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  • 2010 Volume 12 Issue 4
    Published: 25 August 2010
      
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  • ARTICLES
    The Exploration of Putting the Application of Remote Sensing "From the Technical Aspect to Scientific Aspect":A Case Study on Putting forward of the Fault-uplift Mineralization Viewpoint of Sandstone-type Uranium in China
    LIU Dechang, YE Fawang, YANG Xu, ZHAO Yingjun, YI Piyuan
    2010, 12(4): 451-457.
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    Through remote sensing research of uranium deposit in Ordos and Tarim basins,the close relationship of its metallogenic environment and fault-block uplift(fault-uplift structure) was found.Based on this discovery,and combined with modern information technology(GIS,3d visualization,computer simulation,etc.) and geophysical and geochemical information such as gravity,aeromagnetic,airborne radiometric survey and earthquake prospecting,then adding in uranium geology professional knowledge,the information transform was made into new cognition,and finally,a viewpoint of fault-uplift mineralization and the theory of fault-block mineralization in Craton basin of China were put forward.To encircle the fault-uplift structure and its brink is the main direction of prospecting in this type of basin.So,the conception of putting the application of remote sensing "from the technical aspect to scientific aspect",which,was advocated by the late academician Chen Shupeng,was explored.This concept designated the direction of deep development and further application of remote sensing technology.The practice shows that it is an important approach to make full use of the advantages of remote sensing technology at first,to discover and put forward problems,then to use comprehensive information and integration technology,to make extension study of the remote sensing discovery and combine with professional knowledge,to make the data and information transform into innovation cognition,and finally to direct the practice and decision-making.
  • ARTICLES
    Main Characteristics and Primary Applications of Polar-orbiting Satellite FY-3A
    DONG Chaohua, YANG Jun, LU Naimeng, YANG Zhongdong, SHI Jinming, ZHANG Peng, LIU Yujie, CAI Bin
    2010, 12(4): 458-465.
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    The Chinese meteorological satellite program,began from 1970's,consists of two series,i.e.,polar-orbiting satellite series and geostationary satellite series,as well as the ground operational segment.In partnership with the China Aerospace Science and Technology Corporation(CASC),the second generation of polar-orbiting meteorological satellite,i.e.,FY-3A,the first of this series was developed,and launched from the Taiyuan Satellite Launch Centre in China on 27 May,2008.The FY-3A in orbit serves as a moving meteorological observing station,and is equipped with both sounding and imaging payload,providing three-dimensional,quantitative,multi-spectrum global remote sensing data under all weather conditions.It has more powerful applications in several fields over the FY-1 satellites.This satellite provides a unique source of environmental observations of the earth's surface,oceans,atmosphere,and near space.The observations are used to derive profiles of atmospheric temperature and moisture,sea surface temperature,cloud parameters,precipitation rate at ground,snow and ice coverage,fogs,aerosol,ozone profile,ozone amount,outgoing longwave radiation,and so on.The data and products are used in numerical weather analysis and prediction,climate change monitoring,oceanographic,hydrologic,agriculture,forestry,forage grass and natural disasters monitoring and services.The applications of the satellite data can greatly improve the meteorological and climate service and thus benefit the society and national economy.Users in the world can get the data and products from National Satellite Meteorological Centre by some ways for further uses.Now the FY-3A is a necessary part of the World Meteorological Organization(WMO) space-based component of the Global Observing System(GOS).It is not just for China use,but also make contribution to the word.This paper briefly introduces the major characteristics of the satellite data and provides some products and application examples in numerical weather prediction,regional weather and climate change,environmental and nature disaster monitoring.
  • ARTICLES
    Support Vector Machine Based Groundwater Level Monitoring Model by Using Remote Sensing Images
    FU Jun'e, SU Qingxun, PAN Shibing, LU Jingxuan
    2010, 12(4): 466-472.
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    Groundwater is not only an essential component of water resources,but also an extremely sensitive factor of the environment in Northwestern inner land basin.The groundwater dynamic could affect the evolvement of oasis,vegetation growth and development.The remote sensing technique,for its large-scale covering and cost-effective feature,may pay an important role in obtaining information of groundwater level in inner land basin where there is a paucity of basic hydrological data for backward developed monitoring systems.Ground surface reflection is significantly related to the depth of groundwater level for the very few precipitations in arid region.This paper aims to develop the groundwater level monitoring model for in arid region based support vector machine(SVM) regression method by using remote sensing.The spatial distribution and changes of ground-water level in time-series can be monitored and analyzed with vegetation and surface temperature information from the image radiation.The inputs of the model are the Normal Differential Vegetation Index(NDVI) and Land Surface Temperature(LST) data extracted from the MODIS images products,as well as the field observations of wells.Various kernel functions including the one-order polynomial,cubic polynomial and RBF function for SVM regression method are tested and simulated to find appropriate one for modeling.The research results in Shule River basin of Hexi corridor,Gansu Province illustrate that the model approach proposed is effective especially for the shallow groundwater level monitoring in arid region.The shallow groundwater levels with depth less than 3 meters fit the one-order polynomial kernel function better,and for greater groundwater depth more than 5 meters,it is even more suitable for selection of RBF kernel function or a cubic polynomial nuclear function method to simulate groundwater level.The research results could provide the basic approaches for the water cycle module and hydrology research,as well as support the sustainable water resources development and management in Northwest regions of China.
  • ARTICLES
    3D Landscape Modeling and Application Based on Erdas and DirectX Platform
    YI Piyuan, ZHAO Yingjun, LIU Dechang, LIU Guanghua
    2010, 12(4): 473-479.
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    3D GIS has become a focus field of GIS study currently,and high-resolution satellite image is an important data resource for the 3D GIS construction.In this paper,based on the high-resolution IKONOS satellite stereo images,using the method to extract the 3D visualization information of the research area,including DEM extraction,orthophoto map making,3D information and texture of the ground building,the progress of the DEM extraction was analyzed and the errors of the DEM were corrected.A technical method that uses the ERDAS IMAGINE and 3ds Max software to carry on hybrid modeling was put forward.By complementing the advantages of two kinds of software,this method can accomplish the modeling work of the ground building better.Finally,based on the VC++6.0 platform,combined with the DirectX SDK,the 3D visualization landscape was firstly constructed from two aspects,including the visualization of terrain and the loading of the ground feature models.In this process,in order to improve the operating speed,the Level of Detail algorithm and Mipmap technology were used to optimize the terrain visualization and the texture of the models.Further more,the diversification of the smog was simulated by constructing particle system and many factors of the environment and production facilities that can influence the movement of the smog were calculated and added.Through these work,the production activities of the special facility can be inferred,so it can provide support for the decision analysis.
  • ARTICLES
    The Earthquake Survey of Geological Hazards and Spatial Analysis in Wenchuan County
    WANG Meng, WANG Jun, JIANG Yu, MA Xiaobo
    2010, 12(4): 480-486.
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    By using multi-source remote sensing data,DEM data and topographic maps,the remote sensing of seismic geologic hazard in Wenchuan County was interpreted and investigated.It has identified characteristics of geological hazards such as location,type,size and boundaries,summarized seismic landslides in ulcer slip type,ulcer collapse type,projectile type,peeling type and shattered remote sensing image features.The relationship between seismic geologic hazard and earthquake fault,valley topography,elevation,slope and lithology was analyzed.In the investigation of geological disasters in the earthquake,the high-resolution satellite images and aerial photo data have advantages such as high-speed and wide range collection,high-degree interpretation,higher timeliness,and so on.The high-resolution satellite images and aerial photo data can be applied in dealing with unexpected geological disasters in an earthquake,in a regional seismic survey of geological hazards.The advantage of multi-source remote sensing data,especially the high-resolution satellite images and the aerial photography,was summed up in the detailed investigation of seismic geologic hazard.
  • ARTICLES
    Geographic Information Sharing Behavior Model and Its Empirical Research
    YU Xu, El-Sayed Ewis Omran, HE Jianbang
    2010, 12(4): 487-495.
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    With the development of informationization and the separation between data management departments and application departments,geographic information sharing becomes one of the most important objectives for the spatial information infrastructure construction,and it is one of the hot topics in the filed of GIS research in recent years.Geographic information sharing is not only a necessary request of the development of earth system science,but also much importance of promoting science data sharing.Summarily,the research on geographic information sharing includes two levels,i.e.technical and non-technical.However,the former has been paid more attention in the past decades.In the light of experience so far suggesting that there are considerable non-technical barrier that are likely to discourage geographic information sharing,it is important to systematically explore and assess what factors are that contribute to such resistance.Geographic information sharing is essentially a social process;it involves also human behavior that is shaped by socio-cultural conditions.Geographic information sharing networks are made up of people and the relationships between those people.Any system relying on people and relationships is subject to the complexity of social coordination and motivation of involved individuals.This paper focuses on the socio-cultural aspects of geographic information sharing.At first,the geographic information sharing behavior model is introduced in this paper.Through questionnaire survey and empirical research in China,the non-technical factors influencing geographic information sharing in China are quantificationally researched.Combining with Omran's empirical research results in Egypt and the Netherlands,influence of motivational factors and cultural differences on geographic information sharing behavior is studied.On the basis of qualitative and quantitive analysis,geographic information sharing behavior model is validated and revised,and some relative suggestions for the construction of geographic information sharing environment in China are made.The results of quantitative analysis also show that the geographic information behavior model is applicable in different cultural backgrounds.Since the research of geographic information sharing behavior is still in its infancy,it should be deeply researched from new perspectives in the future.
  • ARTICLES
    Conceptual Framework and Representation of Geographic Knowledge Map
    XU Jun, PEI Tao, YAO Yonghui
    2010, 12(4): 496-502,509.
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    People have been working for years on geo-information map in different fields of geography since it was proposed.However,most current works on geo-information map stay at the stage of representing geographic phenomena or processes as traditional map does,while lack of knowledge representation and reasoning,so it shows no difference with traditional cartographic map.This results in difficulties in extracting information automatically from geo-information maps,so experts' knowledge and experience are required in order to acquire spatial or temporal patterns through the spatial distribution of geographic phenomena on geo-information maps.This paper proposes the concept of geographic knowledge map,which uses measurements in feature dimensions as coordinate frame instead of geographic coordinate system and displays the characters of objects and the relationships between them with different signals.In this way,geographic knowledge map can disclose spatial-temporal patterns in different feature dimensions which are less possible to be found in real world and geo-coded map.In this paper,the conceptual framework and properties of geographic knowledge map is described,and its characteristics are concluded.Geographic knowledge map is not only graphic representation of geographical knowledge,but also a formal language of knowledge representation.It represents knowledge with structured formal diagrams,has specific semantics and syntax,so it is computable.Through computation of geographic knowledge map,we can transfer the knowledge it represents into other formal language descriptions.It is a way of geographic knowledge visualization,and a method of data mining and knowledge discovery as well.
  • ARTICLES
    An Estimation Method of Dynamic Population within an Urban Local Area
    ZHANG Zimin, ZHOU Ying, LI Qi, LIN Yuxian
    2010, 12(4): 503-509.
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    A problem involved in emergency decision-making and many city management works is to evaluate the population within some given urban areas at a random time.The unknown spatial areas and evaluation time which constitute two fundamental uncertainty features of the problem bring great difficulty for its solution.Following the overall disciplines presented in daily traveling of urban residents,we know that people basically arrange their activities around various city buildings.Another explanation for the phenomenon is residents travel between buildings because they are attracted by the functions of them.So,in this paper,a method is developed to evaluate the static population inside a given area,which uses the data of buildings for habitation and average housing floorage per urban resident according to statistics.While another step must be done for assess the dynamic population,which is to confirm the population attracted by each type of building at any time.Two new indices are introduced: building correction coefficient and building attraction rate.The former refers to the ratio of average accommodated people between other building types and residential building.A rated accommodation people for each type of buildings can be achieved using the index.The latter is the ratio of real accommodation people to rated one.Here we divide the work day or break day all into seven periods according to the general time distribution of residents' traveling activities,and confirm a building type category by reference to one used in the occurrence rate investigation of city transportation.The two indices are estimated using the traveling investigation data of residents and vehicles.Then the dynamic population is drawn based on the proposed method.A case of chemical emergency in Beijing is imagined to demonstrate the application of the method and the issues concerned with parameter fixing that is the key to the method is discussed.
  • ARTICLES
    Assessment of Wind Erosion Hazard Degree in Typical Farming-Pastoral Ecotone of Northern China
    LIANG Haichao, SHI Huading, BAI Zhongke, HU Yunfeng
    2010, 12(4): 510-516.
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    Land degradation and sand storm caused by wind erosion is one of the most serious environmental problems in Farming-Pastoral Ecotone of Northern China,and the determination of wind erosion rate and the evaluation of wind erosion hazard in regional scale are puzzling problems in wind erosion research.The quantitative evaluation of soil wind erosion hazard in Erenhot-Zhangjiakou transect could provide scientific basis for prevention and treatment of wind erosion.Though many factors influence soil wind erosion hazard,among which vegetation cover,average degree of land surface relief,degree of soil dryness and intensity of wind energy were identified as the main factors that control wind erosion.By means of remote sensing inversion and meteorological data,one factor database about the above factors was established with the help of ArcGIS software,and the evaluation model of soil erosion hazard was established by Analytic Hierarchy Process(AHP),then spatial distribution of soil erosion hazard in the study area was obtained.Finally,combined with data of land use in the study area,the background of natural environment and land use was analyzed,upon which comes into view of the spatial pattern of soil erosion hazard.Result shows that area of Severe Hazard in the study area is 1.47×104km2,area of intense hazard is 6.09×104km2,area of Moderate hazard is 3.47×104km2,area of Slight Hazard is 3.45×104km2,area of no hazard is 2.19×104km2.The figure of hazard shows "wind erosion hazard increases gradually from southeast to northwest in the study area",which is consistent with the vegetable and climate condition in the study area.The trend is almost the same with previous researches in this field which indicated this approach of combining GIS and AHP is effective for assessing wind erosion hazard.Moreover,the study area is located at the north path of sand storms and is the sources that strengthen sand storms,so,the result could not only be used for preventing and governing soil wind erosion,but also for taking some measures to control the sand storm.
  • ARTICLES
    Object-oriented Information Extraction of Water Bodies and Glaciers in Extreme High Altitude Area:A Case Study of the Core Area of Mt.Qomolangma (Everest) National Nature Preserve
    ZHANG Jiping| LIU Linshan, ZHANG Yili, NIE Yong| ZHANG Xueru, ZHANG Qinqin
    2010, 12(4): 517-523.
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    Extreme high altitude area is the birthplace of rivers and glaciers.It is quite difficult to accurately extract information of rivers and glaciers from remote sensing images due to the strong undulating topography and arduous field verification.This study chose ASTER image as the data source to extract water body and glacier information in the core area of Mt.Qomolangma(Everest) National Nature Preserve(QNNP) by the method of object-oriented automatic classification.In order to ensure the accuracy of information extraction,the digital elevation model(DEM) and its derived data(slope,aspect),normalized difference vegetation index(NDVI),as well as other indexes that help to distinguish water bodies and glaciers from other land objects,such as Normalized Difference Snow/Ice Index(NDSII) and band math(b1-b3;b3/b4) were stacked respectively as added spectral bands,which contributed to the supplementation of the spectral characteristics of target surface objects.Then,multi-level image segmentations were carried out for each type of water body and glacier to meet their different requirements of segmentation scale.Image segmentation is the key step of object-oriented automatic classification,which requires many times of repeated experiments to find out the most suitable segmentation scale.After the accomplishment of image segmentation,the spectral characteristics,texture features and spatial structure characteristics of each target surface object were comprehensively analyzed.And then,the knowledge-based extraction principles for each type of water body and glacier were established by determining the thresholds of each index according to their histogram features.The classification accuracy was assessed based on field survey results.According to the accuracy assessment,the total accuracy of image classification is 95.14% which satisfies the accuracy requirement of object-oriented automatic classification.This study improved the model for automatic and quick extraction of water bodies and glaciers from ASTER images in extreme high altitude area.
  • ARTICLES
    Spatial Topological Relationships:An Overview and Analysis
    WU Changbin, LV Guonian
    2010, 12(4): 524-531.
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    Topological spatial relationship is the basis of GIS research issue,and is of great importance to spatial data storage and expression,spatial query and analysis and practical application.Spatial cognition and semantics of topological relations,spatial expression of topological relations,topological relations reasoning,and spatio-temporal topological relations are introduced as several aspects of research.Especially,formal expression of spatial topological relations has been a hot topic in GIS,among which RCC(Region Connection Calculus),Intersection Model,2D-String Model and so on are well known.Some recent studies,focusing around the complex object,expression of topological relations between uncertain objects,are mainly discussed.Since current models can hardly represent more complex point,line and region,they must be improved or extended.For uncertainty and ambiguity are some of natural characteristics of geographic objects,it is essential to describe topological relationships between uncertain objects.In addition,some recent research literatures also address the topological relationship between three-dimensional objects,moving objects,etc.Summing up the above,the representation of topological relationships is a complex issue,which related to geographic,GIS,computer graphics and other disciplines of knowledge.Although the studies of topological spatial relations have made progress,there are still some problems.It is to be enhanced in future studies that the more practically topological relation models are applied to solve problems in real works.
  • ARTICLES
    Access and Integration on Geospatial Data and its Distributed Query
    GAO Ang, CHEN Rongguo, ZHAO Yanqing, YAN Xun
    2010, 12(4): 532-540.
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    Integration of distributed spatial data source is critical in geospatial data storage and analysis.In the solution of data grid architecture,data service is introduced to integrate different heterogeneous resource.Access and integration of data service is the key method to build the infrastructure of data sharing and integration.In data grid infrastructure,OGSA-DAI middleware provides uniform access to distributed heterogeneous databases and allows queries to be run over these as if they were a single database.Different from the database connection layer between clients and data,DAI provides server-side data workflow engine designed for data integration,federation and distributed query support across multiple types of database and file system.In this paper,we propose the data grid architecture for geospatial data sharing and integration,which is based on grid service container and data grid middleware.Based on the proposed architecture,we provide the data grid based method for spatial data access and integration via data service with the heterogeneous database communication platform.Besides,we introduce distributed query processing(DQP) system to provide high level data integration solution for service-based grids as well as supporting distributed resources query and accessing.In addition,this paper explores combining distributed object query language and geospatial query functions for spatial data sharing and integration on top of data grid component.Object query tree is also provided to illustrate the analysis and execution of query sentence in accordance with SQL Multimedia specification.SQL/MM Spatial is mainstream international standards for spatial database access and query.By combining the distributed object query and geospatial query,we hope to have leverage with strengths in both of them.The approach of spatial data access and integration,as well as the description,deployment and invoking of data services in distributed environment will contribute a lot for the storage and continuous integration of geological survey and remote sensing data.
  • ARTICLES
    Actively Updating and Application Analysis of Multi-Geospatial Data Assimilation
    AN Xiaoya, SUN Qun, ZHANG Xiaopeng, CHEN Yanli
    2010, 12(4): 541-548.
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    Establishing and updating of geospatial database is an important part of National Spatial Data Infrastructure(NSDI),also an important foundation of Digital Earth building.However,there still exist many problems in integrating and efficiently updating geospatial data at the present time,especially,low efficiency in using multi-source geospatial data,low level in automatization and intelligentization,and lack of practical application with the guidance to complete theoretical system and technical framework.In accordance with this,the paper introduces concepts and methods of data assimilation and actively updating of geospatial database.The purpose is to improve the efficiency of multi-source data utilization and the level of automatization.The character of geospatial data assimilation is to combine a variety of mathematical models and data sources effectively,which eventually makes the new data express the objective entity more accurately.Geospatial data actively updating means the computer can respond to the corresponding geographic events actively and implement the predefined updating operations.The actively updating process is triggered by geographic events under control of the geography event-condition-action rules.This paper discusses the concepts,connotation and key techniques of multi-source geospatial data assimilation and actively updating.Key techniques includes: the acquisition,expression and management of updating rules,the discovery,description and expression of geographic component variation information,the updating of geometrical information and attribute information based on the data assimilation,and the actively updating mechanism driven by GECA rules.This paper also presents the mechanism for geospatial data actively updating which is based on data assimilation and driven by GECA(Geographic event-Condition-Action) rules.Finally,the paper applies the optimum interpolation method which is often used in data assimilation for the conflation of multi-source geography spatial data.Compared with other methods,this method can improve data precision.The actively updating mechanism is used in updating fundamental geo-information data of scale 1:500 000.Practice has proved that the updating mechanism can improve the automating and intelligent level of data updating.
  • ARTICLES
    Three-Dimensional Display Component for Rural Folk-Custom Tourism
    DUAN Fuzhou, MA Pengfei, ZHAO Weji, CAI Wenbo, HU Zhuowei
    2010, 12(4): 549-554.
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    In recent years,the increasingly maturing of technology of computer network,computer graphics,virtual reality and space information gives strong support to the development of tourism in our country.China has a long history and rich culture landscape resources,but with not very well developed tourism.Through the advancement of human civilization,rural folk-custom culture landscape with regional characteristics has been paid more and more attention.The importance of rural folk-custom tourism popularization and propaganda has brought attention and consensus to more and more people in modern society.Tourism publications are of great practical significance in tourism.With the problem that currently there were few systems about rural folk-custom tourism,we can only publish and query the character on tourism in the respective of directions of tourists and tourism resources,but rarely can intuitively publish,inquiry and analyze the interrelationship between the space characteristic information and the spatial information.So the consumers have no imagic and visual realization of the scenic spot,also lack continuous display of the virtual reality space and interactive function.Considering this defect,we superpose the two-dimension electronic map to the digital elevation model to form the basic 3D simulation terrain of the demonstration zone for spatial analysis,integrate fast scheduling of the large-scale data,multiscale level of detail of the landscape information,multimedia,WebGIS and virtual reality technology to develop the adaptive component,adaptive display the tourism landscape,for rural folk-custom tourism,for the interest of tourists,enterprise and the village administrative department.This paper indicates that the three-dimensional display component for rural folk-custom tourism will provide a new tool and verifying methods in tourism and it is extensible,portable and reusable.
  • ARTICLES
    Analysis of 3D Virtual Globe's Applicability in Marine Information and the Prototype System Research
    XIAO Rulin, SU Fenzhen, DU Yunyan, HE Yawen, LIU Wei
    2010, 12(4): 555-561.
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    As the growing of 3D Virtual Globe,it has become a popular geospatial information browser,and has been successfully applied in vast of field.However,its application in marine information still exists lot of problems such as low-level application and lack of supports from basic theory and key technology related with marine field.So in this paper,it mainly analyzes its applicability in marine information and researches in its technical roadmap to its application in marine information and the prototype system.Firstly,it reviews the problem and historical reason that exist in its application in marine,points out the advantages which show great potential for its application,also points out the challenges ahead,to which,much attention need to be paid.Secondly,based on the comprehensive analysis of the applicability,it researches into the front technologies in 3D virtual marine and the prototype realization.By taking advantage of technology of the state-of-art such as grid and semantic web,it initiates a strategy of divide and rule that deal with the front end and back end differently to realize the prototype for Digital Ocean in full use of GIS,virtual reality,grid,and semantic web technology.Finally,under the guidance of such technical strategy,a SOA-based multi-layer prototype system(VRMarine) was realized by taking full use of several key technologies such as multi-source marine environmental data exchanging based on XML,service encapsulation and publishing mechanism of marine environmental information,and virtual organization of marine environmental information service and remote visualization.VRMarine not only can reappear the realistic three dimensional scene of marine environment by integrating multi-source of marine geo-information services,but also can support high dimensional spatiotemporal analysis by dynamically integrating of kinds of functional service.Its success tested the feasibility and efficiency of the strategy proposed in previous and also exposed the deficiency in the semantics utilization which is of great significance to the future development of 3D Virtual Globe and the construction of Digital Ocean and will be researched in future.
  • ARTICLES
    Design and Implementation of a Tile Map Service based on the Middleware
    XU Hu, NIE Yunfeng, SHU Jian
    2010, 12(4): 562-567.
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    With the boom of Google Map,Virtual Earth,OpenStreetMap and other free online map services based on Web 2.0,and because of its simple,user-friendly,data-rich,and smooth access,tile map services based on pre-generated techniques are becoming a de facto standard for the new generation of WebGIS,and have posed great challenges to traditional WebGIS.In order to upgrade the WebGIS legacy systems smoothly,and improve the response speed of traditional WebGIS and user experience,this paper designs and develops a tile map service based on middleware technology.Through systematic analysis of its basic principle and system architecture,this paper gives three optimization strategies which are tile spatial index,tiling strategies and the deployment structure.Finally,we make a performance comparison between tile map service middleware and traditional OGC(Open Geospatial Consortium,OGC) standard WMS service.Experimental test data using the world map zoom level 8,under this zoom level there are 32,768 tiles in total,then randomly generated 21,000 request windows which contains 3×3 tiles,and this randomly generated test data are divided into 20 groups,each contains 100 to 2000 request windows successively.We use two kinds of experiments,the first one is sent WMS request directly to a Local GeoServer which hosts WMS services,and the other one is our tile map service middleware which uses multiple threads and simultaneously sends nine tile map requests to TMS middleware.Our experimental results show that comparing with sending WMS request to WMS server directly,the average response time of tile map service reduced by 46%.And the TMS middleware has a high efficiency when cutting map tiles dynamically because of its meta-tiling strategy.The study shows that the tile map service middleware has important application value both in improving traditional WebGIS performance and in upgrading existing legacy systems.
  • ARTICLES
    Research on Regional Land Information Integration Model
    ZHU Siyuan, HUANG Yingchun
    2010, 12(4): 568-573.
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    This paper describes the design and implementation of Regional Land Information Integration Model(RLI2M).Different Land Information System(LIS) cannot communicate with each other because of its inner workflows and data structure.Authors proposed a Regional Land Information Integration Model(RLI2M) to solve the problems which is caused by numerous rigid land resources management laws and regulations.By separating fundamental geo-spatial data and business data,the model can bring out various business applications on one map.By enlarging the definition of Operating Data Storage(ODS),RLI2M utilized a Land Information Operating Data Storage(L-ODS) to reduce redundant spatial data.Therefore,the developing of LIS would focus on business functions instead of data organization.The OLTP data structure design reduces the system respond time to a reasonable level.In addition,RLI2M integrates different business systems by using the message/return mechanism in UML even though each of them is different in inner workflows and data structure.Compound message contains simple orders,geometry features as well as attribute tables.That means business systems can send complex signals to each other for communications.In that case,RLI2M successfully strengthen central management which can prevent the disadvantages brought by independent business systems.This article also introduces an application based on RLI2M which was implemented in Liuzhou City,Guangxi Zhuang Autonomous Region.
  • ARTICLES
    Fast Extraction of Built-up Land Information from Remote Sensing Imagery
    XU Hanqiu, DU Liping
    2010, 12(4): 574-579.
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    The fast expansion of urban built-up land and accompanied sharp decrease in farm land have made timely monitoring of landuse changes become more important than ever before.The ability to monitor the built-up land dynamics in a cost-effective manner is highly desirable for local communities and decision makers alike.Fortunately,satellite remote sensing technique offers considerable promise to meet this requirement.Although the use of remote sensing technique in the monitoring of land use changes has become more and more popular and satellite imagery has been frequently used to discriminate built-up lands from non-built-up lands for the last few decades,the extraction of built-up land information from remote sensing imagery is still not an easy task due largely to the heterogeneous characteristics of the built-up land.Among many techniques developed for the extraction of built-up land information,the index-based built-up index(IBI) was created based on three existing thematic indices rather than original multispectral bands.The use of the three thematic indices-soil-adjusted vegetation index(SAVI),modified normalized difference water index(MNDWI) and normalized difference built-up index(NDBI)-greatly help the delineation of built-up land features in remote sensing imagery,because these three indices represent three major landuse components,which are vegetation,water and built-up land,respectively.Therefore,the IBI can significantly enhance built-up land information while suppressing background noise.Consequently,the built-up land can be effectively extracted from the IBI image with high accuracy.In order to quicken image processing,this built-up extraction technique has been programmed to form an easy-use module using the ER Mapper scripting language.The module was further integrated in the ER Mapper package by adding a button to the manual bar.This allows users to automatically perform the extraction procedure with high accuracy just in a few minutes.
  • ARTICLES
    Simulation by Remote Sensing and Temporal-spatial Analysis of Forest Ecosystem Net Primary Productivity in Fujian Province,China
    JIANG Hong, WANG Xiaoqin, SUN Weijing
    2010, 12(4): 580-586.
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    Net primary productivity(NPP),defined as the net flux of carbon from atmosphere into green plants per unit time,is a fundamental ecological variable to measure the energy input of biosphere and terrestrial carbon dioxide assimilation,to indicate the condition of land surface area and status of a wide range of ecological processes.In recent decades,model simulation becomes a major technique for NPP estimation over large areas,which can be divided into several categories as statistical model,parameter model and process-based model.As one of the essential process-based simulator models,the boreal ecosystem productivity simulator(BEPS) was adopted to simulate the forest ecosystem NPP in this paper.With support of MODIS images,meteorological data and so on,forest ecosystem NPP for Fujian Province of China in 2004 was simulated by BEPS model and validated by forest carbon sink investigation data.The simulated result shows that,in 2004,annual mean NPP of forest ecosystem is about 578.97g C/m2·a,and the sum NPP reaches 46.18×106t C;the order of woodlands NPP is: bamboo ≈ broad-leaved trees>fir>Chinese red pine,and the average NPP is 788.6gC/m2·a,780.0gC/m2·a,519.8gC/m2·a and 437.3gC/m2·a respectively.The time-serials analysis of monthly NPP demonstrates that the forest NPP declined a lot during the period from June to August,which is the highest NPP under usual conditions.The precipitation decrease from June to August in 2004 is most likely to be one of the major factors for NPP decline,after the statistic analysis of meteorological data with monthly NPP.On the other hand,the positive correlation between annual forest NPP and elevation is outstanding,where the determination coefficient reaches 0.99.This special phenomenon implies,to some extent,that with the increase of elevation,the interference from human activity is lightened and the forest ecosystem NPP is improved and sustained.In other words,diminishing human interference to forest ecosystem is one of the key measures to maintain the robust productivity of forest,further to mitigate global climate warming.Finally,the uncertainty of BEPS simulation was discussed in brief with the data and the simulator itself.
  • ARTICLES
    The Regional Cloud-cover Metadata Extraction Based on MODIS Image
    ZHONG Honglin, SHI Runhe, QU Peiqing, ZHANG Huifang, GAO Wei
    2010, 12(4): 587-592.
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    The cloud had a significant influence to the quality of optical remote sensing images and the retrieval accuracy of land surface parameters.As one of the variable spatial-temporal factors,cloud would limit the application of optical remote sensed images.For the MODIS data with its swaths cover about 2330 km,the current metadata standards can only describe cloud quantity of the whole image,which limited regional studies and the application of MODIS images.Based on studies of current remote sensing metadata standards,we introduced a new metadata item named "regional cloud-cover" in order to describe the images' cloud spatial distribution,and extract the cloud cover information of specific areas from the MODIS level two cloud mask production(MOD35).This algorithm can extract provincial cloud quantity fast and accurately,and users can upload the vector boundary data or use tools provided by the system to draw their study area on the map,in order to specify the region that they study in the remotely sensed images,which would bring convenience to the regional research using MODIS data.In this paper,we realized the algorithm in the Visual C++ environment.First,we overlaid the girded vector boundary onto the raster data which has no projection.Then extract the cloud-cover percentage from sub-image that tripped from the original image.Finally we made a comparison between the results retrieved from the remote sensing images before and after geometric correction.It showed that,the geometric correction can improve the accuracy of the result little,but need to take much more time.We also made a comparison of the cloud cover percentage between the whole image and the regional one(Anhui Province),the result shows that the regional cloud-cover can represent the cloud-cover status of the specify region much more accurately than before.