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851.
Chuanrong Zhang Tian Zhao Weidong Li 《International Journal of Applied Earth Observation and Geoinformation》2010
Although the fast development of OGC (Open Geospatial Consortium) WFS (Web Feature Service) technologies has undoubtedly improved the sharing and synchronization of feature-level geospatial information across diverse resources, literature shows that there are still apparent limitations in the current implementation of OGC WFSs. Currently, the implementation of OGC WFSs only emphasizes syntactic data interoperability via standard interfaces and cannot resolve semantic heterogeneity problems in geospatial data sharing. To help emergency responders and disaster managers find new ways of efficiently searching for needed geospatial information at the feature level, this paper aims to propose a framework for automatic search of geospatial features using Geospatial Semantic Web technologies and natural language interfaces. We focus on two major tasks: (1) intelligent geospatial feature retrieval using Geospatial Semantic Web technologies; (2) a natural language interface to a geospatial knowledge base and web feature services over the Semantic Web. Based on the proposed framework we implemented a prototype. Results show that it is practical to directly discover desirable geospatial features from multiple semantically heterogeneous sources using Geospatial Semantic Web technologies and natural language interfaces. 相似文献
852.
Yixiang Tian Markus Gerke George Vosselman Qing Zhu 《ISPRS Journal of Photogrammetry and Remote Sensing》2010,65(4):395-408
The paper presents an automatic method for the reconstruction of building models from video image sequences. These videos may be recorded using a hand-held camera or a camera mounted on a moving car. Such terrestrial video sequences are economic and flexible. Presenting buildings as geometric models–rather than for instance a representation from a simple meshing of 3D points–enables one to perform a wide range of analyses. However, sparse 3D points and 3D edges do not contain topological relations. Therefore, integrating building structure knowledge into the reconstruction steps plays an important role in our method. First, some rules are applied to reasonably group the extracted features. Then, a suitable outline and normal direction are specified for each surface patch. Based on these surface patches, a hybrid model- and data-driven method is used to recover a building model from both the extracted surface patches and hypothesized parts. Using the building structure knowledge leads to a simple and fast reconstruction method, and also enables one to obtain the main structures of buildings. The results show that this method correctly sets up topological relationships between generated surface patches and also obtains reasonable structure models in occluded areas. Therefore, the reconstructed models satisfy requirements for both visualization and analysis. 相似文献
853.
854.
An Adaptive Method of High Accuracy Surface Modeling and Its Application to Simulating Elevation Surfaces 总被引:3,自引:0,他引:3
An adaptive method is employed to speed up computation of high accuracy surface modeling (HASM), for which an error indicator and an error estimator are developed. Root mean‐square error (RMSE) is used as the error estimator that is formulated as a function of gully density and grid cell size. The error indicator is developed on the basis of error surfaces for different spatial resolutions, which are interpolated in terms of the absolute errors calculated at sampled points while paying attention to the landform characteristics. The error surfaces indicate the magnitude and distribution of errors in each step of adaptive refinement and make spatial changes to the errors in the simulation process visualized. The adaptive method of high accuracy surface modeling (HASM‐AM) is applied to simulating elevation surface of the Dong‐Zhi tableland with 27.24 million pixels at a spatial resolution of 10 m × 10 m. Test results show that HASM‐AM has greatly speeded up computation by avoiding unnecessary calculations and saving memory. In addition, HASM‐AM improves simulation accuracy. 相似文献
855.
856.
21世纪我国面临的测绘基准面问题 总被引:4,自引:0,他引:4
大地水准面与深度基准面是测绘垂直基准面的主要因素。文中探讨了我国测绘垂直基准面的现状及其存在的问题 ,提出了改进测绘垂直基准面之拙见 ,以便在下一个世纪提到议事日程与同仁商榷。 相似文献
857.
本文讨论了水稻受重金属镉和铜污染伤害后的光谱反射特性的变化,为遥感监测污染提供基本依据。使用高分辨率光谱辐射计在自然状态下实地测量了受污染的水稻光谱特性,比采集叶片在室内测量更接近于实际情况,便于结合遥感图像进行定性和定量分析研究。 结果表明,镉和铜拌土生长的水稻在分蘖期受到的影响最明显,无论是在生理上还是在反射光谱方面变化都比较显著。因此,对水稻受重金属污染的遥感监测最佳时间为分蘖期,有效波段为0.54—0.58,0.64—0.69,0.74—0.80微米。综合对水稻光谱的各种分析方法,如波形分析,微分光谱,绿度指数和主成分变换等技术,水稻在分蘖期,对高浓度的监测效果较好,而对低浓度效果不甚明显。 相似文献
858.
859.
860.
洞庭湖生态环境日趋恶化,生态事件频发。基于RIA架构的洞庭湖生态事件采集网络GIS能更好地面向公众进行生态事件预警,快速地登记并发布生态事件,对及时掌握生态事件相关信息及精确预警具有重要意义。系统采用RIA、WebService,SuperMap iServer Java 6R,SuperMap iClient for Flex等技术开发,设计了数据存储、服务器、客户端三层逻辑架构,包括基础地理信息发布与浏览、生态事件信息发布、生态事件采集与管理三个顶层模块。系统在洞庭湖国家级自然保护区实际应用后,取得了较好的应用效果。 相似文献