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-211-1234立利立利立立利X-band雷流利雷流流不流流流了浪流行浪流列流流率良97%GPS流量流行雷流SurfaceCurrentExtractionfromShallowWaterRadarImagesChia-FengLinLi-ChungWuDong-JiingDoongChia-ChuenKaoABSTRACTItispossibletoextractesurfacecurrentinformationfromtheX-Bandradarbackscatter.Thevalueofrepresentativewaterdepth(RWD)isoneofthemostimportantfactorsintheimageprocesstoderivesurfacecurrentfromradarimages.Itcannotbeignoredforthecaseoftheimageisfromshallowwaterarea.ThepurposeofthispaperwastostudytheestimationofRWDinordertofindthecorrectseasurfacecurrent.Inadditiontothefieldexperiment,animagesimulationmethodwasdevelopedtosimulateimagesforfurtherstudiesfromvariousconditionsofwaterdepths,wavesandcurrents.TheRWDwastestedfromthewaterdepthrangesthattheimagecovers.TheoptimalRWDwasthendeterminedbythecriteriaonminimabiasofinputandanalyzedcurrents.TheresultshowsthattheoptimalRWDvaluehascorrelationwithbathymetryslope.Byregressionanalysis,thecoefficientofcorrelationis97%.AnempiricalformulaisthereforederivedtoestimatetheRWD.Inordertoobtainvalidityoftheresultfromimagesimulation,afieldexperimentwasarranged.SeasurfacecurrentmeasuredfromGPSbuoywasusedforvalidationofpresentformula.ItwasshownthattheresultofseasurfacecurrentderivedfromradarimageswasimprovedbyinputtingtheRWD28論立2006年11Proceedingsofthe28thOceanEngineeringConferenceinTaiwanNationalSunYat-SenUniversity,November2006-212-estimatedfromtheempiricalformulainthisstudy.Theimprovementissignificantatthecoastalareawithsmallrelativewaterdepth.都流料參流類數里不論流參流(in-situmeasurement)(remotesensing)兩不X-band雷雷拉流都勒浪理論流量流流略tanh(kd)不不參數來10.5度論流流00.10.20.30.40.50.600.20.40.60.811.2d/Loω2/gk1理論雷量料力雷雷度流不列2利利葉理論列(Youngetal.,1985)利濾浪濾(Doong,2001)浪理論數率(1)UkdkkgKKKK⋅+=ω)tanh((1)dkK數量ω率g力度),(yxUUU=K流量都勒132...YX132...YXT132...YX132...YXT2切雷列(1)數率量喇狀(Doong,2001)流都勒狀3不流數率浪喇狀量來理論浪量(3)3不來浪量濾流利列量(Youngetal.,1985)Gangeskar(2002)利-213-流流(2)行),,()(02ω∑∑∑ω∆=ω=ω−=−=yxkkkkkkkEJMNxxxNyNyky(2)yyxxUkUkkkg−−−ω=ω∆d)tanh(GG(3)),,(ωyxkkE列量xUyUxy量流(3)理(4)⋅⎥⎥⎥⎦⎤⎢⎢⎢⎣⎡∑∑∑∑=⎥⎥⎦⎤⎢⎢⎣⎡−122yyxyxxyxEkkEkkEkEkUU⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎣⎡∑−ω∑−ωyxkdkkgEkdkkgE))tanh(())tanh((KGKG(4)若1)tanh(≅dkK雷流流流了流度(Wuetal.,2005)-0.4-0.3-0.2-0.100.10.20.30.400.511.522.53wavenumber[rad/m]frequency[rad/s]U=0m/sU=1m/sU=2m/s3不流數-率量料切利數來行利不浪不(5)])sincos([cos),,(miiimimMmimIiyxktayxtε+θ+θ−ω∑∑=ηK(5)ima浪mik浪數(wavenumber)miω率miε(0~2)JONSWAP(Goda,1999)來易數(6)),()(),(θ=θfGfSfS(6))(fS率),(θfG數(7)imimmiffSaθ∆∆θ⋅=),(2(7)切率率浪率流流流利理論不數流念度利(8)),(yxd利數UkyxdkkgmimimimiKKKK⋅+=ω),(tanh(8)xy度7.5m128128pixels1.67s度53s32雷雷參數4(a)例11s454(b)-214-Xdirection(pixel)Ydirection(pixel)2040608010012020406080100120Xdirection(pixel)Ydirection(pixel)204060801001202040608010012050556065(a)(b)4(a)例(b)數流列利流不流流5不度列流流流利5downdupd率流率率利不浪率率率1/70流0.02m/s利參數來60Lmind率inputddowndupddowndupd兩流參數6度率1率6率1/2000~1率來7度不行率1/1500~1/206率(9)1+10.9+157=dd2mininputSS⋅⋅(9)mindS率inputd流不論率率(9)列列流),,(yxtη),,(yxkkEω),(yxuu流n=n+1yesnodndd∆⋅+=mindowndmdd∆⋅−=maxup流),(yxuuyesnom=m+1列列流),,(yxtη),,(yxkkEω),(yxuu流n=n+1yesnodndd∆⋅+=mindowndmdd∆⋅−=maxup流),(yxuuyesnom=m+15利流00.10.20.30.40.50.60.7dmin/L000.10.20.30.40.50.60.7dinput/L0inputddowninputdupregressionline6率流參數-215-00.010.020.030.040.05slope012345dinput/dminT=5secT=6secT=7secT=8secT=10secT=12sec0.97=R1+S10.9+S157=dd2mininput⋅⋅00.010.020.030.040.05slope012345dinput/dminT=5secT=6secT=7secT=8secT=10secT=12sec0.97=R1+S10.9+S157=dd2mininput⋅⋅7率5-1GPS流量流2006年5行GPS流雷行雷度15m100m4km雷GPS流料8GPS流量1m流流雷流流2%~3.5%(Wu,1975Gangeskar,2002)流度異料2-3m/s浪5-65-2雷流流GPS流量流流1兩來0.2~0.7GPS流量行流度兩料了17%28%0.4~1.2GPS流量行流度料了3.5%2%4.5%料論雷流流GPS流量流流流度1流流雷流(m/s)(雷/GPS)流10.38/0.580.48/0.5817%#10.2~0.720.37/0.640.55/0.6428%10.44/0.540.46/0.543.5%20.41/0.470.42/0.472%30.38/0.420.4/0.424.5%#20.4~1.240.39/0.340.41/0.34-8-216-流不流行浪流列流流率良97%GPS流量流行雷流(NSC94-2611-E-006-002)利利雷料1.Doong,D.J.(2001),UncertaintyAssessmentofWaveRemoteSensing,P.H.DThesis,NationalChengKungUniversity,Tainan.2.Dugan,J.P.andPiotrowski,C.C.(2003)“SurfaceCurrentMeasurementsUsingAirborneVisibleImageSeries,”RemoteSensingofEnvironment,Vol.84,pp.309-319.3.Gangeskar,R.(2002)“OceanCurrentEstimatedFromX-BandRadarSeaSurfaceImages,”IEEETransactionsonGeoscienceandRemoteSensing,Vol.40,No.4,pp.783-792.4.Goda,Y.(1999)“AComporativeReviewontheFunctionalFormsofDirectionalWaveSpectrum,”CoastalEngineering,Vol.41,No.1,pp.1-20.5.Seemann,J.,Senet,C.M.,Wolff,U.,Hatten,H.andZiemer,F.(2000)“HydrographicParameterMapsRetrievedFromNauticalRadarImageSequencesofInhomogeneousWaterSurfaces,”ProceedingsofGeoscienceandRemoteSensingSymposiumIGARSS2000,Vol.5,pp.1898-1900.6.Senet,C.M.,Seemann,J.andZiemer,F.(1997)“AnIterativeTtechniquetoDeterminetheNearSurfaceCurrentVelocityfromTimeSeriesofSeaSurfaceImages,”ProceedingsofOCEANS'97.MTS/IEEEConference,Vol.1,pp.66-72.7.Senet,C.M.,Seemann,J.andZiemer,F.(2001)“TheNear-surfaceCurrentVelocityDeterminedfromImageSequencesoftheSeaSurface,”IEEETransactionsonGeoscienceandRemoteSensing,Vol.39,No.3,pp.492-505.8.Wu,L.C.,Doong,D.J.,Kao,C.C.andTseng,C.M.(2005)“WaveandCurrentFieldsExtractedfromMarineRadarImages,”ProceedingsofthefifthInternationalSymposiumonOceanWaveMeasurementandAnalysis(WAVES2005)