遥感数字图像处理课件.ppt

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1、第四章遥感图像处理基本概念遥感数字图像处理预处理遥感数字图像处理之空间增强遥感数字图像处理之辐射增强遥感数字图像处理之波谱增强1.基本概念数字图像的定义：二维数组形式表示的图像数字图像基本数学特征：离散和有限数字图像处理算法类型：点处理和邻域处理数字图像处理的内容：恢复处理、增强处理、复合处理、分类处理理解栅格数据二维矩阵灰度图像理解数字图像处理理解数字图像处理2.遥感数字图像之预处理几何校正Thinkingabout:What?Why?How?裁切Thinkingabout:What?Why?How?镶嵌Thinkingabout:What?Why?Ho

2、w?几何校正-BasicConceptsRaw,remotelysensedimagedatagatheredbyasatellitearedistortedbyboththecurvatureoftheEarthandthesensorbeingusedmapprojectionsystemsalsocausesomedistortionRectificationistheprocessoftransformingthedatafromonegridsystemintoanothergridsystemusingageometrictransformat

3、ionRegistrationistheprocessofmakinganimageconformtoanotherimageGeoreferencingreferstotheprocessofassigningmapcoordinatestoimagedata.几何校正-WhentoRectifyRectificationisnecessaryincaseswherethepixelgridoftheimagemustbechangedtofitamapprojectionsystemorareferenceimage.Beforerectifyingt

4、hedata,youmustdeterminetheappropriatecoordinatesystemforthedatabase.Toselecttheoptimummapprojectionandcoordinatesystem,theprimaryuseforthedatabasemustbeconsidered.几何校正-WhentoGeoreferenceOnlyRectificationisnotnecessaryifthereisnodistortionintheimage.Forexample,ifanimagefileisproduc

5、edbyscanningordigitizingapapermapthatisinthedesiredprojectionsystem,thenthatimageisalreadyplanaranddoesnotrequirerectificationunlessthereissomeskeworrotationoftheimage.Scanninganddigitizingproduceimagesthatareplanar,butdonotcontainanymapcoordinateinformation.Theseimagesneedonlytob

6、egeoreferenced,whichisamuchsimplerprocessthanrectification.几何校正-DisadvantagesofRectificationDuringrectification,thedatafilevaluesofrectifiedpixelsmustberesampledtofitintoanewgridofpixelrowsandcolumns.Althoughsomeofthealgorithmsforcalculatingthesevaluesarehighlyreliable,somespectra

7、lintegrityofthedatacanbelostduringrectification.Anunrectifiedimageismorespectrallycorrectthanarectifiedimage.Thinkaboutthespectralsignatures几何校正-RectificationSteps1.LocateGCPs.GCPsarespecificpixelsinanimageforwhichtheoutputmapcoordinates(orotheroutputcoordinates)areknown2.Computea

8、ndtestatransformation.3.Createano