ARCGIS最短路径 VB代码 - 图文

毕业设计（论文）专用纸frommanysourcestoasingledestination.Iftheshortestpathbetweenanytwopointsisastraightline,thentheleast-costpathisthepathofleastresistance.Least-costpathanalysisusesthecostweighteddistanceanddirectionsurfacesforanareatodetermineacosteffectiveroutebetweenasourceandadestination.CriteriaforAnalysis:

Acostpathconsistsofsequentiallyconnectedlinksthatprovidetherouteforeachcelllocationtoreachasourcecell.Acostpathdistance(orcostdistance)fromanycelltoasourcecellistheaccumulativecostofalllinksalongthepathforthecelltoreachthesourcecells.Therearemanypossiblepathstoreacheachsourcecell,andtherearemanypathstoreachthemanysourcecells.Thereisoneleast-costpath,dependinguponthemodelcriteria.TofindtheleastcostpathforaproposedroutepipelinebetweentwoSabkhasinShaybahfield(SabkhaA&SabkhaB).Todothatwewillhavetokeeptheconstructioncostdown,minimizingsluggingandbackpressureofoilandalsoavoidsurfacefacilities.Thefollowingobjectivesaretobeconsidered;Theleast-costpathshouldbeprimarilycomposedoflandwithashallowslopebecausesteepterrainwillincreasetheoperatingcost.Thelongerthepath,thehighertheconstructioncosts;therefore,thedistancebetweenthetwositesneedstobeconsidered.ThefirststeptowardsleastcostpathanalysisistheconversionofcontourdatatoDigitalElevationModel(DEM)usuallydonethroughArcGISSpatialAnalystExtension.TheDEM(digitalelevationmodel)isarasterversionofthecontourdata.ThesourceofcontourdataisSurveyingServicesDivision(SSD)ofSaudiAramco.DerivingSlopeMap:

37毕业设计（论文）专用纸TheSlopehelpstoidentifythemaximumrateofchangeinsurfacevalueoveraspecificdistance,anditisexpressedindegreesorpercentage.CalculatingtheslopeisoneofmanyfunctionsofthespatialanalysttoolandthisfunctionwasusedtoderiveaslopemapfromDEM.Fig2:SlopeMapReclassSlopeMap:

TheSlopemapwasreclassifiedonascaleof1to10.Thedarkershadesrepresentareasofshallowslope,areaswhereconstructioncostswillbelessexpensive.Theresulthelpstodifferentiatetheslopeclassesandhenceprovideanopportunitywhenchoosinglocation.Fig3:ReclassMapCreatingTotalCostLayer:

Thedarkershadesindicateareasthroughwhichitwillbelesscostlytoconstruct.Thisisanexampleofaversionoftotalcost.Wecanconsidervariouscombinationsofcontributingfactors,therebycreating38毕业设计（论文）专用纸severaltotalcostsurfacealternatives.CostDistanceandCostDirectionAnalysis:

Fig5:CostDistanceFig6:CostDirectionOncetotalcostlayeriscreated,weneedtoderivecostdistanceandcostdirectionsurface.Onesurfaceisincreasingcostsaswetravelfartherawayfromthesource.Theothersurfacemodelisincreasingcostsdependingonthedirectionwearetraveling.Bothofthesesurfacesactasinputstocalculatetheleast-costpath.TheCostDistancelayerrepresentshowcostsaccumulateaswemovefurtherawayfromtheoneoftheSabkhas.Thecostdistancelayertakesintoaccountdistancemeasurementsfromthesourceandthevaluesofthetotalcostlayerforeachlocationonthemap.Thecostdirectionlayertakesintoaccountthetotalcostlayeranddeterminesthebearingtothe39毕业设计（论文）专用纸easiest(leastcostly)pathbacktothesource.Whencombined,theselayersarelikeanobstaclecourse.Thefartherawayyouare,themoreitcostsyouintime,money,orefforttoreachthegoal.Least-CostPath:

Theleast-costpathdistancefromacelltoasourcecellisthesmallest(orleast)costdistanceamongallcostpathdistancesfromthecelltothesourcecells.Forshortestorleast-costpathanalysis,weidentifyatleasttwopointsorlocations:thesourceandthedestination.UsingArcGISspatialanalystwecanFig7:Source&DestinationPointsFig8:LeastCost-Pathgenerateleastcostpathasshownaboveandalsotheshortestpathfromthesourcetothedestinations.Theresultsindicatetheoptimumroutebetweentwopoints.Theseroutesarefurtherutilizedinthepetroleumindustryforrunning40