SpatialDataStructureInGIS

1SimpleunderstandingofthespatialdatastructureaboutGISAbstract:Thespatialdatamodelandspatialdatastructureisthecenterofthegeographicinformationsystem(GIS)ofthesubjectcontent.Thispaperhascarriedontheinductionandsummaryofresearchofthedefinitionandclassificationofspatialdatastructure.Keywords:GIS,spatialdatastructure,vectordata,rasterdata0.IntroductionInGISspatialdatastructureandspatialdatamodelarecloselyrelated.Theestablishmentofthedatamodelmustpassacertaindatastructure,butithasaverybigdifferencebetweenthem.Datamodelisaconceptthatistherealofartificialconceptualization,istoextracttherealworld,istheunderstandingandchoiceoftherealworld.Datastructurewhichitmeanstherelationshipbetweeneachelements,accordingtothecharacteristicsofthespatialdatastructureanddatamodelandtheirrelations,itcanbuildaspatialdatabasesystem.1.ThedefinitionofspatialdatastructureSpatialdatastructureisacollectionofspacedataunit.Thedataunitisthebasicunitofdata,whichcanhaveafewitems,andtherelationshipbetweendataunitiscalledastructure.So,researchonspatialdatastructurewhichitmeanstherelationshipbetweenthespacetarget,includinggeometryandnon-geometryrelationship.Datastructureisaexpressionofdatamodel,whichoftenshowsthroughaseriesofcharts,matrix,andthedatarecordsofcomputercode.2.Theclassificationofthespatialdatastructure2.1Vectordatastructure2.1.1DefinitionVectordatastructureisbasedonthevectormodel,usingdot,line,faceoftheEuclideangeometryanditscombinationtorepresentthespatialdistributionofgeographicalentity.Itisthewaybyrecordingthecoordinate,asaccurateaspossibletoshowgeographicalentitiessuchasthepoint,lineandpolygon.Thelocationofthenaturalgeographicalentityuseitsspacepositioninthecoordinateframeofreferencetodefineandcoordinatespaceiscontinuous.Allowinganypositionoflengthandareatodefineprecisely,itscharacteristicispositioningandattributeimplied.GISusethemodelofthevectordatastructure.Itabstractthegeologicalentitiesofspaceasdot,lineandfacethreekindsofgeometricelements.Vectordatastructureexpressrelationofspatialentitiesbyoptimizingthetopology,andestablishthebasicframeworkforspatialdatabase.22.1.2CharacteristicsAdvantage:Thedatashouldbeorganizedasaunitaccordingtothepoint,lineorpolygon,structuresimple,intuitiveandeasytoimplementwiththecomputinganddisplaybysinglebitforentity.Disadvantages:A.Thepublicedgeofadjacentpolygonsisdigitizedandstoredtwicebythewayofindependentstorage,andappearingdataredundancyandfinelypolygon,leadtotheinconsistentdata;Pointdictionarystorageensurestheuniquenessofpublicedge.B.Vectordatastructurecreateasystemofitsownthatabsencethepolygonofadjacentinformation,neighborhoodprocesscomplexlyandneedtotrackthepublicside.C.Processingnestingproblemsaremoretroublesuchasislandorhole,needtocalculatepolygoninclusion.2.1.3TopologicalrelationsofvectordataAsisknowntoall,spaceanalysisisthecharacteristicsfunctionofGIS,sointheGISspatialdatastructurenotonlydescribethegeometricalcharacteristicsofthespatialobjectitself,butalsodescribethetopologicalrelationsbetweenspatialobjects.Weadopttopologicaldatamodelwhichisbasedonakindofsegment.Topologymodelisthatdirectlystoresometopologicalrelationsanddot,lineandpolygonbetweenentitiesinthetable,andthereisnodataredundancy.Throughthistable,youcaneasilyjudgetheconnectingrelationofthelinearentityandtheadjacencyrelationsoftheplanarentities.Thismodelhasstrongabilityinthespatialdataorganization,intheexpressionoftopologicalspatialrelations,inthetopologicalconsistencycheckingofthedatamodelandingraphicsrecovery,thereforetheyarewidelyusedinGISsoftware,suchasArcInfo.Butwhenthismethodwasusedtoconstructanewtopologicalspatialrelations,needalargeamountoftime.2.1.4NotopologicalrelationshipofvectordataVectordatamodelofnotopologicalrelationshipalsocallednoodlesdatamodel,itonlyrecordsthespacetargetcoordinatesandattributesinformation,anddonotrecorditstopologyrelation.Itmayhavetwoforms:oneisthateachdot,lineandfacetargetdirectlyfollowitsspacecoordinates;Anotherwayisthatpointcoordinatesasafile,lineandpolygoniscomposedofthedot.Inthefirstform,thecoordinatesofeachentityarestoredseparately,withoutconsideringtheadjacentpolygon,lineandpoint.Whenusingthismethod,inadditiontotheoutercontourline,polygonboundarydataareobtainedandstoredtwice,andthiscanproducecrackoroverlap,andgeneratedataredundancy.Inordertoeliminatecracks,generalneedtoedit.Inordertoovercomesomelimitationsoftheindependententitycode,somesystemisestablishedwhichbasedonthesharepointdictionary.Pointdictionarycontainsthecoordinatesofeachboundarypointonthemap,thenestablishboundarytableofaentitypoint,lineandpolygon,whichismadeupofpointnumber.Point3dictionarymethodisusedtoestablishapointdictionarydatafilewhichcaneliminatethepolygonboundarycracksandrepetitionstoreofthecoordinatedata,buttheystilldidnotestablishspatialrelationshipsbetweentheeachpolygonentities.2.2Rasterdatastructure2.2.1DefinitionRasterdataisthesimplestandmostintuitivespatialdatastructure,itcoulddividegroundintohomogeneousgrid,eachgridasapixel,thepositionofapixelisdeterminedbytherowandcolumnnumber,thecodewhichpixelcontainsindicatesitsatt