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Global characteristics of the second-order ionospheric delay error using inversion of electron density profiles from COSMIC occultation data

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Science China(Physics,Mechanics & Astronomy) 2014年第2期57卷 365-374页

作者： WANG Hu WANG Cheng WANG JieXian DANG YaMing BAI GuiXia WANG QianXin Chinese Academy of surveying and Mapping department of surveying and Geo-informatics TongJi University department of Electrical and Computer Engineering Miami University

It is a well known fact that ionospheric delay error is a predominant factor which influences the positioning accuarcy of *** the main part of the first-order ionospheric delay error can be removed by the frequency-dependent behaviors of the ionosphere,the second-order ionospheric delay error must be eliminated to achieve millimetre-scale positioning *** to COSMIC occultation providing electron density profiles on the global scale,the paper presents the first-order and the second-order ionospheric delay error analysis on the global scale using the inversion of electron density profiles from COSMIC occultation data during 2009–***,because of the special geographical location of three ISR(incoherent scatter radar),the first-order and the second-order ionospheric delay errors are calculated and discussed;the paper also shows and analyzes the diurnal,seasonal,semi-annual variation of ionospheric delay error with respect to signal *** show that for the L1 signal path,the first-order ionospheric delay error is the largest near the equator,which is circa 7 m;the maximum second-order ionospheric delay error are circa 0.6 cm,0.8 cm and 0.6 cm respectively for L1 signals coming from the zenith,the north and the south at 10 degree elevation *** second-order ionospheric delay error on the L1 signal path from zenith are the symmetry between 15°and 15°with respect to magnetic equator,and are nearly zero at the magnetic *** the first time,the second-order ionospheric delay error on the global scale is presented,so this research will greatly contribute to analysing the higher-order ionospheric delay error characteristics on the global scale.

关键词： ionosphere GPS COSMIC ISR IGRF

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Global precision analysis of carrier phase relative positioning in BeiDou navigation satellite system and United States global positioning system

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Science China Earth Sciences 2019年第4期62卷 733-749页

作者： Letao ZHOU Dingfa HUANG Wei FENG Wu CHEN Xi ZHANG Li YAN department of surveying and Geo-Informatics Faculty of Geosciences and Environmental EngineeringSouthWest JiaoTong University department of Land surveying and Geo-Informatics Hong Kong Polytechnic University

In this paper, we derived a high-efficiency formula for calculating the precision of carrier phase relative positioning,analyzed the various factors that affect the positioning accuracy using the carrier phase, and proposed the concept of using a frequency dilution of precision to describe the quantitative effect of different frequency combinations on the positioning precision. To this end, we computed and plotted the global spatial distribution map of the relative positioning dilution of precision for single-day solution, half-hour solution, and single-epoch solution of the global positioning system(GPS), regional Beidou navigation satellite system(BDS2), future global Beidou navigation satellite system(BDS3), and their fusion *** processing software with autonomous intellectual property rights(GCN and VENUS/ARSNet), we solved the measurement data and examined the positioning precision of the single-day solution and single-epoch solution of GPS and *** analysis demonstrated that the B1/B2 frequency positioning precision of BDS2 was better than that of L1/L2 frequency positioning of GPS, but the positioning precision of the BDS2 is worse than that of GPS over most of the service region of the BDS2. Further, the positioning precision of BDS3 is better than that of GPS in the Asia-Pacific region, while it is the opposite in other regions. Based on these conclusions, we put forth some optimization recommendations regarding the signal frequency of the navigation system and GPS measurement standards to serve as references for optimizing the system performance and formulating standards.

关键词： BeiDou navigation satellite system Relative positioning Dilution of precision Frequency dilution of precision Spatial-temporal availability

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A general method of spatio-temporal clustering analysis

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Science China(Information Sciences) 2013年第10期56卷 158-171页

作者： DENG Min LIU QiLiang WANG JiaQiu SHI Yan department of surveying and Geo-informatics Central South University

Spatio-temporal clustering has been a hot topic in the feld of spatio-temporal data mining and knowledge *** can be employed to uncover and interpret developmental trends of geographic phenomenon in the real ***,existing spatio-temporal clustering methods seldom consider both spatiotemporal autocorrelations and heterogeneities among spatio-temporal entities,and the coupling in space and time has not been well *** this paper,a unifed framework for the clustering analysis of spatio-temporal data is proposed,and a novel spatio-temporal clustering algorithm is developed by means of a spatio-temporal statistics methodology and intelligence computation *** method is applied successfully to fnding spatio-temporal cluster in China’s annual temperature database for the period 1951 1992.

关键词： spatio-temporal clustering spatio-temporal autocorrelation spatio-temporal heterogeneity spatio-temporal data mining

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Assessment of GNSS zenith tropospheric delay responses to atmospheric variables derived from ERA5 data over Nigeria

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Satellite Navigation 2023年第1期4卷 167-182,I0005页

作者： Ifechukwu Ugochukwu Nzelibe Herbert Tata Timothy Oluwadare Idowu department of surveying and Geoinformatics Federal University of Technology AkureAkureNigeria

Tropospheric delay is a major error caused by atmospheric refraction in Global Navigation Satellite System(GNSS)*** study evaluates the potential of the European Centre for Medium-range Weather Forecast(ECMWF)Reanalysis 5(ERA5)atmospheric variables in estimating the Zenith Tropospheric Delay(ZTD).Linear regression models(LRM)are applied to estimate ZTD with the ERA5 atmospheric *** ZTD are also estimated using standard ZTD models based on ERA5 and Global Pressure and Temperature 3(GPT3)atmospheric *** ZTD estimates are evaluated using the data collected from the permanent GNSS continuously operating reference stations in the Nigerian *** results reveal that the Zenith Hydrostatic Delay(ZHD)from the LRM and the Saastamoinien model using ERA5 surface pressure are of identical accuracy,having a Root Mean Square(RMS)error of 2.3 mm while the GPT3-ZHD has an RMS of 3.4 *** the Zenith Wet Delay(ZWD)component,the best estimates are derived using ERA5 Precipitable Water Vapour(PWV).These include the ZWD derived by the LRM having an average RMS of 20.9 mm and Bevis equation having RMS of 21.1 mm and 21.0 mm for global and local weighted mean temperatures,*** evaluation of GPT3-ZWD estimates gives RMS of 45.8 *** study has provided a valuable insight into the application of ERA5 data for ZTD *** line with the fndings of the study,the ERA5 atmospheric variables are recommended for improving the accuracy in ZTD estimation,required for GNSS positioning.

关键词： ECMWF reanalysis 5(ERA5) Global navigation satellite systems(GNSS) Global pressure and temperature 3(GPT3) Modelling Nigeria Zenith tropospheric delay(ZTD)

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A novel vehicle navigation map matching algorithm based on fuzzy logic and its application

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Journal of Central South University of Technology 2005年第2期12卷 214-219页

作者：童小华吴颂春吴淑琴刘大杰 department of surveying and Geoinformatics Tongji University Shanghai 200092 China

A new real-time map matching algorithm based on fuzzy logic is proposed. 3 main factors affecting the reliability of map matching, including the distance between the vehicle location and the matching road segment, the angle between the vehicle direction and the road segment direction and the road connectivity are discussed. Fuzzy rules for the distance, angle and connectivity are presented to calculate the matching reliability. 2 indicators for estimating the matching reliability are then derived, one is the lower limit of the reliability, and the other is the limit error of the difference between the maximal value and the second-maximal value of the reliability. A real-time map-matching system based on fuzzy logic is therefore developed. Using the real data of global positioning system(GIS) based navigation and geographic information system(GPS) based road map, the method is verified and the (results) prove the effectiveness of the proposed method.

关键词： map matching fuzzy logic reliability GPS GIS road network

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Bundle adjustment for data processing of theodolite industrial surveying system

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中国有色金属学会会刊：英文版 2001年第2期11卷 307-310页

作者：邹峥嵘丁晓利曾卓乔何凭宗 department of surveying Engineering Central South UniversityDepartment of Land Surveying and Geo-Informatics Hong Kong Polytechnic UniversityHunghom Hong Kong department of Land surveying and Geo-Informatics Hong Kong Polytechnic UniversityHunghom Hong Kong department of surveying Engineering Central South University

The photogrammetric bundle adjustment was used in data processing of electronic theodolite industrial surveying system by converting angular observations into virtual photo coordinates. The developed algorithm has ability of precision estimation and data snooping, do not need initial values of exterior orientation elements and object point coordinates. The form of control condition for the system is quite flexible. Neither centering nor leveling is the theodolite needed and the lay out of theodolite position is flexible when the system is used for precise survey. Experiments carried out in test field verify the validity of the data processing method. [

关键词： electronic theodolite industrial surveying system bundle adjustment

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Dynamic model for landsliding monitoring under rigid body assumption

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中国有色金属学会会刊：英文版 2001年第2期11卷 301-306页

作者：朱建军丁晓利陈永奇 department of surveying Engineering Central South University department of Land surveying and Geo-Informatics Hong Kong Polytechnic University Kowloon Hong Kong

Based on the assumption that the slope bodies are rigid, the dynamic model of the landsiding (forward model) was put forward. According to the dynamic model, the system equations of Kalman filter were constituted. The mechanical status of a slope was hence combined with the monitoring data by Kalman filter. The model uncertainties or model errors could also be considered through some fictitious observation equations. Different from existed methods, the presented method can make use for not only the statistic information contained in the data but also the information provided by the mechanical and geological aspect of slopes. At last a numerical example was given out to show the feasibility of the method. [

关键词： dynamic model Kalman filter rigid body landslide monitoring

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Probability density function and estimation for error of digitized map coordinates in GIS

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Journal of Central South University of Technology 2004年第1期11卷 69-74页

作者：童小华刘大杰 department of surveying and Geo-informatics Tongji University Shanghai 200092 China

Traditionally, it is widely accepted that measurement error usually obeys the normal distribution. However, in this paper a new idea is proposed that the error in digitized data which is a major derived data source in GIS does not obey the normal distribution but the p-norm distribution with a determinate parameter. Assuming that the error is random and has the same statistical properties, the probability density function of the normal distribution, Laplace distribution and p-norm distribution are derived based on the arithmetic mean axiom, median axiom and p-median axiom, which means that the normal distribution is only one of these distributions but not the least one. Based on this ideal distribution fitness tests such as Skewness and Kurtosis coefficient test, Pearson chi-square chi(2) test and Kolmogorov test for digitized data are conducted. The results show that the error in map digitization obeys the p-norm distribution whose parameter is close to 1.60. A least p-norm estimation and the least square estimation of digitized data are further analyzed, showing that the least p-norm adjustment is better than the least square adjustment for digitized data processing in GIS.

关键词： probability density function distribution fitness test least p-norm estimation

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Multiresolution Terrian Model in GIS

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测绘学报 2002年第z1期31卷 92-98页

作者： ZHANG Jin 1,TONG Xiao hua 2 (1. department of surveying and Mapping, Taiyuan University of Technology, Taiyuan 030024,China 2. department of surveying and Geo informatics, Tongji University, Shanghai 200092,China) department of surveying and Mapping Taiyuan University of Technology Taiyuan 030024 department of surveying and Geo-informatics Tongji University 上海 200092

DEM, which becomes a major component of geographic information processing in earth and engineering sciences, has been studied in the GIS literature for a long time. We use DEM to represent the terrain in GIS. The more data are available, the better representations of a terrain can be built. But not all tasks in the framework of a given application necessarily require the same accuracy, and even a single task may need different levels of accuracy in different areas of the domain. Multiresolution models, such as LOD, offer the possibility of representing and analyzing a terrain at a range of different levels of detail. In this paper, some key issues in multiresolution DEM model are studied. Three main models are focused on Hierarchical TIN(HTIN), multiresolution terrain model based Delaunay and Hierarchical Dynamic Simplification. The advantages and disadvantages of these methods are analyzed. The technology of tile to tile edge match is studied to maintain the consistency between adjacent edges and tile edges in HTIN model. And the Hypergraph based Objected oriented Model(HOOM) is presented to divide and code spatial area and describe the terrain feature in adding and deleting points based on Delaunay rule retriangulating. The conclusions have been drawn in the end.

关键词： DEM multiresolution LOD GIS

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Low-cost cloud computing solution for geo-information processing

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Journal of Central South University 2016年第12期23卷 3217-3224页

作者：高培超刘钊谢美慧田琨 department of Land surveying and Geo-Informatics Hong Kong Polytechnic University Institute of Geomatics Department of Civil EngineeringTsinghua University

Cloud computing has emerged as a leading computing paradigm,with an increasing number of geographic information(geo-information) processing tasks now running on *** this reason,geographic information system/remote sensing(GIS/RS) researchers rent more public clouds or establish more private ***,a large proportion of these clouds are found to be underutilized,since users do not deal with big data every *** low usage of cloud resources violates the original intention of cloud computing,which is to save resources by improving *** this work,a low-cost cloud computing solution was proposed for geo-information processing,especially for temporary processing *** proposed solution adopted a hosted architecture and can be realized based on ordinary computers in a common GIS/RS *** usefulness and effectiveness of the proposed solution was demonstrated by using big data simplification as a case *** to commercial public clouds and dedicated private clouds,the proposed solution is more low-cost and resource-saving,and is more suitable for GIS/RS applications.

关键词： cloud computing geo-information processing geo-processing

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