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Chen Y.,Central South University | Yi Z.,Central South University | Yi Z.,Key Laboratory for Urban Geomatics of National Administration of Surveying | Kuang C.,Central South University | Dai W.,Central South University
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2016

Ambiguity resolution is one of the key technologies for high precision GPS positioning. Accelerating ambiguity fixing can expand the application and improve the reliability of GPS positioning. Based on the characteristics of single-frequency GPS kinematic positioning, a new method to accelerate ambiguity fixing is proposed in this paper. First, a receiver and epoch double differenced approach was used to get the epoch-differenced coordinate information between neighbouring epochs. Then, the epoch-differenced coordinate information is combined with the ambiguity normal equation. Adding epoch-differenced coordinate information to the ambiguity normal equation can decrease the ill-posed-ness of the normal equation, so the accuracy of the floating ambiguity solution was improved and the convergence time of ambiguity was shortened. Experimental results show that the new method can accelerate ambiguity resolution in GPS relative kinematic positioning with good application value. © 2016, Research and Development Office of Wuhan University. All right reserved.


Zhu L.,Beijing University of Civil Engineering and Architecture | Zhu L.,Key Laboratory for Urban Geomatics of National Administration of Surveying | Shortridge A.M.,Michigan State University | Lusch D.,Michigan State University
Journal of Applied Remote Sensing | Year: 2012

Light detection and ranging (LiDAR) point cloud data can contain millions of point returns from a diverse range of surface features, and directly reconstructing buildings from these data is challenging. Trees and other vegetation pose a particular problem in many built environments. This paper investigates several efficient procedures for detecting buildings and excluding vegetation using LiDAR and imagery data. Two general approaches for identifying and filtering out returns from vegetation are investigated: the first uses a normalized difference vegetation index (NDVI) image, while the second uses height differences. The utility of an entropy filter for improving NDVI filter performance as well as two distinct approaches for height-difference modeling are also evaluated. All methods use efficient raster-based algorithms for filtering while retaining the high spatial precision of the vector LiDAR point returns. Following removal of nonbuilding points, remaining points are segmented into distinct building features. In addition, we place particular emphasis on the analysis of processing challenges and special cases as well as the accuracy of these different methods on a large-volume LiDAR dataset covering a challenging build environment. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE).


Xu M.,Beijing University of Civil Engineering and Architecture | Xu M.,Key Laboratory for Urban Geomatics of National Administration of Surveying | Wei S.,Beijing University of Civil Engineering and Architecture | Wei S.,Key Laboratory for Urban Geomatics of National Administration of Surveying | And 2 more authors.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2016

The demand for indoor navigation is increasingly urgent in many applications such as safe management of underground spaces or location services in complex indoor environment, e.g. shopping centres, airports, museums, underground parking lot and hospitals. Indoor navigation is still a challenging research field, as currently applied indoor navigation algorithms commonly ignore important environmental and human factors and therefore do not provide precise navigation. Flexible and detailed networks representing the connectivity of spaces and considering indoor objects such as furniture are very important to a precise navigation. In this paper we concentrate on indoor navigation considering obstacles represented as polygons. We introduce a specific space subdivision based on a simplified floor plan to build the indoor navigation network. The experiments demonstrate that we are able to navigate around the obstacles using the proposed network. Considering to well-known path-finding approaches based on Medial Axis Transform (MAT) or Visibility Graph (VG), the approach in this paper provides a quick subdivision of space and routes, which are compatible with the results of VG.


Zhang X.,Beijing University of Civil Engineering and Architecture | Zhang X.,Key Laboratory for Urban Geomatics of National Administration of Surveying | Kang S.,Beijing BSH e learing Co. | Hou M.,Beijing University of Civil Engineering and Architecture | Liu X.,Beijing University of Civil Engineering and Architecture
International Journal of Emerging Technologies in Learning | Year: 2015

With the rapid development of network technology, large enterprises have established their own online learning and examination systems, respectively. However, those network examination systems are dispersive, closed and disconnected, so resources cannot be utilized in a balanced way, which may cause substantial waste of enterprise resources. To solve such a problem, emerging cloud computing technology with service on demand characteristics and dynamic expansion capability provides the possibility of a shared network examination system, known as a cloud exam support service, with lower costs. A feasible solution for the application of the cloud computing technology in the network examination that combines the theoretical analysis, system design and technical implementation is put forward in this paper. The design, development, and pilot application of the cloud examination system described in this paper show that this study is highly practical, operable, and worthy of application and popularization.


Hwang J.,Sungkyunkwan University | Yun H.,Sungkyunkwan University | Jeong T.,Sungkyunkwan University | Suh Y.,Pukyong National University | And 2 more authors.
Remote Sensing | Year: 2013

This paper focuses on the use of the Land-based Mobile Mapping System (LMMS) for the unscheduled updates of a National Base Map, which has nationwide coverage and was made using aerial photogrammetry. The objectives of this research are to improve the weak points of LMMS surveying for its application to the updates of a National Base Map (NBM), which has rigorous accuracy and quality standards. For this, methods were suggested for the (1) improvement of the accuracy of the Global Positioning System/Inertial Navigation System (GPS/INS) in the long-term exposure of environments with poor GPS reception; (2) elimination of mutual deviations between LMMS data obtained in duplicate to meet resolution standards; (3) devising an effective way of mapping objects using LMMS data; and (4) analysis of updatable regions and map layers via LMMS. To verify the suggested methods, experiments and analyses were conducted using two LMMS devices in four target areas for unscheduled updates of the National Base Map. © 2013 by the authors.


Huang J.,Hubei University | Huang J.,Key Laboratory for Urban Geomatics of National Administration of Surveying | Xing C.,Hubei University | Xing C.,Key Laboratory of Precise Engineering and Industry Surveying
Electronics, Communications and Networks IV - Proceedings of the 4th International Conference on Electronics, Communications and Networks, CECNet2014 | Year: 2015

The problem of crack detection in buildings can be realized by using infrared thermal imaging technology, which is based on the non-contact detection of temperature observation. In this paper, image processing methods of infrared images are described. In addition, a simulation experiment on a building which locates in Wuhan is held to examine the reliability of the methods, and the results show that the theory and methods in this paper have practical significances and can be used for detecting cracks of buildings. © 2015 Taylor & Francis Group, London.


Zhu L.,Beijing University of Civil Engineering and Architecture | Zhu L.,Key Laboratory for Urban Geomatics of National Administration of Surveying | Cai J.,Beijing University of Civil Engineering and Architecture
Accuracy 2014 - Proceedings of the 11th International Symposium on Spatial Accuracy Assessment in Natural Resources and Environmental Sciences | Year: 2014

The aim of the study is the investigation and analysis of the factors affecting the measurements resolution with pulsed time-of-flight (TOF) terrestrial laser scanners. A good understanding of the sources and the relationships between them is necessary to know what size of detail we can get. We subdivide these factors into two groups: internal and external. Based on our studies and the results obtained by other researchers, we have compiled a resolution model for TLS, which is used to estimate the true planer resolution of the point cloud with consideration of the main factors.


Jing C.,Beijing University of Civil Engineering and Architecture | Jing C.,Key Laboratory for Urban Geomatics of National Administration of Surveying | Du M.,Beijing University of Civil Engineering and Architecture | Du M.,Key Laboratory for Urban Geomatics of National Administration of Surveying
Accuracy 2014 - Proceedings of the 11th International Symposium on Spatial Accuracy Assessment in Natural Resources and Environmental Sciences | Year: 2014

Rainfall data is useful in many fieldssuch as urban management, agriculture, and so on. Spatial interpolation is widely used to interpolation continue rainfall data from discrete rainfall gauges. The uncertainty in spatial interpolationis change indifferent region.Paperfocuson urban small areaof Beijing city, Xicheng District and analysesuncertaintyof spatial interpolationfrom four aspects: rainfall gauge number, density, position, spatial interpolation methods.RMSE and cross-validation is adopted to evaluate the accuracy of interpolation and the lowest RMSE is taken as optimal.The results suggest that more gauges can get a good performance with low error compared to little stations; and dense gauges networkgets high accuracy than sparse station. Ordinary kriging is simple than other method and has a good estimation (except co-kriging) in small area spatial interpolation. Co-kriging has a high accuracy in interpolation but complex in computation and must be considering in the other variables.


Liu X.,Beijing University of Civil Engineering and Architecture | Liu X.,Key Laboratory for Urban Geomatics of National Administration of Surveying | Tong X.,Tongji University | Ma J.,Beijing Institute of Geo engineering and Exploration
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2015

In order to satisfy the requirement of identification and tracking the elliptical artificial targets fast and accurately for the image sequences from videogrammetric measurement for structural health monitoring, this paper proposes a systemic algorithm to identify and track the elliptical targets using the image block technique. The proposed method extracts the image block from original images to reduce the amount of data processing for the oval targets tracking. The mathematical morphology and elliptical geometric characteristics are integrated to eliminate the non-elliptical edge information to extract the elliptical contour in the range of image block. At last, the sub-pixel center location for elliptical artificial targets is acquired by the least square algorithm. The experimental results show that RMS error of 0.025 pixel can be achieved by the proposed method, furthermore, compared with the random Hough transform and template recognition algorithm, the tracking efficiency is improved over 5 times. ©, 2015, SinoMaps Press. All right reserved.


Liu J.,Beijing University of Civil Engineering | Liu J.,Key Laboratory for Urban Geomatics of National Administration of Surveying | Zhang J.,CAS Institute of Software | Xu F.,CAS Institute of Software | And 2 more authors.
IEEE Transactions on Geoscience and Remote Sensing | Year: 2014

The contours of polygons generated by the image segmentation technique show jagged outlines and a large number of redundant points. Therefore, the original segmentation contours hardly conform to geographic information system (GIS) data-producing standards without generalization. With the complexity of high spatial resolution remote sensing imagery data, with variable sizes of geographic features and their different distributive patterns, it is hard to build a global contour optimization parameter model to guide parameter settings in large regions effectively. Furthermore, it is also difficult to automatically give a unique set of parameters per object simultaneously. In order to meet the actual requirements of GIS data production, we present an adaptively improved algorithm based on the Douglas-Peucker (DP) algorithm, named AIDP, that integrates the criteria of vertical and radial distance restriction, and design a corresponding parameter-adaptive acquisition method. The proposed AIDP method is evaluated by comparing it with the most widely used DP algorithm implemented in the ArcGIS through visual inspection, quantitative measurements, and applications to water body contours. The experimental results show that AIDP can not only acquire generalization parameters automatically but also greatly speed up the data processing workflow with acceptable results. © 1980-2012 IEEE.

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