S技术在水利工程中的应用-遥感.ppt

RemoteSensing遥感,RemoteSensing,LastLectureAbsorptionfeaturesVegetationSoilsRocksandmineralsWater,iceandsnowConclusions,LastLectureEMRwhichhasinteractedwithmatterwillbedeficientinsomewavelengths,duetoabsorptionprocessesoccurringatatomicormolecularscalesTheseabsorptionfeaturescreatedistinctive“spectralsignatures”fordifferentEarthsurfacetypesThesecanbeexploitedby“multispectral”remotesensingmethodsformappingandmonitoringpurposes,RemoteSensing,SpectralSignatures,RemoteSensing,RemoteSensing,地表任一点反射的电磁波被分解为若干个波段，每个波段有一个反射率,RemoteSensing,反射率的大小用灰度表示，并被转换成数字信号，通常是28（0-255）,Grass,GREEN,BLUE,GREEN,RED,BLUE,GREEN,RED,NEARIR,NearIR,BandPlacement,BandDisplay,Band1,Band2,Band3,Band4,Band5,Band7,BLUE,GREEN,RED,NEARIR,SHORTWAVEIR,MID-WAVEIR,NEARIR,ColorTheory,Allcolorscreatedfromadditiveprimarycolors:RedGreenBlueComplementarycolors:MagentaYellowCyan,MultispectralDisplay,BandCombination=,7,4,2(LANDSAT),ColorGuns=,BandCompositeOutput=,Band3VisibleRed,Band2VisibleGreen,Band1VisibleBlue,IndividualLandsatBands,AppliedtoColorGuns,ResultingImage,Band4NearInfrared,Band3VisibleRed,Band2VisibleGreen,IndividualLandsatBands,AppliedtoColorGuns,ResultingImage,AVRISHyperspectralCube,AirborneVisible/InfraredImagingSpectrometer224spectralchannels4002500nmspectralresolution,20metergroundresolution.,BrineShrimppond,Sensing,Each“cell”recordedasa“digitalnumber”(DN)or“brightnessvalue”MeasuresamountofEMradiationThebrighterthesignal,thehigherthevalue.,Pixels,Eachcelliscalleda“pictureelement”,orpixelEachpixelrepresentsasinglebrightnessvalueforaspecificgeographicalarea,225204188146,214198169152,202200178162,icolumns,jrows,ixj=4x4=16pixels,114,109,101,97,SensorProperties,SpatialresolutionSpectralresolution/#bandsRadiometricresolutionTemporalresolution,Source:NASA,SpatialResolution,Measureofthesmallestangularorlinearseparationbetween2objectsthatcanberesolvedbythesensorInpractice,sensorsystemsnominalspatialresolutionisthedimensioninmeters(orfeet)onthegroundprojectedinstantaneousfieldofview(IFOV)Generally,smallerspatialresolutiongreatertheresolvingpowerofthesensorsystem,SpatialResolution,IKONOS4m,Landsat30m,DOQ0.5m,SpaceImaging,(cont.)SpatialResolution,Usefulrule:Todetectafeature,thespatialresolutionofthesensorsystemshouldbelessthanthesizeofthefeaturemeasuredinitssmallestdimension.,SpectralResolution,NumberandsizeofthebandswhichcanberecordedbythesensornominalspectralresolutionCoarsesensitivetolargeportionofemscontainedinasmallnumberofwidebandsFinesensitivetosameportionofemsbuthavemanysmallbandsGoalfinerspectralsamplingtodistinguishbetweensceneobjectsandfeaturesMoredetailedinformationabouthowindividualfeaturesreflectoremitemenergyincreaseprobabilityoffindinguniquecharacteristicsthatenableafeaturetobedistinguishedfromotherfeatures.,SpectralResolution,theSPECTRALresolutiondefinestherangeoflightstoredintheimageAblackandwhitephotographstoresavisiblelight;ithasonechannelthatstoresthelightfor0.4to0.7micrometersAnaturalcolorimagestoresreflectedred,blueandgreenlightindifferentchannels;e.g.0.45-0.52mmforblue,0.52-0.60mmforgreenand0.63-0.69mmforredALANDSATimagecontains7channnelsasdescribedabovethatstorereflectedlightotherthanvisiblelight.AHYPER-SPECTRALimagecontainshundredsofchannels.E.g.Ahyperspectralimagethatcollectsvisiblelightmaydividethevisiblelightrangeinto300channels,eachchannelcontaininganarrowrangeofwavelengths.,SpectralResolution/#Bands,NIR,SWIR,LWIR,SWIR,Multi-spectral,SpectralResolution/#Bands,RadiometricResolution,theRADIOMETRICresolutiondefinestherangeofvaluesthatanindividualpixelcanhaveReferstothesensitivityofthesensortoincomingradiance.Typicaldigitalimageshavearangeofvaluesfrom0255(atotalof256possiblevalues).Animagethatjusthasblackorwhitepixelswouldonlystore0(black)or1(white).RADARimageshaverangefrom0to4.3x109.,RadiometricResolution,TemporalResolution,Howoftentheremotesensingsystemrecordsimageryofaparticulararea.ExamplesLandsat18daysSPOT26days,TemporalResolution,2752Kmat,theEquator,185Km,Orbit1,Day1,Orbit2,Day1,Orbit1,Day8,Orbit2,Day8,Landsat,Trade-Offs,AerialPhoto,IKONOS,Landsat,SpaceImaging,Spatialandtemporalrequirementsforremotesensingapplicationsinagriculture.,Resolutionrequirementsfordifferentapplications,SummaryofResolution,Byincreasing1oranycombinationoftheseresolutions,increasechanceofobtainingre