Shanghai Surveying and Mapping Institute

Shanghai, China

Shanghai Surveying and Mapping Institute

Shanghai, China
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Wu B.,East China Normal University | Yu B.,East China Normal University | Wu Q.,Binghamton University State University of New York | Yao S.,East China Normal University | And 3 more authors.
Remote Sensing | Year: 2017

3D building model reconstruction is of great importance for environmental and urban applications. Airborne light detection and ranging (LiDAR) is a very useful data source for acquiring detailed geometric and topological information of building objects. In this study, we employed a graph-based method based on hierarchical structure analysis of building contours derived from LiDAR data to reconstruct urban building models. The proposed approach first uses a graph theory-based localized contour tree method to represent the topological structure of buildings, then separates the buildings into different parts by analyzing their topological relationships, and finally reconstructs the building model by integrating all the individual models established through the bipartite graph matching process. Our approach provides a more complete topological and geometrical description of building contours than existing approaches. We evaluated the proposed method by applying it to the Lujiazui region in Shanghai, China, a complex and large urban scene with various types of buildings. The results revealed that complex buildings could be reconstructed successfully with a mean modeling error of 0.32 m. Our proposed method offers a promising solution for 3D building model reconstruction from airborne LiDAR point clouds. © 2017, by the authors; licensee MDPI, Basel, Switzerland.

Xu M.,Wuhan University | Xin J.,Shanghai Surveying and Mapping Institute | Su S.,Wuhan University | Su S.,Shanghai Surveying and Mapping Institute | And 2 more authors.
Journal of Transport Geography | Year: 2017

Identifying the geographic units with restricted access to intra-urban parks has become a hot issue in transport studies. Previous literature has examined the social inequalities of park accessibility under the Western context; however, the issue has seldomly investigated against the non-Western background, especially in China. Using a case of Shenzhen (China), this paper examines the accessibility to parks of three quality levels (official standard) under four transport modes (public transit, walking, bicycle, and private car). In particular, the daily travel time from each community (8117) to each park (625) was harvested from the Baidu Map during 18:30–20:30 in July 2016. We further, based on the travel time calculations, develop four baseline indicators (the weighted average, the minimum, the maximum, and the standard deviation travel time) and three tolerance indicators of park accessibility (weighted average travel time within visit tolerance thresholds, standard deviation travel time within visit tolerance thresholds, and number of parks within visit tolerance thresholds) to measure park accessibility for each community. Results show that the seven accessibility indicators generate different estimations and the quantified accessibility varies greatly with park quality levels and transport modes. Communities present greater variations in accessibility to the first quality level and second quality level parks via walking and public transit. In addition, hierarchical regression is utilized to quantify the relationships between park accessibility and sociodemographic characteristics at two geographic levels (community and district). It is found that the associations are subjected to park quality, transport modes, and geographic levels. In particular, we discover significant social inequalities in park accessibility under the mode of public transit, walking, and bicycle. Our study should provide some new insights into accessibility research and advance the understanding of unequal park provision in developing countries. © 2017 Elsevier Ltd

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.

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.

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.

Luan K.,Tongji University | Chen P.,Tongji University | Zhang S.,Tongji University | Tong X.,Tongji University | And 4 more authors.
Proceedings of the 2nd International Workshop on Earth Observation and Remote Sensing Applications, EORSA 2012 | Year: 2012

The conventional airborne photogrammetry is difficult to implement in some areas, such as marine, deserts, grassland and high mountain regions where the installation of ground control point (GCP) is dangerous or impossible. With the availability of integrated GPS and inertial measurement units (IMU), which are also called POS, this situation is improved. Direct Georeferencing (DG) using the approach of direct determination of exterior orientation parameters is now possible. This paper discussed the calculation of the sensor's exterior orientation parameters through DG, geometric correction and accuracy assessment of images captured by Marine Airborne Multi-spectral Scanner (MAMS) system. © 2012 IEEE.

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.

Zhao Q.,East China Normal University | Pepe A.,CNR Institute for Electromagnetic Sensing of the Environment | Gao W.,East China Normal University | Lu Z.,Southern Methodist University | And 4 more authors.
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing | Year: 2015

Reclaimed lands are seriously affected by ground settlement episodes, which are primarily caused by unconsolidated soils, and could result in severe damage to buildings and public infrastructures. In this work, we present a differential synthetic aperture radar (DInSAR) analysis of the ground displacement that impacts the ocean-reclaimed areas of the Nanhui New City of Shanghai (China), based on jointly exploiting persistent scatterers (PS) and small baseline (SB) approaches. The mean line of sight displacement velocity maps and the corresponding interferometric time-series of deformation were initially cross-compared to assess the accuracy of both DInSAR techniques in regions subject to long-lasting land reclamation processes. By exploiting a set of 31 SAR images collected by the ASAR/ENVISAT sensor from February 2007 to May 2010, we found the average difference between PS and SB velocity maps at 1.2 mm/year, with a root mean square difference of 5 mm for single measurements. Despite the increased levels of noise in the interferograms, due to the extremely time-varying electromagnetic and geometrical characteristics of the SAR scenes in correspondence to reclamation platforms, these results suggest that during first stages of reclamation processes both DInSAR methods are able to correctly identify points that preserve high level of accuracy. We have thus predicted the forthcoming time evolution of ground displacement over reclaimed platforms by combining DInSAR measurements and geotechnical-derived models, suggesting that approximately 90% of the settlements occur within about 15 years. © 2008-2012 IEEE.

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.

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