map. Finally, GIS software was used to quantify
and illustrate the various LULC conversions that took place over the 13-year span of time. Results showed that the urban area
had increased by the rate of 1.2% per year, with area expansion from 3 299.1 km2 in 1990 to 3 794.9 km2 in 2003. Large vegetation area in the north and southeast were converted into urban construction land. The land use/cover
changes of Basrah Province were mainly caused by rapid development of the urban economy and population immigration from the
countryside. In addition, the former government policy of “returning farmland to transportation and huge expansion in military
camps” was the major driving force for vegetation land change. The paper concludes that remote sensing and GIS can be used
to create LULC maps. It also notes that the maps generated can be used to delineate the changes that take place over time.
Supported by the Al-Basrah University, Iraq, the Geo-information Science and Technology Program (No. IRT 0438)China). 相似文献