Geographic Information System.docx

Geographic Information System.docx

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GeographicInformationSystem

GeographicInformationSystem

1.WhatisaGIS?

Ageographicinformationsystem（GIS）isacomputer-basedtoolformappingandanalyzingphenomenathatexistandhappenonthesurfaceoftheEarth. itiscapableofintegrating,storing,editing,analyzing,anddisplayinggeographically-referencedinformation（spatialdataandassociatedattributes）.

GIStechnologyintegratescommondatabaseoperationssuchasqueryandstatisticalanalysiswithuniquevisualizationofferedbymaps. TheseabilitiesdistinguishGISfromotherinformationsystemsandmakeitvaluabletoawiderangeofpublicorganizationsforexplainingevents,predictingoutcomes,andplanningstrategies. 

Mapmakingandgeographicanalysisarenotnew,butaGISperformsthesetasksbetterandfasterthanconventionalmanualmethods. BeforeGIStechnology,onlyafewpeoplehadtheskillsnecessarytousegeographicinformationtohelpwithdecisionmakingandproblemsolving.

2.Historyofdevelopment

35,000yearsago,onthewallsofcavesnearLascaux,France,Cro-Magnonhuntersdrewpicturesoftheanimalstheyhunted.Associatedwiththeanimaldrawingsaretracklinesandtalliesthoughttodepictmigrationroutes.Theseearlyrecordsfollowedthetwo-elementstructureofmoderngeographicinformationsystems:

agraphicfilelinkedtoanattributedatabase.

Inthe18thcentury,modernsurveyingtechniquesfortopographicmappingwereimplemented,alongwithearlyversionsofthematicmapping,e.g.,forscientificorcensusdata.

AnotableexampleofthisisJohnSnow’s1854mapdepictingacholeraoutbreakinLondon,whichprovidedanalysistonarrowthesourceofthecholeratoacontaminatedpump,stemmingtheoutbreak.ImagesofJohnSnow’smaps（Fig.1）.

Fig.1JohnSnow’scholera-map

From

Theearly20thcenturysawthedevelopmentofphotolithographywheremapswereseparatedintolayers.Computerhardwaredevelopmentspurredbynuclearweaponresearchwouldleadtogeneralpurposecomputermappingapplicationsbytheearly1960s.

Theyear1967sawthedevelopmentoftheworld’sfirsttrueoperationalGISinOttawa,OntariobythefederalDepartmentofEnergy,MinesandResources.DevelopedbyRogerTomlinson,itwascalledCanadianGIS（CGIS）andwasusedtostore,analyseandmanipulatedatacollectedfortheCanadaLandInventory（CLI）,aninitiativetodeterminethelandcapabilityforruralCanadabymappinginformationaboutsoils,agriculture,recreation,wildlife,waterfowl,forestry,andlanduseatascaleof1:

250,000.Aratingclassificationfactorwasalsoaddedtopermitanalysis.

CGISwastheworld’sfirstsystemandwasanimprovementovermappingapplicationsasitprovidedcapabilitiesforoverlay,measurement,digitizing/scanning,supportedanationalcoordinatesystemthatspannedthecontinent,codedlinesasarcshavingatrueembeddedtopology,anditstoredtheattributeandlocationalinformationinseparatefiles.Itsdeveloper,geographerRogerTomlinson,hasbecomeknownasthefatherofGIS.

CGISlastedintothe1990sandbuiltthelargestdigitallandresourcedatabaseinCanada.Itwasdevelopedasamainframebasedsysteminsupportoffederalandprovincialresourceplanningandmanagement.Itsstrengthwascontinent-wideanalysisofcomplexdatasets.TheCGISwasneveravailableinacommercialform.ItsinitialdevelopmentandsuccessstimulatedvariouscommercialmappingapplicationsbeingsoldbyvendorssuchasIntergraph.

Thedevelopmentofmicro-computerhardwarespurredvendorssuchasESRI,MapInfoandCARIStosuccessfullyincorporatemanyoftheCGISfeatures,combiningthefirstgenerationapproachtoseparationofspatialandattributeinformationwithasecondgenerationapproachtoorganizingattributedataintodatabasestructures.

The1980sand1990sindustrygrowthwerespurredonbythegrowinguseofGISonUnixworkstationsandthepersonalcomputer.Bytheendofthe20thcentury,therapidgrowthinvarioussystemshadbeenconsolidatedandstandardizedonrelativelyfewplatformsanduserswerebeginningtoexporttheconceptofviewingGISdataovertheInternet,requiringdataformatandtransferstandards.

3.WhatmakesupaGIS?

AworkingGISintegratesfivekeycomponents:

hardware,software,data,people,andmethods（Fig.2）. 

HardwareisthecomputeronwhichGISsoftwareprovidesthefunctionsandtoolsneededtostore,analyzeanddisplaygeographicinformation. 

Geographicdata（layers）andrelatedtabulardataarenecessaryinordertoperformworkinaGISsoftware. 

GIStechnologyisforlimitedvaluewithoutthepeoplewhomanagethesystemanddevelopplansforapplyingittoreal-worldproblems. 

Fig.2GISkeycomponents

Lastly,asuccessfulGISoperatesaccordingtowell-designedplansandbusinessmethods,whicharethemodelsandoperatingpracticesuniquetoeachorganizati