Geographic Information System.docx
《Geographic Information System.docx》由会员分享,可在线阅读,更多相关《Geographic Information System.docx(12页珍藏版)》请在冰豆网上搜索。
![Geographic Information System.docx](https://file1.bdocx.com/fileroot1/2022-10/27/98d0e1aa-25b1-4f71-9be3-1cde666a8102/98d0e1aa-25b1-4f71-9be3-1cde666a81021.gif)
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