实习一指导书.docx

实习一指导书.docx

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实习一指导书

Lab.01:

IntroductiontoENVI4.5（ENVI简介）

NotethatthereisaworksheetattheendofthisLabwrite-upthatyoumustturninattheendofthelabperiod.（实验后有一些问题，完成这些问题，并于实习结束后上交）

ENVIisapowerfulsoftwarepackagethatisarguablythemostcommonlyused（althoughtherearemanyothergoodpackages）byremotesensingscientistsformanipulatingandanalyzingdata.Inthisexerciseyouwillfamiliarizeyourselveswithitscapabilities.Probablythebestwaytogetstartedwithanycomplexsoftwareistoexplorethevariousmenusandbuttonstoseewhatkindsoftasksthesoftwarecando.

ENVIInstallation（安装）

Clickfile‘envi45winx86_32.exe’,afterfinishinstallingthisfile,copy“idl.dll”incracktodirector“C:

\ProgramFiles\ITT\IDL70\bin\bin.x86”,thancopyfolder“licence”todirector“C:

\ProgramFiles\ITT”

UsingENVIHelpDocuments（帮助文档）

Clickmenu:

Themostusefulforthisclassisaccessedbyclickingonthelittlequestionmark（?

）ontheupperrightsideoftheENVIinterface.

OpeningImages（打开影像）

1）StartENVI.

2）Let’sopenaLandsatThematicMapper（TM）imageinfolder“TM20080802”.Clickasthisfollowingfigureshow.

3）Inthisfolderisafoldercalled“SCENE01”,inthisfolder,choose“header.dat”andclickOK.Itshouldopen.

4）Openanimageingrayscale（灰度影像）.

Inthe“availablebandlists”,chooseanyoneband,click“grayscale”whichisadefaultoption,andclick“loadband”,thenthisimageisshowinginthreewindows,oneisforimage,oneisforscroll,oneisforzoom.

Nowlet’sopenasecondwindowsothatyoucandisplaytwoimagessidebyside.Chooseanotheroneband,andclick“NoDisplay”,choose“NewDisplay”,click“LoadBand”,thenthisimageisshowinginanotherthreewindows

5）openanimageinRGBColor（彩色影像）.

Chooseoption“RGBColor”whichisnexttooption“GrayScale”.ThenchooseonebandforchannelR,anotheronebandforChannelG,andanotheroneforChannelB,thenclick“loadband”

6）ChangingtheColorScheme（改变配色方案，即选择不同的波段分别赋给R、G、B三个通道，查看合成结果）

Theappearanceofanimagedependsonhowyouchoosetoassignthethreeadditiveprimarycolors（red,greenandblue）tosatelliteimagebands（alsocalledspectralbandsorchannels）.Theconventionistoassignwhicheverspectralbandcorrespondstonearinfrared（NIR）tothecolorred.

TheTMimagethatyouareusinghas7spectralbands,numbered1–7,eachofwhichhascapturedadifferentpartoftheelectromagneticspectrum.Nowyouwilltrytochangethebandsthatareassignedtotheprimarycolorstomaketheimagelooklikewhatyouwouldseewithyoureye（orwithaconventionalcamera）.Noticethattherearevariouscontrolsforchangingtheappearanceofimages.Experimentwithvariousbandcombinationswiththegoalofmakinganimagelooklikeitwouldlooktoyoureye.Notethatanystandingwaterwillbedark,vegetationwillbegreenish.Ontheworksheet,recordthebandtoprimarycolorcombinationsthatresultin“truecolor.”

GettingInformationaboutanImage（获取影像信息）

Oftenyouneedtogatherbasicinformationaboutimagefiles.First,someterminology:

“Raster”isthetechnicaltermforimageorGISdatathatarecomposedofpixelsarrangedinrows（orlinesorrecords）andcolumns（orsamples）.Eachx,y（row,column）gridcelliscalleda“pixel”（justlikeinyourdigitalcamera）.（栅格数据）

“Vector”isthetechnicaltermforGISpoint,line,andpolygondataincomputer（digital）format.Vectordataarecomposedofthex,ycoordinatesofpointsandinformationaboutifandhowthepointsareconnectedintolinesorareas（polygons）.（矢量数据）

AlayerinENVIiseitherasinglerastersatellitebandoravectordataset.（ENVI中图层可以是栅格也可以是矢量）

Afile（e.g.animagefile）canhaveoneorseverallayers.（一个影像文件中可有一个或多个图层）

Getthemapinformation:

Click⊕infrontof“mapinfo”in“availablebandlist”,thenyouwillseethemapinformationforthisimage.Readcarefullysothatyoucananswertheworksheetquestions.（获取地图信息）

RightClickontheLayerInfoiconatthetopofyour“availablebandlists”andchoose“EditHeader”.Awindowwillopenthatincludessomebasicinformationaboutthisfile,includingthenumberoflayers（bands）,thenumberofcolumns（width）androws（height）,thetypeofdata.（查看文件的基本信息）

RightClickontheLayerInfoiconatthetopofyour“availablebandlists”andchoose“QuickStats”.Afterafewminutes,awindowwillopenthatincludessomebasicinformationaboutthisfile,includingtheminimum,maximumandmeanpixelvaluesandotherinformationforeachband.Exploresomeofthetabsonthisinformationwindow（andanswertheworksheetquestions）.（查看文件的统计信息）

LinkingandUnlinkingImagesinSeparateGraphicsWindows（影像关联及解除影像关联）

Itisoftenusefulto“Link”viewerstogethersothatyoucanidentifythesamelocationintwoormoreimages.Gobacktoyour“Availablebandlist”,clicktwodifferentbandsonebyoneanddisplaythemintwodifferentwindows.Inanyoneimage,clickasthefollowingfigureshow:

（基于像素的关联）

Awindowdisplayedas:

ClickOK,thenthosetwoimageslinked.

ClickCursorlocations/valueasthefollowingfigureshow:

Ifyourimagesarelinked,redrectangleswillappearinbothimages（iftheyaren’tlinkedthewhitecrosswillonlyappearintheactiveimage）andawindowwillpopupthatcontainsinformationabouttheexactpixelattheintersectionoftherectangles.Movetherectanglearoundwithyourmouseandnotethatitmovesinbothimages.

Theabovemethodisalinkbasedonimagepixel.Pleasetrytolinktoimagebasedongeographicallocations.（基于地理位置的关联）

Worksheet:

Lab01:

IntroductionToENVI

（作业，要求每个题在必要的地方要截图，对结果仔细分析后回答问题）

1.Whataretherolesofthethreedifferentwindowsforoneimage?

（影像显示时，三个不同窗口的作用是什么？

）

2.Whatistheprojectionofthisimage?

whatisthepixelspatialresolution?

（给定影像的投影方式是什么？

空间分辨率是多少？

）

3.DescribetheTMimagethatyouoriginallyopenedusingthestandardfalsecolorcomposition（标准假彩色合成）（inanRGBimage,Band4（近红外波段）forchannelR（红通道）,Band3（红波段）forchannelG（绿通道）,Band2（绿波段）forchannelB）（蓝通道）.（影像的彩色合成）

a.Whatcoloristhevegetationsurroundingtown?

Why?

（城区外围植被是什么颜色，为什么？

）

b.Whatcoloristhewaterbody?

Why?

（水体是什么颜色，为什么？

）

4.DescribetheTMimagethatyouoriginallyopenedusinganotherfalsecolorcomposition（另一种假彩色合成）（inanRGBimage,Band5forchannelR,Band4forchannelG,Band3forchannelB）.（影像的彩色合成）

a.Whatcoloristhevegetationsurroundingtown?

Why?

（城区外围植被是什么颜色，为什么？

）

b.Whatcoloriswaterbody?

Why?

（水体是什么颜色，为什么？

）

5.Whatbandandcolorcombinationsarerequiredtomaketheimagelooklikewhatyoureyewouldsee（“truecolor”）?

（如何合成一景真彩色影像？

）

a.Whatcoloristhevegetationsurroundingtown?

Why?

（城区外围植被是什么颜色，为什么？

）

b.Whatcoloriswaterbody?

Why?

（水体是什么颜色，为什么？

）

c.Pleasemakeacomparisonofthevegetationcolor,waterbodycolorbasedontheresultsfromquestions3,4and5.（对3，4，5中植被、水体的颜色作一个对比.）

6.BasedontheLayerInformationwindowprovidethefollowinginformationabouttheTMimagefile:

（TM影像的相关信息）

a.Howmanybandsdoestheimagehave?

（影像有几个波段？

）

b.WhatisthemeanpixelvalueforBand4?

（第4个波段像素DN值的平均值是多少？

）

c.WhatistheminimumpixelvalueforBand2?

（第2个波段像素DN值的最小值是多少？

）

d.Whatisthehistogramforallbandslikeinthisimage?

（显示该影像所有波段的直方图。

）

7.Linkband2andband6basedongeographicallocations:

（基于地理位置对波段2和波段6进行关联）

a.WhataretheDNvaluesofwaterbodysurroundingforbiddencityinband2andband6?

（波段2和波段6中紫禁城外水体的DN值各是什么？

）

b.WhataretheDNvaluesofvegetationinTiantanParkinband2andband6?

（波段2和波段6中天坛公园植被的DN值各是什么？

）

Lab02:

ConvertingRadiancetoReflectance

（辐射率到反射率的转换）

Notethatthereisaworksheetattheendofthislabwrite-upthatyoumustturninattheendofthelabperiod.（实验后有一些问题，完成这些问题，并于是实习结束后上交）

TodaywewillusesomeENVItoolstoconvertwhatthesatellitemeasures,calledradiance,tothecharacteristicabilityofmaterialsonthegroundtoreflectlight（reflectance）.Therearemanyconceptsintoday’slabthatwehavediscussedinmuchmoredetailinthepastfewweeks,rememberingthatreflectanceisNOTdirectlymeasuredbysatellitesandmustinsteadbecalculated.

First,somedefinitions:

DigitalNumber（DN）–theunitlessintegerthatasatelliteusestorecordradiance（e.g.0–255where0=noradianceand255=somemaximumamountofradiancethatthesensorissensitiveto）.EachimagepixelhasoneDNforeachband.（DN值）

Radiance（L）–theamountoflightreceivedataparticularplace,inthiscaseasatellite（watts/m2/sr）.（辐射率）

Irradiance（E）–theamountofincominglightfromthesun（eitheratthegroundoratthetopoftheatmosphere（TOA）（watts/m2）.（入射辐射）

Reflectance（r）–theamountoflightthatreflectsoffofsomethingdividedbytheamountofincominglight（oftengivenasafractionorapercent）.（反射率）

Transmittance（t）–theproportionoflightthatistransmittedthroughsomething（e.g.,throughtheearth’satmosphere）,usuallygivenasafraction.（透过率）

Thefundamentaltaskinremotesensingisdistinguishingobjects（e.g.,plants,rocks）orproperties（e.g.,plantleafnutrientcontent）onearth,basedontheamountoflightthattheobjectsreflectacrossthevariouswavelengthsthatsatellitesmeasure（capturedinbands）.Theproblemisthatsatellitesdon’tmeasurereflectance,theymeasureradiance.Thepatternofradianceacrossthesatellitebandsisoftensimilartothepatternofreflectanceacrossthesamebands,butitisalteredbythingslikeatmosphericeffects.Anotherissueisthatweoftenneedtodirectlycomparethereflectanceofobjectsonthegroundwithreflectancecalculatedfromsatellitedata.Todothis,wemustconvertsatellitedigitalnumbers（DNs）orpi