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Topological relations between directed lines and simple geometries

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Science china(Technological Sciences) 2008年第S1期51卷 91-101页

作者： GAO Yong1,ZHANG Yi1,TIAN Yuan1 & WENG JingNong2 1 institute of remote sensing and geographic information system,peking university,beijing 100871,china 2 Colledge of Software,Beihang university,beijing 100083,china 1. institute of remote sensing and geographic information system Peking University Beijing 100871 China2. Colledge of Software Beihang University Beijing 100083 China

Directed lines are fundamental geometric elements to represent directed linear en-tities. The representations of their topological relations are so different from those of simple lines that they cannot be solved exactly with normal methods. In this paper,a new model based on point-set topology is defined to represent the topo-logical relations between directed lines and simple geometries. Through the inter-sections between the start-points,end-points,and interiors of the directed lines and the interiors,boundaries,and exteriors of the simple geometries,this model identifies 5 cases of topological relations between directed lines and points,39 cases of simple lines,and 26 cases of simple polygons. Another 4 cases of simple lines and one case of simple polygons are distinguished if considering the exteri-ors of the directed lines. All possible cases are furthermore grouped into an exclu-sive and complete set containing 11 named predicts. And the conceptual neigh-borhood graph is set up to illustrate their relationship and similarity. This model can provide a basis for natural language description and spatial query language to present the dynamic semantics of directed lines relative to the background fea-tures.

关键词： topological relation directed line simple geometry intersection model

A common sense geographic knowledge base for GIR

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Science china(Technological Sciences) 2008年第S1期51卷 26-37页

作者： ZHANG Yi,GAO Yong,XUE LuLu,SHEN Si & CHEN KaiChen institute of remote sensing and geographic information system,peking university,beijing 100871,china 1. institute of remote sensing and geographic information system Peking University Beijing 100871 China

As background knowledge of geographic information retrieval (GIR),the gazetteers have their limitations. In this paper we propose to develop and implement a com-mon sense geographic knowledge base (CSGKB) instead of the gazetteers. We define that CSGKB is concerned with the representation of geographic knowledge in human brain and the simulation of geographic reasoning in daily life. Traditional geographic information system (GIS) is based on the model of map with its data based on geographic coordinates and its computation based on geometry. However,CSGKB,which is made up of geographic features and relationships and is based on qualitative spatio-temporal reasoning,can be viewed as the direct model of geographic world. This paper also discusses the characters of CSGKB and pre-sents its structure which is composed of knowledge base,inference engine,geo-graphic ontology and learner. The applications using CSGKB include geographic information retrieval (GIR),natural language processing (NLP),named entity rec-ognition (NER),Semantic Web,etc. At present,our work focuses on the design of geographic ontology and the implementation of the CSGKB knowledge base. In this paper we describe the CSGKB ontology structure,top ontology,geographic loca-tion ontology,spatial relationship ontology,and domain ontologies. Finally,we in-troduce the current state of implementation of CSGKB and give an outlook on our future researches.

关键词： geographic information retrieval common sense geographic knowledge base geographic ontology

Architecture and key technologies of grid geographic information system

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Science china(Technological Sciences) 2008年第S1期51卷 102-113页

作者： FANG Yu,HUANG Zhou,CHEN Bin,WU Lun & YIN DaFei institute of remote sensing and geographic information system,peking university,beijing 100871,china institute of remote sensing and geographic information system Peking University Beijing 100871 China

The highly efficient and stable collaborative computation platform for geospatial information can be constructed on the basis of Grid computing technology,com-bined with Peer-to-Peer (P2P) computing technology and geospatial database technology. This paper proposed the architecture and key technologies of the Grid GIS (geographic information system) incorporated with P2P structure,and corre-spondingly a Grid GIS prototype named Nebula was designed and then imple-mented. Nebula is a suite of middleware for geospatial Grid computing,which could be deployed onto various service nodes in network. Based on Grid protocols and infrastructure,Nebula provides invocation interfaces to users in form of Grid services. By using P2P message based communication mechanism,complex geospatial computation tasks could be accomplished by Nebula in a collaborative way. This paper introduced Nebula's architecture and key modules,and according to experimental data,we discussed the Grid GIS's advantages,application scenar-ios and future directions.

关键词： Grid GIS distributed geospatial computing Peer-to-Peer computing

A distributed spatial computing prototype system in grid environment

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Science china(Technological Sciences) 2010年第S1期53卷 25-32页

作者： WU Lun,YAN MengLong,GAO Yong,YANG ZhenZhen,ZHAO Yong & CHEN Bin institute of remote sensing and geographic information system,peking university,beijing 100871,china 1. institute of remote sensing and geographic information system Peking University Beijing 100871 China

Digital Earth has been a hot topic and research trend since it was proposed,and Digital china has drawn much attention in *** a key technique to implement Digital china,grid is an excellent and promising concept to construct a dynamic,inter-domain and distributed computing *** is appropriate to process geographic information across dispersed computing resources in networks effectively and cooperatively.A distributed spatial computing prototype system is designed and implemented with the Globus *** important aspects are discussed in *** architecture is proposed according to the characteristics of grid firstly,and then the spatial resource query and access interfaces are designed for heterogeneous data *** open-up hierarchical architecture for resource discovery and management is represented to detect spatial and computing resources in grid.A standard spatial job management mechanism is implemented by grid service for convenient *** addition,the control mechanism of spatial datasets access is developed based on *** prototype system utilizes the Globus Toolkit to implement a common distributed spatial computing framework,and it reveals the spatial computing ability of grid to support Digital china.

关键词： distributed geographic information processing grid computing Digital china GIS

Integrative inversion of land surface component temperature

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Science china Earth Sciences 2005年第11期48卷 2011-2019页

作者： FAN Wenjie1 & XU Xiru1,2 1. institute of remote sensing and geographical information system, peking university, beijing 100871, china 2. Center of remote sensing and GIS of beijing Normal university, beijing 100875, china 1. institute of remote sensing and geographical information system Peking University 100871 Beijing China 2. Center of remote sensing and GIS of beijing Normal university 100875 Beijing China

In this paper, the row winter wheat was selected as the example to study the com-ponent temperature inversion method of land surface target in detail. The result showed that the structural pattern of row crop can affect the inversion precision of component temperature evi-dently. Choosing appropriate structural pattern of row crop can improve the inversion precision significantly. The iterative method combining inverse matrix was a stable method that was fit for inversing component temperature of land surface target. The result of simulation and field ex-periment showed that the integrative method could remarkably improve the inversion accuracy of the lighted soil surface temperature and the top layer canopy temperature, and enhance inver-sion stability of components temperature. Just two parameters were sufficient for accurate at-mospheric correction of multi-angle and multi-spectral thermal infrared data: atmospheric trans-mittance and the atmospheric upwelling radiance. If the atmospheric parameters and component temperature can be inversed synchronously, the really and truly accurate atmospheric correction can be achieved. The validation using ATSRII data showed that the method was useful.

关键词： components temperature, inverse pattern, atmospheric correction

A method for blind separation of components information from mixed pixel

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Progress in Natural Science:Materials International 2006年第07期16卷 760-765页

作者： FAN Wenjie and XU Xiru ( institute of remote sensing and geographical information system, peking university, beijing 100871, china Center of remote sensing and GIS of beijing Normal university, beijing 100875, china) [a]institute of remote sensing and geographical information system Peking University Beijing China [b]Center of remote sensing and GIS of beijing Nornal university Beijing China

In the field of remote sensing, it is important to separate the component information from mixed pixel. If the physical process of remote sensing can be expressed by a set of linear equations, the remote sensing information matrix is equal to the weight matrix multiplied by the component information matrix. Generally speaking, the precondition of retrieval of component information matrix is that the weight matrix is known. However, the blind signal separation (BSS) method can separate the matrix unconditionally, whose basic principle is that the additive information needing separation can be achieved from the statistical characteristics contained in a mass of samples in the remotely sensed information matrix. Therefore, the values of the component information matrix and the weight matrix can be estimated. The wave shape of components can be retrieved by BSS, but the amplitude cannot. In this paper, the plant-soil mixed pixels were chosen as the studying targets in this paper to quantitatively separate the component information and solve the uncertainty of BSS. Simulation and field test verify the reliability of the method. Results show that the BSS can be one of the effective methods of mixed pixel separation, and the foreground of application is very promising.

关键词： mixed pixel component information blind signal separation.

L curve for spherical triangle region quadtrees

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Science china(Technological Sciences) 2004年第3期47卷 265-280页

作者： YUAN Wen1,CHENG Chengqi1,MA Ainai1 & GUAN Xiaojing2 1.institute of remote sensing and Geography information system,peking university,beijing 100871,china 2.Centre of State information,beijing 100045,china peking Univ Inst Remote Sensing & Geog Informat Syst Beijing 100871 Peoples R China Ctr State Informat Beijing 100045 Peoples R China

The sequence of facets and nodes has a direct influence on the efficiency of access to spherical triangle region quadtree. Based on the labeling schema by Lee, spatial curves both for facets and nodes are proposed and the main algorithms for coordinate translation, node Lsequence generation and visiting nodes are presented. In particular,constant time algorithms for generating node Lsequence are advanced by using bit manipulation operations,which can be easily implemented with hardware. In L curve the distance between three nodes of a facet is mostly limited in a range of small value, thus making fast access possible. Though codes of sibling facets are continuous, the difference between codes of some cousins may occasionally be very large and makes the distance of a few facets also very large, thus greatly increasing the mean node distance and the total traversing distance. Therefore an m cluster of nodes is proposed as a basic storage unit fo n cluster, which should store eery shared node in each,and the distance between three nodes of a facet is limited to a controllagle scope.

关键词： global grid, spherical triangle region quadtree, SQT, QTM, space-filling curve.

A semantic geographical knowledge wiki system mashed up with Google Maps

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Science china(Technological Sciences) 2010年第S1期53卷 52-60页

作者： GAO Yong,GAO Song,LI RunQiang & LIU Yuinstitute of remote sensing and geographical information systems,peking university,beijing 100871,china 1. institute of remote sensing and geographical information systems Peking University Beijing 100871 China

A wiki system is a typical Web 2.0 application that provides a bi-directional platform for users to collaborate and share much useful information ***,computers cannot well understand the wiki pages in plain *** user-generated geographical content via wiki systems cannot be manipulated properly and efficiently unless the geographical semantics is explicitly *** this paper,a geographical semantic wiki system,Geo-Wiki,is introduced to solve this ***-Wiki is a semantic geographical knowledge-sharing web system based on geographical ontologies so that computers can parse and storage the multi-source geographical ***,Geo-Wiki mashed up with map services enriches the representation and helps users to find spatial distribution patterns,and thus can serve geospatial decision-making by customizing the Google Maps APIs.

关键词： geo-ontology semantic wiki mashup Google Maps

Positioning localities from spatial assertions based on Voronoi neighboring

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Science china(Technological Sciences) 2010年第S1期53卷 143-149页

作者： GONG YongXi 1,2,3,LI GuiCai 1,LIU Yu 2 & YANG Jian 1 1 Shenzhen Key Lab of Recycling Economy,peking university Shenzhen Graduate School,Shenzhen 518055,china 2institute of remote sensing and geographical information systems,peking university,beijing 100871,china 3College of Urban and Environmental Science,peking university,beijing 100871,china peking Univ Shenzhen Grad Sch Shenzhen Key Lab Recycling Econ Shenzhen 518055 Peoples R China peking Univ Inst Remote Sensing & Geog Informat Syst Beijing 100871 Peoples R China peking Univ Coll Urban & Environm Sci Beijing 100871 Peoples R China

With the rapid development of Internet,much spatial information contained in non-structured or semi-structured documents is available on the World Wide *** such documents,localities are always textually described using spatial relationships and named places,instead of numerical ***,extracting positional information from locality descriptions is an important *** this paper,we bridge two aspects of locality descriptions,namely generating locality descriptions and positioning localities,and provide a method to compute probability density according to the selection probability of a reference object to describe the position of the target *** operation on uncertainty field is used to deal with locality description involving multiple reference *** metrics are introduced to measure the results of positioning *** choose the mixed selection probability function based on Euclidean distance and Voronoi stolen-area to compute probability density ***,we use three cases to demonstrate the proposed methods.

关键词： geographic information science positioning locality Voronoi neighboring probability density function