微波遥感简介(英文)课件

FundamentalforSARRemoteSensingFundamentalforSARRemoteSenPassiveremotesensing–ActiveremotesensingPassivesystemOpticalsensorsActivesystem

radarsensorsPassiveremotesensing–ActiRADAR=RAdioDetectionAndRanging,radar=arangingordistancemeasuringdevicewithatransmitter,areceiver,anantenna,andanelectronicssystemtoprocessandrecordthedata.Transmittergeneratessuccessiveshortbursts(orpulsesofmicrowave(A)atregularintervalswhicharefocusedbytheantennaintoabeam(B).Theantennareceivesaportionofthetransmittedenergyreflected(orbackscattered)fromvariousobjectswithintheilluminatedbeam(C).RADAR=RAdioDetectionAndRRadarandelectromagneticspectrumRadarandelectromagneticspecRadarsignal:amplitudeandphaseSARsignalisacomplexnatureSAR=Amplitude+phaseSpeckleappearsasagrainy"saltandpepper"textureinanimage.Thisiscausedbyrandomconstructiveanddestructiveinterferencefromthemultiplescatteringreturnsthatwilloccurwithineachresolutioncell.HomogeneoustargetConstructiveinterferenceDestructiveinterferenceVariouslevelofinterference(betweenconstructiveanddestructive)Radarsignal:amplitudeandphSignal-Surfaceinteractionsandback-scatteringMicrowaveinteractionwithnaturalsurfacesisafunctionof:SARconfigurationincidenceanglefrequencypolarisationSurface

’sphysicalandelectricalpropertiesroughnesssoilmoisturevegetationparametersSurface

’sgeometryLocalandlargescaleSignal-SurfaceinteractionsSignal-Surfaceinteractions:Rayleighcriterion

Specularreflection(smoothsurface)

h<λ/8cosθDiffusereflection(roughsurface)

h<λ/8cosθλvariesfromK1cmX3cmC5.6cm

S10cmL23cmP70cmRADARSATERSENVISATSpeculartodiffuseSignal-Surfaceinteractions1-Backscatteroveraroughsurface(1):

=>radarresponseduetobackscatteredsignal2–Penetrationinadrysoil(2):

responsedependsuponsubsurfacelayer3-Smoothsurfaceorasuper-saturatedsoil(3):

Specularreflection=lowradarresponseNote:influenceofradarwavelengthand

incidenceangleInteractionoftheRadarSignalwiththeSoil1-BackscatteroveraroughReflectionoffforestcanopy(1)Penetrationintofoliage(2)(volumescattering)Multiplereflectionsontreesandsoil(3)BackscatterofRadarSignaloverForests

Reflectionoffforestcanopy(1-Lowincidenceangleandshortwavelengths(1)=>:nopenetrationintovegetation2-Strongincidenceandlargewavelengths(2):=>penetrationintovegetation=>informationonmoisture,soiland/orwater3-Specifictemporalbehavior

ofcertaincroptypes(e.g.rice)Backscatterbehaviorovervegetation1-LowincidenceangleandshRadarsignal-surfaceinteractionsFree(liquid)water=smoothsurface Urbanarea=roughsurface Ploughedfields=roughsurface Cropatearlystage=smoothsurface darkbrightdarkbrightRadarsignal-surfaceinteracSAR:GeometryofIlluminationSAR:GeometryofIlluminationSyntheticAperturePrincipleSyntheticAperturePrincipleSARspatialresolutionfauchéeh

i

AntenneduradarRangeresolution

ihLa

adraAzimuthresolution:determinedbytheangularwidthoftheradiatedmicrowavebeamandtheslantrangedistanceSARspatialresolutionfauchéehRadarImagedistortion:Slant-rangescaledistortion

Radar=measurethedistancetofeaturesinslant-rangeratherthanthetruehorizontaldistancealongtheground.avaryingimagescale,movingfromneartofarrangeTargetsA1andB1:samesizeontheground,Differentapparentdimensionsinslantrange(A2andB2)

Targetsinthenearrangetoappearcompressedrelativetothefarrange.Usingtrigonometry,ground-rangedistancecanbecalculatedfromtheslant-rangedistanceandplatformaltitudetoconverttotheproperground-rangeformatRadarImagedistortion:Slant-ABCDImagebrightnessEffectoftopography:-Shadows-Foreshortening-Layover(extremecaseofforeshortening,topographyisinverted)=>SARuselimitationsinreliefareaShadowUseofDEMtocorrectA=Smaller=foreshorteningRADARGeometricDistortions:

Foreshortening-Shadowing-LayoverABCDImageEffectoftopographInfluenceofsystem’sconfiguration:polarizationPolarizationeffectsPolarization

Referstotheorientationoftheelectricfield

Transmitmicrowaveradiationeitherhorizontallypolarized(H)orverticallypolarized(V).Antennareceiveseitherthehorizontallyorverticallypolarizedbackscatteredenergy,andsomeradarscanreceiveboth.Fourcombinations:HH-forhorizontaltransmitandhorizontalreceive,VV-forverticaltransmitandverticalreceive,HV-forhorizontaltransmitandverticalreceive,VH-forverticaltransmitandhorizontalreceiveInfluenceofsystem’sconfigurInfluenceofsystem’sconfiguration:

polarizationandwavelengthPolarizationeffectsCLWavelengtheffectsInfluenceofsystem’sconfigurComparisonofopticalandSARdataOPTICAL«Biological»Sensitivity(ex:photosynthesis)HighResolutionSpectralResolution(severalbands)RADAR«Physical»Sensitivity(ex:roughnessandmoisture)HighResolutionAllweatheracquisition(cloudpenetration)ComparisonofopticalandSARImageprocessingtechniquesofSARdataGeometriccorrectionandgeocodingCalibrationSpecklefilteringCoherenceimagesClassificationAmplitudeandphaseSARinformationImageprocessingtechniquesofQuantitative

analysisofSARdataPrerequisite:Calibration(documentedbyESA)MeasurementaccuracyERSsignalstability(+/-0.2dB)Observationscale

0

=f(roughness)*f(soilmoisture)*f(vegetationparameter)1date(1equation,severalunknownparameters??)

multi-date,synergywithothersensors,SIGPoorscientificknowledge“SARsignalinteractionwithnaturalsurfaces”QuantitativeanalysisofSARdSARdata:interestinginformation

DifficultytouseorextractSpeckleaffectingphoto-interpretationintroducinguncertaintyinthebackscatteringcoefficientmeasurementCombinedinfluenceofdifferentparametersonthebackscatteringcoefficientmeasurementandespeciallyroughness,biomassandmoistureComplexityoftheinteractionphenomenabetweentheSARsignalandnaturalsurfaceswhichisnotfullyunderstoodGeometryofSARsystemsSARdata:interestinginformaSARradiometrycorrection:SpecklefilteringandradiometricenhancementOftenaprerequisitebeforefloodmappingorbeforeclassificationSpatialfiltering:MeanfilterAdaptativefilterGamma-MAPLee,frostetc…

Temporalfiltering:-Annualsumming-Seasonalsumming

Optimizedtemporalfiltering:3localparameters-Texturaldistance-Radiometricmean-Correlation(TemporalfilteringonSimages)SARradiometrycorrection:Oft

Optimizedtemporalfiltering

=takeinaccountlocalmeanj=1,…S.S=numberofimageinthetimeseriee,I=Intensityofthepixel(a,r),m=localmeanoftheneighbourhoodofthepixel(a,r),ak=weightingcoefficientoftheimage«k»with: oùSARradiometrycorrection:SpecklefilteringandradiometricenhancementOptimizedtemporalfilteringComparisonofmethodsGamma-MAPFilter(widowsize=3x3)

Simpletemporalmean,basedona7imagestimeserieOptimizedtemporalfiltering-ISARradiometrycorrection:SpecklefilteringandradiometricenhancementComparisonofmethodsGamma-MAPRadiometrycorrection:specklefilteringGammaMAPfilterRadiometrycorrection:speckleRadiometrycorrection:specklefilteringbytemporalfilteringOneERSimageResultofERStemporalsummingRadiometrycorrection:speckle1SARImage8SARimagesTemporalfusionatoolforclassificationenhancement1SARImage8SARimagesTemporaNotionofPhasecoherenceCoherencevalueisdefinedas:Thedegreeofcoherenceforeachpair(s1,s2)ofco-registeredcomplexvaluess1,s2isgivenby:<...>representsanaverage,whichisestimatedbythespatialaverageoverafinite-sizewindowPhasecoherenceiscloselyrelatedtothelocaldeviationofthephase

differentialPhasecoherenceprovidesinformationongeophysicalchangeoftheobservedtargetPhasedifferenceandcoherencePhasedifferencenotion:TwosignalofthesamewavelengthbutoneisdisplacedThedisplacementbetweencorrespondingpointsofthesignalareknowasphasedifference.

Phasedifferenceisprocessedtoobtainheightand/ormotioninformationotheEarthsurface.AsourceforSEMgenerationNotionofPhasecoherencePhasePhasecoherencesensitivityCoherencebylandcovertheme:

Highcoherence :baresoil,built-uparea,rocksModeratecoherence :vegetatedareas,cropsLowcoherence :forestedareasNocoherence :Waterbodies,majorchangeCoherenceisrelatedtoGeometryofthetargetAcquisitiongeometry(notionofbaseline)StabilityofthetargetbetweentwosuccessiveacquisitionsNotionofsuccessiveisbroad:canbesimultaneouswithtwodecaledantennas,ortwodays,revisittime,35daysforERS,etc..

PhasecoherencesensitivityCohSARcoherencedata:mutitemporalacquissitionCoherence,Amplitude,AmplitudeChangeinRGBSARcoherencedata:mutitemporMultitemporalSARcoherencedataandMulti-temporallanduseclassificationMultitemporalSARcoherencedaMicrowavesensorshistory1960'sFirstairborneradarsystems:SLAR1970'sFirstairborneSARsystems1980'sSpaceborneSARsystems:SEASAT,SIR-A,SIR-B DevelopmentofRadargrammetry1990'sManyradarsatellites:JERS-1,ALMAZforResearch ERS-1,ERS-2(Research/Commercial), RADARSAT(Commercial)Highlights:OceanandLandSurfacesapplications Commercialapplications DevelopmentofInterferometry

2000‘ENVISAT(Research/Commercial)Nearfuture:JapaneseALOS,CanadianRadarsat2/3,ItalianCosmoSkymed,GermanTerraSAR,ChineseSAR…Microwavesensorshistory1960'ERS-1/2CBand,VV,23oincidence100x100kmimagewith25mresolutionExtensiveglobalarchivesince91ERS-1/2CBand,VV,23oincidenRADARSATCBand,HH,20o-49oincidenceRangeofviewing(20beampositions)Rangeinimagecoverage(50x50to500x500km)Rangeinresolution(8-100m)LimitedarchivebutgoodprogrammingserviceRADARSATENVISATSARCBand,HH,VV,HV20o-49oincidenceRangeofviewing(beampositions)37differentandmutuallyexclusiveoperatingmodesinhigh,medium(WideSwathMode),Wideswathcoverage;405kmswathwith150mor1kmresolution.Resolution,30mto1kmDatatransfertpotentialcouplingwithArtemisENVISATSARENVISATSARImageMode

(IM)VVorHHpolarisationimagesfromanyof7selectableswaths.Swathwidthbetweenapproximately56km(swath7)and100km(swath1)across-track.Spatialresolutionofapproximately30m(forprecisionproduct).

AlternatingPolarisationMode(AP)Twoco-registeredimagesperacquisition,fromanyof7selectableswaths.HH/VV,HH/HV,orVV/VHpolarisationpairspossible.Spatialresolutionofapproximately30m(forprecisionproduct).

WideSwathMode(WS)400kmby400kmwideswathimage.Spatialresolutionofapproximately150mby150mfornominalproduct.VVorHHpolarisation.

GlobalMonitoringMode(GM)Spatialresolutionofapproximately1000minazimuthby1000minrangefornominalproduct.Uptoafullorbitofcoverage.HHorVVpolarisation.WaveMode(WV)Asmallimagette(dimensionsrangebetween10kmby5kmto5kmby5km)isacquiredatregularintervalsof100kmalong-track.TheimagettecanbepositionedanywhereinanImageModeswath.Uptotwopositionsinasingleswathorindifferentswathsmaybespecified,withacquisitionsalternatingbetweenoneandtheother(successiveimagetteswillhencehaveaseparationof200kmbetweenacquisitionsatagivenposition).HHorVVpolarisationmaybechosen.Imagettesareconvertedtowavespectraforoceanmonitoring.

ENVISATSARImageMode

(IM)VVoENVISATSARENVISATSARFutureVHRSARSensorsRADARSAT2(Nearfuture…launchscheduledforFebruary2002,April2003andNovember2005)dailyrevisitVHRSARmode3mALOS:Lband,PhasearrayTerra-SAR:constellationXband(potentiallyasecondconstellationLband)Cosmo-Skymed(2004-2006)4satellitesconstellation=>lessthan12hourrevisittimeVHRSARmode1-3mChineseXbandin2006SARVHR=>Moredocumentedandaccuratelandscapedescription=>Urbanfloodmapping=>LessconfusionbetweenfloodedareaandneighbourhoodFutureVHRSARSensorsRADARSATRADARSATIIStandardmode:25*25mUltraFinemode3*3mRADARSATIIStandardmode:25*2TERRA-SARXLaunchscheduledforMarch2005(10-02-04)TERRA-SARXLaunc