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Liu Y.,Shanghai Surveying and Mapping Institute | Liu Y.,Wuhan University | Lan Q.,Hohai University | Fei L.,Wuhan University
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2012

To establish large-scale multi-level database of land use, we propose a new method to generalize polygon roads to polygon-polyline mixed roads. When integrating road polygon datasets, the network road polygons are divided into three types, retention, deletion and reduced maintenance parts. Deletion parts are removed, and the reduced maintenance parts are changed into linear roads, and the retention parts and the linear roads form the new mixed road dataset of the new target scale. Moreover, the deletion and reduced maintenance road polygons will be divided into small pieces and then incorporate into polygons which matches these pieces in order to ensure the land use data having no gaps. Source

Huang M.,Wuhan University | Huang M.,Fujian Provincial Geomatics Center | Hu P.,Wuhan University | Xia L.,Shanghai Surveying and Mapping Institute
2010 18th International Conference on Geoinformatics, Geoinformatics 2010 | Year: 2010

The management of moving objects is an intensive study area in recent years. Currently many researches focus on objects freely moving on 2-dimensional space, and a lot of index strategies have been proposed, while they are not applicable for objects moving on fixed networks. As objects moving on fixed networks are pervasive in real application, its study is of great practical significance. As changing over time frequently is a main characteristic of moving objects' position, index strategies for moving objects' trajectories need to provide efficient dynamic updating ability besides high query performance. In this paper, we propose an efficient index strategy named Grid Partition R-Tree (GPR-Tree), for indexing trajectories of moving objects on fixed network. By dividing the network space into grids of different size and indexing trajectories in each grid, GPR-Tree provides efficient query as well as updating performance for moving objects' trajectories. Source

He J.,Hubei University | Fei L.,Wuhan University | Huang L.,Wuhan University | Liu Y.,Shanghai Surveying and Mapping Institute
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2013

An indirect generalization method for contour lines is proposed based on the 3D Douglas-Peucker algorithm. Firstly, the source contour lines are taken as the unformatted DEM, i.e., 3D randomly distributed discrete points and are generalized by the 3D Douglas-Peucker algorithm, then the generalized point set can be used as the input of the contour line rendering, finally the rendered contour lines are taken as the result of indirect generalization of contour lines. Preliminary experiments have proved that the contour lines generalized by this method have the geometrical accuracy as well as the topological consistence with the help of major geomorphologic structure lines, and the proposed method has a good adaptability for both input and output contour lines. Therefore, it has a good prospect of application. Source

Cheng L.,Nanjing University | Zhang W.,Shanghai Surveying and Mapping Institute | Zhong L.,Nanjing University | Du P.,Nanjing University | Li M.,Nanjing University
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing | Year: 2015

Three-dimensional (3-D) models require a quality evaluation prior to their use in specific applications, regardless of whether the modeling process is automatic or manual. A comprehensive framework to evaluate visual and geometric quality of 3-D models is proposed in this study for use in various applications. To evaluate the visual quality, we propose a new concept that we call a fuzzy realistic index, which is based on fuzzy set theory and information entropy methods. Geometric accuracy is determined by deconstructing a 3-D model into the elements of point, line, and plane. The campus of Nanjing University, China, is the experimental area for this study, consisting of 106 3-D building models having various styles and complexity. In this experiment of visual quality, we selected 30 models and invited 100 participants in order to illustrate the power of the proposed fuzzy realistic index. Furthermore, with the support of the proposed framework, this study analyzes the influence of building complexity and of the perceptions of different people upon the quality of constructed 3-D models. Results of these experiments reveal the applicability of the proposed framework in evaluating the quality of 3-D models. © 2008-2012 IEEE. Source

Yu S.,East China Normal University | Yu B.,East China Normal University | Song W.,University of Louisville | Wu B.,East China Normal University | And 5 more authors.
Landscape and Urban Planning | Year: 2016

Vegetation provides many environmental benefits to the city, and daily access to vegetation contributes to the well-being and psychological status of urban residents. Understanding and measuring urban dwellers' view-based exposure to greenery has become an important and much needed task for assessing the quality of urban life. This paper presents a new quantitative and objective indicator, the Floor Green View Index (FGVI). It is defined as the area of visible urban vegetation on a particular floor of a city building. The method for estimating FGVI consists of three steps: creating observation points and setting observation platform for each detected floor, conducting viewshed analysis and extracting visible urban green space, and computing the Floor Green View Index. The method is proposed and tested through a case study of the Lujiazui region, Shanghai, China, using airborne Light Detection and Ranging (LiDAR) data and aerial photographs. The new indicator and methods can be used as powerful quantitative tools for urban design, landscape architecture, urban green planning and management. © 2016 Elsevier B.V. Source

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