地理信息系统GIS.ppt

Geographic Information System-地理信息系统-,主讲：史良胜 副教授武汉大学水利水电学院,课程内容及学时分配,教材及参考资料,1.Geospatial Analysis:A comprehensive Guide to Principles,Techniques and Software Tools,Third Edition(Smith et al.,2009).The online-version can be accessed via http:/.中文版：地理空间分析-原理、技术与软件工具，电子工业出版社2.GIS A Computing Perspective(Michael Worboys,Matt Duckham,2004)3.Geographic Information Analysis(David OSullivan,David J.Unwin,2009)4.ArcGIS实验教程（汤国安，杨昕编著，科学出版社）,考核办法,课堂表现：20%作业情况：20%期末考试：60%,Geographic Information System GIS,Introduction,What is GISIn the beginning.there were mapsRaster and vectorGIS=software+data.The significance of scaleBasic functions of GIS,Geographic Information System GIS,What is GIS？,intuitive description,A map with a database behind it.A virtual representation of the real world and its infrastructure.,Geographic Information System GIS,System:A group of elements organized in such a way that every element is to some degree interdependent(directly or indirectly)with every other element.ex)Ecosystem,Transportation System,Manufacturing System,Geographic Information System GIS,What is GIS?,Information:-.Data vs.Information-.Data:acquisition through direct observation or survey-.Information:the data become information when interpreted in some meaningful way,Geographic Information System GIS,What is GIS?,Information System:Database System,Data Processing System-.Designed to input data,store it,manage it,process it,and output it in the form of meaningful information Geographic Information System:A computer-based information system that enables capture,storage,retrieval,sharing,manipulation,analysis,modeling,and presentation of geographically referenced data.,Geographic Information System GIS,What is GIS?,Geographic Information System GIS,“A computer system for collecting,checking,integrating and analyzing information related to the surface of the earth.”(Rhind,1988),In other words,GIS is both a database system with specific capabilities for spatially referenced data as well as a set of operations for working with the data.It may also be considered as a higher order map.,Geographic Information System GIS,What is GIS?,Set of tools for collecting,storing,retrieving at will,transforming and displaying spatial data from the real world for a particular set of purposes(Burrough,1986),a computer based system that provides four sets of capabilities to handle geo-referenced data:data input data management(data storage and retrieval)manipulation and analysis data output.(Arnoff,1989),Geographic Information System GIS,What is GIS?,Geographic Information System GIS,What is GIS?,a computer based system,spatially referenced data,input,manage,analysis,output,share,Advantages of GIS,GIS is good athandling spatial datavisualisation of spatial dataintegrating spatial dataframework for:analysis and modellingdecision support,Geographic Information System GIS,(dis)Advantages of GIS,GIS is not so good athandling temporal datavisualisation of temporal dataintegrating spatial and temporal dataframework for:analysis and modelling of time dependent datavolumetric analysisuncertainty,Geographic Information System GIS,Geographic Information System GIS,Introduction,What is GIS?In the beginning.there were mapsRaster and vectorGIS=software+data.The significance of scaleBasic functions of GIS,Geographic Information System GIS,Without map?,The story of GIS begins in the world of maps.,The natural environment is extremely complexhighly variable(space and time)complicated further by human action,Geographic Information System GIS,2.1 Map types,Geographic Information System GIS,A Topographic map shows the physical surface features,for example,roads,rivers,buildings.,A Contour map shows lines which connect point locations at which a certain property has the same value,for example,height above sea level,isobars showing air pressure.,A Choropleth map shows areas characterised by some general common feature,for example,political maps,agricultural crop types.,2.2 Map features,all map features can be divided into one of four different categories:,Geographic Information System GIS,?,Point(for example,a cross symbol to represent achurch).Line(for example,a yellow line to represent a road).Polygon shape or area(for example,a blue area torepresent a lake).Text(for example,the name of a building).,2.2 Map features,Geographic Information System GIS,How is map information translated into digital form and read by a computer?The GIS must be able to store information about:The geometry:the shape and location of the objects.The attributes:the descriptive information known about the objects,normally displayed on a map through symbology and annotation.,2.3 Map information,Geographic Information System GIS,Spatial Component Location Information Where is it?All of the data in a GIS are georeferenced.Attribute Component Descriptive Information(characteristics)What is it?,Geographic Information System GIS,Geographic Data:,Spatial+Attribute.,Geographic Information System GIS,Geographic Data:,Geographic Information System GIS,Introduction,What is GIS?In the beginning.there were mapsRaster and vectorGIS=software+data.The significance of scaleBasic functions of GIS,Geographic Information System GIS,3.1 Maps in bits,Computers store information in sequences of binary digits(bits),which form a code for every possible number or letter.,Geographic Information System GIS,This fits with the way maps reference geographical locations on the earths surface,through a system of coordinates.,All locations and shapes can be defined in terms of x and y coordinates from a given grid system:it is these numerical values which are used to translate map information into digital form.,Geographic Information System GIS,3.2 Vector data,There are two fundamental methods of storing map information in digital form,raster and vector.,In vector data the features are recorded one by one,with shape being defined by the numerical values of the pairs of xy coordinates.A point is defined by a single pair of coordinate values.A line is defined by a sequence of coordinate pairs defining the points through which the line is drawn.An area is defined in a similar way,only with the first and last points joined to make a complete enclosure.,Geographic Information System GIS,In vector data the position and shape of the building is captured as a series of four pairs of numerical coordinates.,Geographic Information System GIS,3.3 Raster data,In raster data the entire area of the map is subdivided into a grid of tiny cells.A value is stored in each of these cells to represent the nature of whatever is present at the corresponding location on the ground.Raster data can be thought of as a matrix of values.,Geographic Information System GIS,The values recorded in the cells are either white,blue or red.To reproduce the image the computer reads each of these cell values one by one and applies them to the pixels on the screen.,Geographical Information System GIS,3.4 Vector v Raster,Vector:Relatively low data volumeFaster displayCan also store attributesLess pleasing to the eye,Raster:Relatively high data volumeSlower displayHas no attribute informationMore pleasing to the eye,Geographical Information System GIS,Geographical Information System GIS,In this example the raster data looks nicer but,as you zoom in,the pixel structure becomesobvious.Eventually the image looks like a piece of modern art rather than a detail of a map!The definition of the features is dependent upon the size of the individual grid cells theresolution.The vector data is more like a graph with a line drawn between points,the width staying thesame however close you zoom.,Geographical Information System GIS,Geographical Information System GIS,Geographical Information System GIS,Geographical Information System GIS,Geographical Information System GIS,Introduction,What is GIS?In the beginning.there were mapsRaster and vectorGIS=software+data.The significance of scaleBasic functions of GIS,Geographical Information System GIS,Any successful example of GIS is based on two fundamental components:the map data;and the computer software to perform calculations and analysis.,Geographical Information System GIS,There are many different organisations producing data for use in GIS;,There is also a large industry in GIS software with hundreds of companies producing thousands of products.,Software:GIS Software ArcGIS(ArcInfo,ArcView),MapInfo,etc.Database MS Access,Oracle,Sybase,dBASE Spatial Data Analysis S-PLUS,SPSS Internet Mapping System-ArcIMS System Analysis Tool CASE,Visio,ModelBuilder,Geographical Information System GIS,Geographical Information System GIS,People:IT Administrators GIS Analysts GIS Technicians Application Experts Spatial Data Analyst End Users,Geographical Information System GIS,Hardware:Computer(PC or UNIX)Digitizer/Scanner Plotter/Printer Network System/GPS Units CD-ROM or Data Storage Devices,Geographical Information System GIS,Geographical Information System GIS,Introduction,What is GIS?In the beginning.there were mapsRaster and vectorGIS=software+data.The significance of scaleBasic functions of GIS,Geographical Information System GIS,5.1 Scale basics,A description of scale can lose its meaning the scale of the image on screen can depend on the monitor size.The image above may appear 13 mm long on some screens but not others.,Geographical Information System GIS,5.2 Scale of capture,All GIS packages enable you to zoom in and out on the map data as much as you like.However,all topographic data has a scale of capture,that is,the source data was captured at a particular scale,whether this was a paper map or an aerial photo.,Geographical Information System GIS,It is important to understand the source scale of your data for two fundamental reasons:data from a particular scale should only be viewed within a certain range of magnification for it to make sense visually;and combining two or more datasets together is only appropriate if they have an equivalent scale of capture.,5.2 Scale of capture,Geographical Information System GIS,5.3 Generalisation,The mapping that most of us recognise has been deliberately simplified.,Geographical Information System GIS,5.3 Generalisation,The mapping that most of us recognise has been deliberately simplified.,Geographical Information System GIS,5.3 Generalisation,The mapping that most of us recognise has been deliberately simplified.,Geographical Information System GIS,Geographical Information System GIS,5.3 Generalisation,The mapping that most of us recognise has been deliberately simplified.,Geographical Information System GIS,Geographical Information System GIS,5.3 Generalisation,The mapping that most of us recognise has been deliberately simplified.,large-scale data when viewed at a small scale(zoomed out),appears cluttered whereas small-scale data when viewed at a large scale(zoomed in),appears very sparse.,A cartographer creates these simple,readable maps by selecting information from a larger-scale source.Not all the detail from the source map can be shown.,Geographical Information System GIS,5.3 Generalisation,Sometimes it may be necessary to alter a features true survey position slightly to makespace for the map symbols.Furthermore,the thick red lines of an A road are shown much wider on the map than the actual road is on the ground.This science of small-scale map production is known as generalisation.,Geographical Information System GIS,5.3 Generalisation,Geographical Information System GIS,5.4 Be careful with scale,Many GIS data products are created from generalised map sources,The effects of generalisation will show up if this data is viewed against other more large-scale mapping.,Geographical Information System GIS,5.4 Be careful with scale,The generalised data is not wrong,it is just being magnified more than was ever intended.,When you zoom in,the deviation of the simplified features from their survey position is apparent when the large-scale data becomes visible.,Geographical Information System GIS,Introduction,What is GIS?In the beginning.there were mapsIntroducing raster and vectorGIS=software+data.a formula for successThe significance of scaleBasic functions of GIS,Geographical Information System GIS,Basic functions of GIS?,Geographical Information System GIS,Some examples of GIS in Action:,Land Use Planning,Geographical Information System GIS,Some examples of GIS in Action:,Monitoring of deforestation,Source:UC Berkeley GIS Center,Geographical Information System GIS,Some examples of GIS in Action:,Find the least cost bike route(in terms of traffic and slope)from and to two user defined points,Geographical Information System GIS,Some examples of GIS in Action:,3 D Visualization and Terrain Analysis for transportation planning,Watershed delineation using digital elevation models,Geographical Information System GIS,Some examples of GIS in Action:,Source:Geonmonics,Inc.http:/,Geographical Information System GIS,Some examples of GIS in Action:,Site and demographic analysis for retail/office location,Data Input(Data Model,Data Measurement)Data storage,retrieval and database management Data analysis(manipulation,transformation exploration and confirmation)Output(display and product generation),Geographical Information System GIS,Basic Functions of GIS,Data capture/input:Input data by digitizing,scanning,or direct coordinate entryEdit data in the GIS to correct errors or add featuresLabel the spatial features so they can be identified(names or codes),Geographical Information System GIS,Basic Functions of GIS,Management:Link attribute data to spatial objectsLink to external databasesMake changes in existing databasesUpdate database featuresImport and export from/to other GIS or DBMSCombine map sheets to create large databasesmatch the edges of neighboring map sheets,Geographical Information System GIS,Basic Functions of GIS,Manipulation:Make maps from different sources compatible so that they can be drawn on top of each otherTransformation of coordinates Projection change,Geographical Information System GIS,Basic Functions of GIS,Analysis:QuerySelect features by their attributes:“find all districts with literacy rates 60%”Select features by geographic relationships:“find all family planning clinics within this district”Combined attributes/geographic queries:“find all villages within 10km of a health facility that have high child mortality”,Geographical Information System GIS,Basic Functions of GIS,Analysis(cont.):Buffer:find all settlements that are more than 10km from a health clinicPoint-in-polygon operations:identify for all villages into which vegetation zone they fallPolygon overlay:combine administrative records with health district dataGeocoding/address matching:match an address list with a street mapNetwork operations:find the shortest route from village to hospital,Geographical Information System GIS,Basic Functions of GIS,Modeling:identify or predict a process that has created or will create a certain spatial pa