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1、Lab3：ExploringDigitalData(数字数据)Notethatthereisaworksheetattheendofthislabwrite-upthatyoumustturninattheendofthelabperiod.Modernremotesensingusesdigitaldata,soitiscriticalthatyouunderstandwhatthismeanssoyoucanmanipulatedigitalimages.Evenimagerycollectedusingfilmisusua
2、llyconvertedtodigital(seanned)sothatitcanbemanipulatedonthecomputer.Asyoulearnedinlecture,thefundamentalprocessingunitindigitalimageryisthepixel.Eachpixelrepresentsanareaontheground,thesizeofwhichisdeterminedbythespatialresoluUonofthesensor.Inimagery,eachpixelisdescr
3、ibedbyadigitalnumber(DN)thatrepresentstheamountoflightthattraveledfromthepixelareaonthegroundtothesensor(satelliteorairborne"camera").ADNisusuallyaunitlessindexofanamountoflight,notactualradianee.Thecollectionofpixelsfromasensorcoversanareaontheearthrepresentedbythei
4、mage.Thewidthoftheimageisdeterminedbytheswathwidthofthesensor.Sensorsusuallycollectimageryincontinuousnorth-southswathssotheheightofanimageisdeterminedbyhowthedatagetcutintopiecesaftercollection.Typically,imageryisdividedintosquarepieces,sothattheheightisthesameasthe
5、swathwidth,butthisisrftalwaysthecase.Finally,sensorsoftencollectdataacrossmultiplewavelengthsoflight(e.g.,visibleblue,green,red,near-infrared,etc.).Eachwavelengthregioncapturedbythesensorisstoredinaseparateimagelayerorband(sometimescalledachannel).Atypicalsatelliteim
6、ageislikealayercakewithbandsforlayers.Ifasensorhas6bands,eachplaceonthegroundwillberepresentedby6digitalnumbers,oneforeachband.Collectively,thesedigitalnumbersdescribethepatternofreflectanee(complicatedbytheatmosphere)fromtheareaonthegroundcoveredbyeachpixel's"footpr
7、int."Intoday'slab,youwillcontinueexaminingdigitalsatellitedataandbeginlearningsomesimpleimageprocessing.ThegoalisfortheconceptsofDN's,bands,andimagestobecomeintuitivetoyou.(木次实验主要了解DN值、波段的概念以及一些简单的影像处理。)1.StartENVIandopentheimagecalledTestDataO.ThisisalmostthesameLan
8、dsat5imagethatyouhaveusedbefore.(丿J动ENVI,打开卜发的示例数据TestDataOo)RecallthatLandsat5hasthreevisiblebands(B,G,R=1,2,3),anear-infraredband
