天空角系数的计算

GöteborgUrbanClimateGroupUniversityofGothenburgDepartmentofEarthSciencesSkyViewFactorCalculatorUserManual-Version1.1Date:20100610FredrikLindberg,BjörnHolmerUniversityofGothenburgcontact:[e-mail]describeshowtoinstallandmakeuseoftheSkyViewFactorCalculatorthatisabletocomputetheSkyViewFactor(SVF)onhemisphericalphotographsusingaGraphicalUserinterface(GUI).AdetaileddescriptionofthecalculationproceedingscanbefoundinHolmeretal.(2001)andinJohnson&Watson(1984).Thissoftwareisfreetouse.VersionhistoryV1.1ThisversionnowcalculatesSVFusingtwodifferentmethods.Firstthepixel-basedmethoddevelopedbyHolmeretal.(2001)andtheannulusmethodaspresentedinJohnsonandWatson(1984).Thecalculationprocedureforannulusmethodmakeuseof45annuliwitha5degreeazimuthintervalresultinginthat3240pixelsinthehemisphericimageisusedinthecalculation.Thepixelmethodincludesallpixelswithintheradiusoftheimage.Thisresultsforexampleinapproximately404000pixelsthatisexaminedina720x720pixelimage.Figure:Blackdotsrepresentsthepixelsinvestigatedusingtheannulusmethod.Severalbugsarealsocorrectedinthisversionandresultscannowoptionallybewrittentoatextfilecalled‘SVF_results.txt’thatwillbesavedinthesamefolderasthecalculatorisexecutedfrom.Ifseveralimagesisexamined,newresultswillbeappendedinthesametextfile.V1.0Firstversion.Released2010-10-20InstallationThismodeliswritteninMATLABcomputinglanguageandisexecutedusingtheMATLABCompilerRuntime(MCR),whichcanbedistributedroyaltyfree.Hence,theusercanrunthemodelwithouthavingaMATLABlicenseoranyskillsinMATLABprogramming.TheMCRrunsonWINDOWSNT/2000/XP/Vista7platforms.TobeabletorunthemodeltheMCRmustbeinstalledlocallyonthecomputerthatwillbeused.TheMCRandtheSVFcalculatorcanbedownloadedfrom:–Loadingimage:Fileformatspossibleforimagefilesare*.jpg,*.png,*.gif,*.tifor*.pgm.2.STEP2–Specifyradius:Inordertocomputetheradiusandthecenterpoint(redstarinthefigurebelow)oftheimage,threepointonthecircumferencelinehastobespecified(redcrossesinthefigurebelow).Clickonthe“Specifyradius”andmoveyourmousepointerovertheimage.Itwillturntoacrossandnowyoucanclickonthreeseparatelocationsonthecircumference.3.STEP3–Convertingimagetoblackandwhite:skyandnon-skypixelshastobeseparated.Tomakethisseparationasgoodaspossibleaslide-barisavailable.Makesurethatallskypixelsarecorrectlyclassified.4.STEP4–Manualcorrectionofnon-skypixels(optional):Usually,lightareassuchaswindowsandwhitewallsisclassifiedasskyandthishastobecorrectedinordertoobtaincorrectSVF-values.Ifyouhaveareasthatarewrongclassified,clickonthe“Fillnon-skyregions”,moveyourmousepointerovertheBW-imageandthepointerwillturnintoacross.Fillregionswhereyouhavewrongclassifiedbyinsertingverticesofapolygonasshowninthefigurebelow.Tofinishapolygon,clickonthefirstverticesinthepolygonandfinallydoubleclickinthepolygon.Youcanfillasmanypolygonsaspossiblebyjustclickingthe“Fillnon-skyregions”-buttonagain.5.STEP5–CalculateSVF:ClickontheCalculateSVF-buttonandtheSVF-valuewillappearbelowtheimagecalculatedbythemethodsmentionedabove.AdditionalsettingsTherearethreeadditionalsettingsthatcouldbemade.Somefisheyelensesdonothave180degreefieldofview.Thereforeanoptiontochangethisisincluded.Also,anoptiontoprocessmorethanoneimagefromthesamecamerasystemisavailable.Anewoptionwheretheresultsiswrittentoatextfileisalsoavailable.ReferencesB.Holmer,U.Postgård,andM.Eriksson(2001).SkyviewfactorsinforestcanopiescalculatedwithIDRISI.TheoreticalandAppliedClimatology68,33-40JohnsonG,WatsonI(1984).TheDeterminationofView-FactorsinUrbanCanyons.JournalofClimateandAppliedMeteorology23,329-335