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EncyclopediaofGIS • Shashi Shekar Hui Xiong (Eds.) Encyclopedia of GIS With723Figuresand90Tables 123 SHASHISHEKHAR McKnightDistinguishedUniversityProfessor FacultyofComputerScienceandEngineering UniversityofMinnesota Minneapolis,MN55455 USA HUIXIONG AssistantProfessor ManagementScienceandInformationSystemsDepartment RutgersBusinessSchool NewarkandNewBrunswickRutgers,theStateUniversityofNewJersey Newark,NJ07102 USA LibraryofCongressControlNumber:2007933825 ISBN:978-0-387-35973-1 Thispublicationisavailablealsoas: PrintpublicationunderISBN:978-0-387-30858-6and PrintandelectronicbundleunderISBN:978-0-387-35975-5 ©2008SpringerScience+BuisinessMedia,LLC. Allrightsreserved.Thisworkmaynotbetranslatedorcopiedinwholeorinpartwithoutthewrittenpermissionofthepublisher(Springer Science+Business Media, LLC.,233SpringStreet, New York,NY10013, USA),except forbriefexcerpts inconnection withreviews or scholarly analysis. 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Foreword by Brian Berry ThepublicationofadefinitiveEncyclopediaofGISthatlaysoutmanyofthecomputerscience/mathematicsfoundations ofthefieldisamajorevent,theculminationofahalfcenturyofdevelopment.Iwaspartoftheearlieststirringsinthe mid-1950s.AsmallgroupofgeographygraduatestudentsattheUniversityofWashington,WilliamGarrison’s“space cadets,”begantoassemblewhatbecamethefoundationsofcontemporaryspatialanalysisandtorefocusmathematical cartographywhileworkingwithcivilengineerEdgarHorwoodonhisattemptstousetheprintersofthetimetoproduce grey-shadedmaps.OurattentionwascapturedbySputnik,however,wedidn’tanticipatethattheUS’sresponse,therapid developmentofNASAandsatellitesystems,wouldbethekeytotheequallyrapiddevelopment ofremotesensing,or thatglobalpositioningwouldrewritecartography.AmongtheinnovationsofthetimewereTorstenHägerstrand’sfirst simulation models of space-time diffusion processes and early econometric interest in spatial autocorrelation. Both themesarenowcentraltospatialanalysis. TheGISfocus shiftedwhenGarrison, MarbleandIrelocatedtotheChicagoregion. GarrisonandIhelpedfundcivil engineer Howard Fisher’s first generation computer graphics software, SYMAP I, and Marble and I organized NSF workshops to spread the word and drew together an initial overview of the field in Spatial Analysis. Fisher took his ideas to the Ford Foundation and a subsequent grant to Harvard University, where he established the Laboratory for Computer Graphics. The Lab served as the focus for research in the field well into the 1970s, providing the spark to such innovators as Jack Dangermond, who subsequently established ESRI and created what became the world’s mostwidelyusedcomputergraphicssoftware.Meanwhile,hardwaredevelopmentproceededapace,asdidimagingand positioningcapabilitiescreatedbytheDepartmentofDefenseandNASA,facilitatingtheresultingemergenceofdigital cartography and the establishment of the first large-scale Geographic Information Systems such as the Canada Land Inventory.Therest,astheysay,ishistory–albeitgivenanewdynamicbytheInternetandthecontinuedevolutionof computingcapabilitiesbothonthedesktopandinthesupercomputer. Fiftyyearsafterthesebeginnings,theresultisalargeandcomplexfieldspanningmanydisciplines,continuingtogrow andtoexpandintoanexpandingarrayofapplications.Cartographershaveeschewedtheirpen-and-ink,andrudimentary mapmakingisatthefingertipsofeveryonewithInternetaccess.Roadatlasesarefastgivingwaytosatellitenavigation systems.Congresscontinuestobeconcernedwiththeprivacyissuesraisedbygeographicinformationsystemcapabil- ities, yet police and fire departments can no longer function effectively without GIS and Homeland Security without moderndatabaseanddataminingcapabilities.Fromcityplanningtostorelocation,propertytaxationtohighwaybuild- ing,disasterresponsetoenvironmentalmanagement,therearefewarenasinwhichGISisnotplayingasignificantrole. What is important is the cross-cutting capability that was recognized when the NSF funded the Center for Spatially- IntegratedSocialScience(CSICC)attheUniversityofCalifornia,SantaBarbara,ormyownuniversity’sPh.D.program, ajointventureoftheSchoolofEconomic,PoliticalandPolicySciences,theSchoolofNaturalSciencesandMathemat- ics,andtheSchoolofEngineeringandComputerSciences. I like to tell my colleagues that there are three levels of GIS education: “Driver’s Ed,” “Mr. Goodwrench,” and “Design Team.” Driver’s Ed provides essential skills to the broad base of software users, the Mr. Goodwrenches of theworldlearnhowtoputtogetherandmaintainworkingsoftware-hardware installations,whileDesignTeamscreate new and improved GIS capabilities. Most of the new data handling capabilities reside in the arenas of computer science/mathematics,whileadvancesininferencearecomingfrominnovationsintheabilitytohandlespace-timedynamics whilesimultaneouslyaccountingforserialandspatialdependence. TheEncyclopediaofGISprovidesanessentialreferenceworkforallthreecategoriesofusers.Incontrasttothecurrent textbooksinthefield,whicharekeyedtoDriver’sEd,theEncyclopediaalsoprovidesahandysourcebookfortheMr. GoodwrencheswhiledefiningtheplatformonwhichfutureDesignTeamswillbuildbyfocusing–morethanexisting VIII ForewordbyBrianBerry works–onthecomputerscience/mathematicalfoundationsofthefield.IknowthattheGIScommunitywillvaluethis importantreferenceandguide,andIwillcherishitasamilestone.Itmarkshowfarwehavecome–farbeyondwhat ourgroupofpioneersdreamedmightbepossibleahalfcenturyago.ProfessorsShekharandXiongandtheconsiderable communityofcontributors tothecollectionhaveprovideduswithacomprehensiveandauthoritativetreatmentofthe field,extensivelycross-referencedwithkeycitationsandfurtherreadings.Importantly,itisavailableinbothprintedand XMLonlineeditions,thelatterwithhyperlinkedcitations.TheGISworldwillbeindebtedtothem.NoGISbookshelf should,astheysay,bewithoutit. McKinney,Texas BrianJ.L.Berry August,2007 SchoolofEconomic,PoliticalandPolicySciences TheUniversityofTexas,Dallas Dallas,TX USA Foreword by Michael Goodchild GeographicInformationSystemsdatefromthe1960s,whencomputersweremostlyseenasdevicesformassivecom- putation.Verysignificanttechnicalproblemshadtobesolvedinthoseearlydays:howdidoneconvertthecontentsof apapermaptodigitalform(bybuildinganopticalscannerfromscratch);howdidonestoretheresultonmagnetictape (intheformofalinearsequenceofrecordsrepresentingthegeometryofeachboundarylineassequencesofvertices); andhowdidonecomputetheareasofpatches(usinganelegantalgorithminvolvingtrapezia).Mostoftheearlyresearch wasaboutalgorithms,datastructures,andindexingschemes,and,thus,hadstronglinkstoemergingresearchagendas incomputerscience. Over the years, however, the research agenda of GIS expanded away from computer science. Many of the technical problems of computation were solved, and attention shifted to issues of data quality and uncertainty; the cognitive principles ofuserinterfacedesign; thecostsandbenefitsofGIS;andthesocialimpactsofthetechnology. Academic computerscientistsinterestedinGISwonderediftheirresearchwouldberegardedbytheircolleaguesasperipheral– amarginallyinterestingapplication–threateningtheirchancesofgettingtenure.Repeatedeffortsweremadetohave GIS recognized as an ACM Special Interest Group, without success, though the ACM GIS conferences continue to attractexcellentresearch. Theentriesinthisencyclopediashouldfinallylayanylingeringdoubtstorestaboutthecentralroleofcomputerscience inGIS. Someresearchareas,suchasspatiotemporal databases,have continued togrow inimportance becauseofthe fundamentalproblemsofcomputersciencethattheyaddress,andarethesubjectofseveralrespectedconferenceseries. Geospatialdatamininghasattractedsignificantattentionfromcomputerscientistsaswellasspatialstatisticians,anditis clearthattheacquisition,storage,manipulation,andvisualizationofgeospatialdataarespecial,requiringsubstantially differentapproachesandassumptionsfromthoseinotherdomains. Atthesametime,GIShasgrowntobecomeaverysignificant applicationofcomputing. Sometimearound 1995, the earlier view of GIS as an assistant performing tasks that the user found too difficult, complex, tedious, or expensive todobyhand,wasreplacedbyoneinwhichGISbecamethemeansbywhichhumanscommunicatewhattheyknow aboutthesurfaceofEarth,withwhichtheycollectivelymakedecisionsabout themanagement ofland,andbywhich theyexploretheeffectsofalternativeplans.Ahostofnewissuessuddenlybecameimportant:howtosupportprocesses ofsearch,assessment,andretrievalofgeospatialdata;howtoovercomelackofinteroperabilitybetweensystems;how tomanagelargenetworksoffixedormobilesensorsprovidingflowsofreal-timegeographic data;howtoofferuseful servicesontheverylimitedplatformofacellphone;andhowtoadaptandevolvethetechnologyinordertorespondto emergenciesandtoprovideusefulintelligence.Arevitalizedresearchagendaforcomputerscienceemergedthatshows nosignofdiminishing,andisreflectedinmanyofthetopicsaddressedinthisencyclopedia. Forexample,computerscientistsareengagedinthedevelopmentofdatastructures,algorithms,andindexingschemes tosupportthehugelypopularvirtualglobes(GoogleEarth,Microsoft’sVirtualEarth,NASA’sWorldWinds)thathave emerged in the past few years and are stimulating a whole new generation of applications of geospatial technology. Researchisongoing onsensornetworks, andthecomplexprotocols thatareneededtohandle flowsofreal-timedata frommassivenumbersofdevicesdistributedovertheEarth’ssurface,inareasofscientificinterestsuchastheseafloor, invehiclesacquiringdataontrafficmovement,andinbattlefields.Semanticinteroperability,ortheabilityofsystemsto sharenotonlydatabutthemeaningofdata,remainsathornyproblemthatwillchallengetheresearchcommunityfor manyyearstocome. As a collection of well-written articles on this expanding field, this encyclopedia is a welcomed addition to the GIS bookshelf.ThefactthatitscompilershavechosentoemphasizethelinksbetweenGISandcomputerscienceisespecially welcome.GISisinmanywaysaboundaryobject,touseatermcommoninthecommunityofsciencehistorians:afield X ForewordbyMichaelGoodchild thathasemergedbetweentwoexistingandrecognizedfields,inthiscasecomputerscienceandgeography,andwhich hasslowlyestablisheditsownidentity.Asitdoesso,contributions suchasthiswillhelptokeepthoselinksalive,and toensurethatGIScontinuestoattracttheinterestofleadingresearchersincomputerscience. MichaelF.Goodchild NationalCenterforGeographicInformationandAnalysis andDepartmentofGeography UniversityofCalifornia SantaBarbara,CA USA Preface Interest in Geographic Information Systems, Science, and Services (GIS) has tremendously grown in recent years in many different ways. Researchers from a variety of academic disciplines are using spatial thinking and GIS tools to develop spatially-explicit models. Broad public interest in this subject is being fuelled by popular applications like Googlemaps,personal navigation devices,MapQuest,etc.Web-basedsoftware developers areincreasinglyexploring “mash-ups”integratingdifferentinformationsourcestoweb-basedmaps,suchasGoogleEarthandMSVirtualEarth. Therefore, thereisaneed tobring keyGIS concepts andresults toadiverseaudience ascurrent GIS literature(e.g., textbooks,journals,conference-proceedings,trade-books)largelycaterstoeitherGISspecialistsorend-usersofpopular GISsoftware. TheGISresearchcommunityisenthusiasticallyembracingencyclopedias,i.e.,collectionsofarticlesonnumeroustop- icsinafield,asatooltobringkeyideasfromafieldtoageneralaudience.Thisisnotonlyevidentfromthepreparation of multiple encyclopedias of GIS in the 2007–2008 time-frame, but also from the generous time commitments from GISresearcherscontributingtotheencyclopediaprojectsasauthors,fieldeditorsandreviewers.Theconcurrentdevel- opment of multiple GIS encyclopedias helped us define afocus, given the multi-disciplinary nature of thefield. This encyclopedia focuses on computational aspects of a variety of GIS concepts for a variety of reasons. First, computa- tionaladvancesaremakingGISavailabletoawidevarietyofend-users,softwaredevelopersandresearchers.Second, manygeo-spatial datasetsarelargeandgrowingrapidly duetoadvances incyber-infrastructure, includingsensorand data management technologies. This will make computational issues even more critical in the coming years. Finally, computational technologies are advancing at a rapid pace, making new capabilities possible every few years. While therecentadvances,e.g.,GoogleEarthandMicrosoftVirtualEarth,lookimpressive,wearelikelytoseeevenbigger advancesduetogrowingcomputingpowerintheyearstocome. Despitethefocusoncomputational aspectsofGIS,itwasstillchallengingtonarrowdownthelistofpossiblearticles inorder toexplain the key software, datasets, and processes used by geographers and computational scientists.After all, our goal was to provide a comprehensive and authoritative treatment of GIS, providing easy access to the field. Wereviewedthetopicsincalls-for-papersforconferencesandjournalsalongwiththekeywordsinrelevantbooksand modelcurricula. Wealsoconsultedvarious leadersintheGISarea.Additionally, wetriedtobalancethesetoftopics to reflect the interests of industry, government and academia. For example, topics such as GIS standards as well as examplesofGISsoftwarefromindustryandthepublicdomainwereincludedinthetopiclist.Similarly,weincluded topics like crime mapping, evacuation planning and location-based services. Naturally, the list includes a variety of academictopicsrangingfrom“SpatialCognition”to“StatisticalModeling.” Thenext major challenge was to identify suitable field editors and authors representing the world leaders inselected topicareas.Manyresearchersusuallyfocusonconferenceandjournalpapers.Yet,wewerepleasantlysurprisedbythe generosityoftimeandexpertisereceivedfromsomanyenthusiasticGIScolleaguesforthisencyclopediaproject.Field editorswentbeyondtheircallofdutytoidentifyandinvitepotentialauthors,andreviewcontributionsinordertoensure technical quality while working with Springer project managers tokeep the project on schedule. This is awonderful signoftheenergyandcollegialityofthecomputationalGISresearchcommunity. Springer’sencyclopedia groupprovidedthoughtful guidelinesfortheentries.Typicalentriesare3000wordsandpro- vide balance among definition, scientific fundamentals, application domains, and future trends. Many include short definitionalentriescross-referencedtorelatedregularentriesinordertodiscussspecifictermsandconceptssuchasthe GlobalPositioningSystem,DigitalElevation/TerrainModel,andRemoteSensing.Regularentriesincludekeycitations andalistofrecommended readingregardingtheliterature,and(online)internal hyperlinks todefinitional entriesand XII Preface current standards. This Encyclopedia is also simultaneously available as an XML online reference with hyperlinked citations,cross-references,four-colorart,linkstoWeb-basedmaps,andotherinteractivefeatures. KeyFeaturesataGlance • Immediatepointofentryintothefieldforresearchers • A–Zformatallowseasy,intuitiveaccessfornewcomerstothefield • Manyheadersforeasyskimmingandnavigationoftopics • IncludescoverageofGISstandardsindevelopmentbyISO • Cross-referencedentries • Internationallyrenownededitorialboard,bothscientificallyandgeographicallydiverse • Hundredsofcontributorsensurebalancedcoverage • Interactivefeaturesaddtoconvenience,easeofuseandunderstanding • Peer-reviewedentriesassureresearchersthatinformationisvetted • eReferenceisavailableatspringerlink.com ContentOrganization The encyclopedia is divided into 41 fields, each one an important sub-area within GIS. These fields include: Basic Concepts;BasicStorageandRetrievalStructure;CartographyandVisualization;CommercialGIS;CommercialSpatial Databases;CriticalEvaluationofStandardProposals;DataExchangeandInteroperability;DigitalRoadMap;Emergen- cyEvacuations;EvacuationPlanningandOperations;GeosensorNetworks;GeoSpatialSemanticWeb;GISinBusiness Intelligence,Routing;GISIssuesandApplications;IndoorPositioning;InformationCollectionUsingSensorNetwork; OpenSourceGISSoftware;Photogrammetry;RepresentationofInexactSpatialInformation;RoadNetworkDatabases; SecurityandPrivacyinGeospatial Information Systems;Spatial Analysis;Spatial AspectsofBioinformatics; Spatial AspectsofDistributedComputing; SpatialAspectsofMobileComputing; SpatialAssociationDiscovery;SpatialCo- locationRuleMining;SpatialConstraintDatabases;SpatialDataWarehousingandDecisionSupport;SpatialDatabase Modeling for Applications; Spatial Indexing; Spatial Outlier Detection; Spatial Prediction; Spatial Thinking; Spatial TimeSeries;Spatial Uncertaintyand Imprecision; Spatio-Temporal DataModeling; Spatio-Temporal Databases;Sta- tisticalModelingforSpatialData;TesselationDataModels;andUseofSpatialDataforSimulation. Acknowledgements Many people have played a part in the production of this book and we are extremely grateful to them. In particular, field editors who have made excellent efforts include Vijay Atluri, Sudipto Banerjee, Yvan Bedard, Sanjay Chawla, RobertDenaro,LipingDi,FredericoFonseca,AndrewFrank,OscarFranzese,DimitriosGunopulos,ErikHoel,Kath- leen Hornsby, Yan Huang, Robert Kauffman, Baris Kazar, Sangho Kim, Ravi Kothuri, Phaedon Kyriakidis, Xinrong Li,HenryLiu,Chang-TienLu,NikosMamoulis,HelmutMayer,LiqiuMeng,MohamedMokbel,AndreasNeumann, SilviaNittel,LeonOsborne,Sudhanshu SekharPanda,SrinivasanParthasarathy,PeterRevesz,AshokSamal,Markus Schneider,CyrusShahabi,JayantSharma,YufeiTao,VassilisTsotras,OuriWolfson,ChaoweiYang,PushengZhang, andNaijunZhou. WewouldliketothankthemembersofthespatialdatabaseresearchgroupintheComputerScienceDepartmentatthe University of Minnesota. They contributed in many different ways including providing literature surveys, organizing topics,andreviewingarticles.WewouldalsoliketothanksomeofthestudentsenrolledinCsci8701andCsci8715for contributingarticles. Finally,specialthanksareduetomanypeopleatSpringerfortheirenthusiasm,advice,andsupport. Inparticular, we wouldliketothankSusanLagerstrom-Fife,OonaSchmid,JenniferCarlson,AndreaSchmidt,SimoneTavenrath,Sharon Palleschi,andYanaLambert,whoatdifferenttimeshaveplayedkeyrolesinthedevelopmentofthisbook. August,2007 ShashiShekharandHuiXiong