Landsat TutorialWord格式.docx
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Landsat TutorialWord格式.docx
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ReturnBeamVidiconsandMulti-SpectralScannerSystemswereflownonthefirstthreeLandsats.
TheMSSprovedtobeamoreusefulandreliableinstrumentthattheRBV.
Landsats-4and-5wereequippedwithanMSSandanimprovedversionoftheMSS,theThematicMapper(TM).
Landsat-6carriedan"
EnhancedThematicMapper"
(ETM)only,andLandsat-7iscarryingan"
EnhancedThematicMapper-plus,"
orETM+.
TheoperatingdatesoftheLandsatsatellitesandtheinstrumentsonthemarelistedonTable1.
Launched
Retired
Instruments
Landsat-1(ERTS-1)
July23,1972
January,1978
RBV,MSS
Landsat-2
January22,1975
July,1983
Landsat-3
March5,1978
September,1983
Landsat-4
July16,1982
June,2001*
MSS,TM
Landsat-5
March1,1984
Landsat-6
October5,1993
ETM
Landsat-7
April15,1999
ETM+
Table1.LandsatSatellites,theirOperationalPeriods,andTheirInstruments.
*TheLandsat-4sensorswerenotoperationalafterJuly,1987;
thesatellitewaslaterusedformaneuvertesting.
ThedataontheseCD-ROMs,calledtheGeoCoverdataset,covertheUnitedStatesofAmerica,includingAlaskaandHawaii.
ThedatasetwasproducedbytheEarthSatelliteCorporationforNASAandcontainsapproximately900TMimages,orscenes.
EachLandsatsceneisabout115mileslongand115mileswide(or100nauticalmileslongand100nauticalmileswide,or185kilometerslongand185kilometerswide).
ThisdatasetcoverstheUnitedStatesaround1990andcamefromobservationsacquiredbytheLandsat-5satellite.
Becauseofsatelliteschedulingconstraintsandcloudcoverobscuringtheground,thescenesintheGeoCoverdatasetwerenotallobserved(acquired)onthesamedayorwithinthesamemonth,butincludescenesacquiredwithinayearortwoof1990.
Withineachimageorpicture,thesmallestpictureelement,orpixel,coversasquare28.5metersonaside.
Nomatterhowmuchyouzoominonanimage,thesmallestsquarethatyoucanseewillbe28.5metersonaside-evenifthereareonlyafewbigsquaresonyourscreen.
Thatdatasquareisabout94feetonaside,oranareaofaboutonefifthofanacreorabout0.08hectare.
TheTMpixelsizeenablesobservationoflargenaturalfeatures,suchasvolcanos,rivers,andforests,andlargeman-madefeatures.
Majorhighways,officebuildings(suchasthePentagonorUSCapitolbuilding),cityparksandagriculturalfields,airports,majorbridgesanddamsareapparent,butnarrowstreets,creeksandstreams,individualhouses,andautomobilescannotbediscerned.
Sincethedataarespreadover4CD-ROMs,theUnitedStateswasbrokenupintosmallerareascalledtilesormosaics.
CollectionsoftileswereputoneachCD-oneCD-ROMcoverstheeasternUnitedStates,anothercoversthecentralUnitedStates,athirdCD-ROMcoversthewesternUnitedStates,andonefinalCD-ROMcoversAlaskaandHawaii.
Eachtilecoversanareaof6degreesoflongitude(12degreesoflongitudeatlatitudesabovethan60degrees,affectingonlyAlaskandata)by5degreesoflatitude.
AdescriptionofthetilingschemecanbefoundintheGeoCoverProductDescriptionSheet(GeoCover.doc;
alsoAppendix3.).
Technicallyspeaking,thesedatawereorthorectified(geometricallycorrectedsothattheywouldappearastheywouldonamap,alwayslookingstraightdownandnotfromofftoaside).
Thenthedatawereprojected(displayed)usingtheUniversalTransverseMercatorprojectiontominimizethedistortioncausedbytakingapieceofasphereandflatteningit.
TheTMinstrumentonLandsat-5andtheETM+instrumentonLandsat-7observetheEarthwith7differentfiltersor"
bands"
.
Bands1,2,3,4,5,and7onbothinstrumentsaresensitivetolightenergyfromthesunreflectedbythesurfaceoftheEarth.
Eachbandissensitivetoadifferentpartofthereflectedsolarenergy.
Thepartsofthereflectedenergyaredefinedbythelengthofthelightwaves.
Thus,band1oftheTMandETM+instrumentsrecordsreflectedlightenergyonlyintherangeof0.45microns(µ
m-amicronisonemillionthofameterlong)to0.52µ
m.
Thehumaneyeseesreflectedlightinthatbandofwavelengthsasthecolorblue;
hence,band1issometimesreferredtoastheblueband.
Inasimilarmanner,bands2and3oftheTMandETM+instrumentsrecordreflectedgreenandredlight,respectively.
TMandETM+bands4,5,and7recordreflectedlightinwavelengthsthathumaneyescannotdetect.
Thesebandsarereferredtoasnearinfrared(NIR,band4)andshortwaveinfrared(SWIR,bands5and7).
Band6oftheTMandETM+instrumentsisdifferentfromalltheotherbandsbecauseitdoesnotrecordreflectedlightenergy,butratherheatenergyemittedbytheEarth'
Inadditiontothesebands,theETM+instrumentalsohasaneighthband,calledthepanchromaticsharpeningband.
ETM+band8issensitivetoreflectedlightenergyacrossabroadrangeofwavelengthsthatincludesblue,green,redandnearinfrared.
Thispanchromaticbandhasaspatialresolutionof15meters,ratherthanthe28.5or30metersofbands1,2,3,4,5and7.
ThesensitivitiesofMSS,TMandETM+bandsarelistedinTable2.
Band
RBV
MSS
TM
1
.48-.57µ
mgreen
.45-.52µ
mblue
2
.58-.68µ
mred
.52-.6µ
.53-.61µ
3
.69-.83µ
mIR
.63-.69µ
4
.5-.6µ
.76-.9µ
mNIR
.75-.9µ
5
.6-.7µ
1.55-1.75µ
mSWIR
6
0.7-0.8µ
10.4-12.5µ
mTIR
7
0.8-1.1µ
2.08-2.35µ
2.1-2.35µ
8
.52-.9µ
mpanchromatic
Table2.
LandsatInstrumentBands.IR=infrared;
NIR=nearinfrared;
SWIR=short
wavelengthinfrared;
TIR=thermalinfrared(longwavelength);
andµ
m=micronormicrometer.
Whatdothedifferentbandsmeantouswhenwelookatthedata?
Tofindoutwhateachindividualbandseesbest,orbetterthantheothers,checktheLandsat-7imagesshowninAppendix2.
Theindividualbandimagesappearasgrayscaleimages-likeold-fashionedblack-and-whitephotographs.
However,theycanbecombinedtoformcompositeimages,withadifferentgrayscaleimagefeedingadifferentcolorgun(typicallyared-green-blue,orRGBcombination).
Therearemanyband-colorcombinationsthattellusefulstories.
Threedifferentandoftenusedcompositesaresummarizedbelow.
______________________________________________________________________________
TrueColor:
Forthetruecolorrendition,band1isdisplayedinthebluecolor,band2isdisplayedinthegreencolor,andband3isdisplayedintheredcolor.
Theresultingimageisfairlyclosetorealistic-asthoughyoutookthepicturewithyourcameraandwereridinginthesatellite.
Butitisalsoprettydull-thereislittlecontrastandfeaturesintheimagearehardtodistinguish.
False-Color,alsocalledNearInfraredorNIR:
Inthisimage,band2isdisplayedinblue,band3isdisplayedingreen,andband4isdisplayedinred.
Thisrenditionlooksratherstrange-vegetationjumpsoutasabrightredbecausegreenvegetationreadilyreflectsinfraredlightenergy!
Itissimilartopicturestakenfromaircraftwhenusinginfraredfilmandisveryusefulforstudyingvegetation.
___________________________________________________________________________
Short-WavelengthInfrared,orSWIR:
InthisSWIRimage,band2isdisplayedinblue,band4isdisplayedingreen,andband7(or5)isdisplayedinred.
Thisrenditionlookslikeajazzeduptruecolorrendition-onewithmorestrikingcolors.
ThisisthebandcombinationwasusedintheGeoCoverdataset.
ItisbuiltintotheGeoCoverdataandcannotbechanged.
Further,thecontrastandbrightnesshavebeenalteredintheGeoCoverdatasettomakeamoreconsistentoverallmosaic.
TheappearanceofdifferentsurfacefeaturesforthedifferentcompositeimagesissummarizedonTable4.
TrueColor
Red:
Band3
Green:
Band2
Blue:
Band1
FalseColor
Band4
SWIR(GeoCover)
Band7
Treesandbushes
OliveGreen
Red
Shadesofgreen
Crops
Mediumtolig
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