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International Journal of Digital Earth 2014年第2期7卷 138-157页

作者： Qiliang Liu Min Deng Jiantao Bi Wentao Yang department of surveying and geo-informatics Central South UniversityChangshaChina department of land surveying and geo-informatics Hong Kong Polytechnic UniversityHong Kong Center for Earth Observation and Digital Earth Chinese Academy of SciencesBeijingChina

The discovery of spatio-temporal clusters in complex spatio-temporal data-sets has been a challenging issue in the domain of spatio-temporal data mining and knowledge *** this paper,a novel spatio-temporal clustering method based on spatio-temporal shared nearest neighbors(STSNN)is proposed to detect spatio-temporal clusters of different sizes,shapes,and densities in spatiotemporal databases with a large amount of *** concepts of windowed distance and shared nearest neighbor are utilized to define a novel spatiotemporal density for a spatio-temporal entity with definite mathematical ***,the density-based clustering strategy is employed to uncover spatio-temporal *** spatio-temporal clustering algorithm developed in this paper is easily implemented and less sensitive to density variation among spatio-temporal *** are undertaken on several simulated datasets to demonstrate the effectiveness and advantage of the STSNN ***,the real-world applications on two seismic databases show that the STSNN algorithm has the ability to uncover foreshocks and aftershocks effectively.

关键词： spatio-temporal clustering shared nearest neighbor windowed distance spatio-temporal density foreshocks and aftershocks data mining Digital Earth geo-spatial science geospatial data integration

Error matching detection and robust estimation adjustment approach for map conflation

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Science China(Technological Sciences) 2008年第S1期51卷 48-61页

作者： TONG XiaoHua & DENG SuSu department of surveying and geo-informatics,Tongji University,Shanghai 200092,China department of surveying and geo-informatics Tongji University Shanghai China

The conflation of geographic datasets is one of the key technologies in the realm of spatial data capture and integration in geographic information system (GIS). Map conflation is a complex process of matching and merging spatial data. Due to various reasons such as errors in original data related to map data discrepancies,a great amount of uncertainties exists during the process and this will result in errors in featuring matching,especially point feature. Thus,it is vital to develop the method to detect the errors in feature matching and further the conflation results will not be affected. In this paper,error matching detection and robust estimation adjustment methods are proposed for map conflation. The characteristics of errors in feature matching are first analyzed,then a new approach for map conflation based on the least-squares adjustment is presented,and a robust estimation adjustment method is further proposed to detect and process matching errors. The results of the map conflation test show that the proposed method not only determines the errors in feature matching,but also obtains the optimal merging results in map conflation.

关键词： map conflation robust estimation error feature matching uncertainty

Feasibility analysis of GNSS-based ionospheric observation on a fast-moving train platform(GIFT)

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Satellite Navigation 2021年第1期2卷 278-295页

作者： Shiwei Yu Zhizhao Liu department of land surveying and geo-informatics The Hong Kong Polytechnic UniversityKowloonHong KongPeople’s Republic of China

The ionospheric effect plays a crucial role in the radio communications. For ionospheric observing and monitoring, the Global Navigation Satellite System (GNSS) has been widely utilized. The ionospheric condition can be characterized by the Total Electron Contents (TEC) and TEC Rate (TECR) calculated from the GNSS measurements. Currently, GNSS-based ionospheric observing and monitoring largely depend on a global fiducial network of GNSS receivers such as the International GNSS Service (IGS) network. We propose a new approach to observe the ionosphere by deploying a GNSS receiver on a Hong Kong Mass Transit Railway (MTR) train. We assessed the TECR derived from the MTR-based GNSS receiver by comparing it with the TECR derived from a static GNSS receiver. The results show that the Root-Mean-Squares (RMS) errors of the TECR derived from the MTR-based GNSS receiver is consistently approxi-mately 23% higher than that derived from the static GNSS receiver. Despite the increased error, the findings suggest that the GNSS observation on a fast-moving platform is a feasible approach to observe the ionosphere over a large region in a rapid and cost-effective way.

关键词： Global navigation satellite system(GNSS) Total electron contents(TEC) TEC rate(TECR) Fast-moving train platform

Optimum choice of parameters and numerical schemes for a regional gravimetric Moho recovery

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geodesy and geodynamics 2019年第6期10卷 417-429页

作者： Samurdhika Rathnayake Robert Tenzer department of land surveying and geo-informatics Hong Kong Polytechnic University

Despite practical limitations of isostatic theories to model the Moho geometry are well-known,gravimetric methods are often used in terrestrial studies of crustal structure in regions with a low seismic data ***,these methods are indispensable in planetary *** gravimetric methods have been *** Airy and Pratt theories are defined based on adopting a local compensation *** Vening Meinesz theory assumes a regional isostatic flexural *** Vening Meinesz regional isostatic model generally describes a respond of the lithosphere to a load more realistically than the Airy model over *** Pratt method,on the other hand,better describes a compensation mechanism of the oceanic *** application of a particular isostatic model also depends on applied numerical procedures,parameters for inversion,input data specifications,and many other *** this study,we address some basic aspects by applying local and regional isostatic models for a Moho *** also conduct a spectral analysis to assess a spectral resolution of gravity data that is optimal for a Moho ***,we inspect the influence of low-degree spherical harmonics of gravity field on a Moho *** results are validated using seismic data at the European *** results confirm a better performance of a regional compensation *** also demonstrate that a different thickness of the oceanic and continental crustal thickness should be taken into account as a priori *** analysis indicates that gravity data used for a Moho inversion should optimally have a spatial resolution between degrees 60 to *** also show that low-degree spherical harmonics do not modify significantly the Moho geometry,particularly over regions with a relatively homogenous structure of deep mantle.

关键词： Crust Gravity Moho inversion Isostasy

geoid Deformation and Elevation Influence Caused by Building Loading

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geo-Spatial Information Science 2009年第2期12卷 154-156页

作者：王解先季善标曹月玲余美义 department of surveying and geo-informatics Tongji University

The paper studies the ground vertical deformation and the geoid undulation caused by loading of neighboring buildings, based on the loading tides theory. The influence on elevation is also considered. The results show that the ground vertical deformation and the geoid undulation both reach millimeter magnitude. Therefore, it is obvious that the building loading significantly affects the precise engineering surveying, and it must be seriously considered in application.

关键词： loading tides building loading ground deformation geoid undulation

通过空间结构及网络稳健性理解协同发展--以京津冀地区为例

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Journal of geographical Sciences 2024年第5期34卷 1007-1036页

作者：王浩张校源张晓宇刘若文宁晓刚 Chinese Academy of surveying and Mapping Beijing 100036China School of Information Engineering China University of GeosciencesBeijing 100083China College of land Science and Technology China Agricultural UniversityBeijing 100193China

In the context of accelerated globalization,intercity factor flows are becoming in-creasingly dependent on a reasonable and orderly spatial ***,an indepth study of the optimization and adjustment of spatial structure is essential for coordinated *** study quantitatively evaluated urban development levels and introduced network analysis methods to analyse the spatial structure and robustness of *** results indicated the following:(1)The urban development level in the Beijing-Tianjin-Hebei(BTH)region increased in all dimensions,and the transmission efficiency significantly improved.(2)The spatial structure of the BTH region has been relatively stable,as illustrated by the main pattern of the spatial distribution of central cities,with a trend towards contiguous development.(3)The ranking of network robustness is environment>society>economy,and the core network and key nodes are primarily located within the radiation of the three central cities of Beijing,Tianjin,and Shijiazhuang.(4)The coordinated development of the BTH region is effective but still needs to be optimized and adjusted,and the strategic significance of edge cities has not been completely *** study aims to provide an emerging ana-lytical perspective for optimizing regional spatial structure and promoting regional coordinated development.

关键词： urban network spatial structure network robustness coordinated development Beijing-Tianjin-Hebei(BTH)region

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

High resolution aerosol optical thickness retrieval over the Pearl River Delta region with improved aerosol modelling

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Science China Earth Sciences 2009年第10期52卷 1641-1649页

作者： WONG ManSing NICHOL Janet LEE Kwon Ho department of land surveying and geo-informatics The Hong Kong Polytechnic University Earth System Science Interdisciplinary Center University of Maryland (UMD)

Aerosol retrieval algorithms for the MODerate Resolution Imaging Spectroradiometer (MODIS) have been developed to estimate aerosol and microphysical properties of the atmosphere, which help to address aerosol climatic issues at global scale. However, higher spatial resolution aerosol products for urban areas have not been well researched mainly due to the difficulty of differentiating aerosols from bright surfaces in urban areas. Here, a new aerosol retrieval algorithm using the MODIS 500 m resolution images is described, to retrieve aerosol properties over Hong Kong and the Pearl River Delta region. The rationale of our technique is to first estimate the aerosol reflectance by decomposing the top-of-atmosphere reflectance from surface reflectance and Rayleigh path reflectance. For the determination of surface reflectance, a modified Minimum Reflectance Technique (MRT) is used, and MRT images are computed for different seasons. A strong correlation is shown between the surface reflectance of MRT images and MODIS land surface reflectance products (MOD09), with a value of 0.9. For conversion of aerosol reflectance to Aerosol Optical Thickness (AOT), comprehensive Look Up Tables (LUT) are constructed, in which aerosol properties and sun-viewing geometry in the radiative transfer calculations are taken into account. Four aerosol types, namely mixed urban, polluted urban, dust, and heavy pollution, were derived using cluster analysis on three years of AERONET measurements in Hong Kong. Their aerosol properties were input for LUT calculation. The resulting 500 m AOT images are highly correlated (r = 0.89) with AERONET sunphotometer observations in Hong Kong. This study demonstrates the applicability of aerosol retrieval at fine resolution scale in urban areas, which can assist the study of aerosol loading distribution and the impact of localized and transient pollution on urban air quality. In addition, the MODIS 500 m AOT images can be used to study cross-boundary aeroso

关键词： aerosol retrieval aerosol optical thickness AERONET MODIS satellite image

Detection and analysis of landslide geomorphology based on UAV vertical photogrammetry

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Journal of Mountain Science 2024年第4期21卷 1190-1214页

作者： BI Rui GAN Shu YUAN Xiping LI Kun LI Raobo LUO Weidong CHEN Cheng GAO Sha HU Lin ZHU Zhifu School of land and Resources Engineering Kunming University of Science and TechnologyKunming 650093China Plication Engineering Research Center of Spatial Information surveying and Mapping Technology in Plateau and Mountainous Areas Set by Universities in Yunnan Province Kunming 650093China West Yunnan University of Applied Sciences Key Laboratory of Mountain Real Scene Point Cloud Data Processing and Application for Universities in Yunnan ProvinceDali 671006China

High-resolution landslide images are required for detailed geomorphological analysis in complex topographic environment with steep and vertical landslide *** study proposed a vertical route planning method for unmanned aerial vehicles(UAVs),which could achieve rapid image collection based on strictly calculated route *** effectiveness of this method was verified using a DJI Mavic 2 Pro,obtaining high-resolution landslide images within the Dongchuan debris flow gully,in the Xiaojiang River Basin,Dongchuan District,Yunnan,China.A three-dimensional(3D)model was constructed by the structure-from-motion and multi-view stereo(SfM-MVS).Micro-geomorphic features were analyzed through visual interpretation,geographic information system(GIS),spatial analysis,and mathematical statistics *** results demonstrated that the proposed method could obtain comprehensive vertical information on landslides while improving measurement *** 3D model was constructed using the vertically oriented flight route to achieve centimeter-level accuracy(horizontal accuracy better than 6 cm,elevation accuracy better than 3 cm,and relative accuracy better than 3.5 cm).The UAV technology could further help understand the micro internal spatial and structural characteristics of landslides,facilitating intuitive acquisition of surface *** slope of landslide clusters ranged from 36°to 72°,with the majority of the slope facing east and *** elevation levels were relatively consistent while middle to lower elevation levels gradually decreased from left to right with significant variations in lower elevation *** the rainy season,surface runoff was abundant,and steep topography exacerbated changes in surface *** route method is suitable for unmanned aerial vehicle(UAV)landslide surveys in complex mountainous *** geomorphological analysis methods used will provide references for identifying and describing topographic

关键词： UAV landslide Vertical route SfM-MVS Topographic features

Are topological relations dependent on the shape of spatial objects?

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Progress in Natural Science:Materials International 2005年第11期15卷 1021-1025页

作者： LIU Kimfung Advanced Research Centre for Spatial Information Technology department of land surveying and geo-informatics China The Hong Kong Polytechnic University

Topology is normally considered as independent of shape of spatial objects. This may not necessarily be true in describing relations between spatial objects in GIS. In this paper, we present proof that the topological relations between spatial objects are dependent on the shape of spatial objects. That is, that the topological relations of non-convex sets cannot be deformed to the topological relations of convex sets. The significant theoretical value of this paper is on its findings that topology of spatial objects is shape dependent. This indicates that when we want to describe topological relations between spatial objects in GIS, both topology and the shape of objects need to be considered. As a result, spatial data modeling, query and analysis based on the existing understanding of topology of spatial objects may need re-assessed.

关键词： topological relations homeomorphic map convex set interior boundary components.