测绘专业英语翻译31单元

Unit31InterferometricSAR(InSAR)Introduction干涉雷达(SAR)介绍Radarinterferometryisatechniqueforextractingthree-dimensionalinformationoftheEarth’ssurfacebyusingthephasecontentofradarsignalasanadditionalinformationsourcederivedfromthecomplexradardata.ItwasfirstusedinobservationofthesurfaceofVenusandtheMoon.雷达干涉测量技术中提取三维信息的地球表面的利用雷达信号的相位内容作为额外的信息源来自复杂的雷达数据。它最初是用于观察金星和月亮的表面GrahamwasthefirsttointroduceSyntheticApertureRadar(SAR)fortopographicmappingin1974.Therearetwokindsofinformationwhicharerequiredfortheproductionoftopographicmaps.Firstly,thevariousobjectsandfeaturestobemappedmustbepresentedinanimagewithsufficientresolutiontobeidentified.Secondly,athree_dimensionalmeasurementofposition,withrespecttotheplatform,ofasufficientnumberofpointsmustbemadetodefinetheterrainsurface.Thethree_dimensionalmeasurementcanbemadebySARinterferometrywithaside_lookinggeometryfrombothairborneandspaceborneSARsensors.格雷厄姆是第一个介绍合成孔径雷达(SAR)在1974年地形映射。有两种类型的信息所需的地形图的生产。首先,各种对象和特征映射必须以足够的分辨率的图像。其次,一个三维位置测量,对平台,足够数量的点必须定义地形表面。三维测量可以通过侧视SAR干涉测量几何机载和星载SAR传感器。ASyntheticApertureRadarisanactivesensortransmittingandreceivingmicrowavesignals,i.e.MeasuringdistancesbetweenthesensorandthepointontheEarth’ssurface,wherethesignalisbackscattered.Thesensoremitselectromagneticradiation(EMR)andthenrecordsthestrengthandtimedelayofthereturningsignaltoproduceimagesoftheground.TheEMRinvolvedcanbeimaginedasasinewave.ConventionalSARimagesaremadeup(asaraster)oftheamplitudeor‘strength’ofthesinewave—showninimagesasgreylevelintensityvalues.Whenthesinewavestartstorepeatitself(phaseangle360degrees),onecycleofphasehasoccurred.Ifwecollecttwoseparateimagesfromexactlythesamesatelliteposition(samerange),butatdifferenttimeswithnothinginthetargetareachanging,onewouldexpectthetwosinewavesfromeachimagetobethesameandinphasewitheachother.合成孔径雷达是一个活跃的传感器传送和接收微波信号,我即。测量传感器之间的距离和地球表面上的点,背散射信号。传感器发出的电磁辐射(EMR),然后记录返回信号的强度和时间延迟产生的地面图像。涉及的EMR可以想象为一个正弦波。传统的SAR图像是由(光栅)的振幅或强度相近正弦波-所示图像灰度级强度值当正弦波开始重演(相位角360度),一个周期的阶段发生。如果我们收集两个单独的图片完全相同的卫星位置相同(范围),但在不同的时间与目标区域中没有改变,人会期望每个图像的两个正弦波是相同的,彼此在阶段。Inpractice,thepositionofthesatellitebetweentwoimageacquisitionsisneveridentical,andthecorrespondingdifferenceinthepath(distancebetweensatelliteandground)meansthereisadifferenceinphasebetweenthetwosignals—aphaseshift.Thephysicalpathdifferencecanbeexpressedasanintegernumberofwavelengthsplusthefractionofonewavelength.Itcanalsobeexpressedasadifferenceinphaseanglebetweenthetwosignals.SARinterferometrymakesuseofthisphaseinformationbysubtractingthephasevalueinoneimagefromthatoftheother,forthesamepointontheground.Thisis,ineffect,generatingtheinterferencebetweenthetwophasessignalsandisthebasisofinterferometry.Fortheinterferometricprocesstoworksuccessfully,adegreeofsimilarity,orcorrelationmustexistinthesurfacepropertiesbetweenthetwoimageacquisitions.Inmostpartsoftheworld,particularlytemperateregions,correlationbetweenimageswilldegradewithtimeduetochanging/movingvegetation,differingclimaticconditions—termed’temporaldecorrelation’.Correlationtendstoremaingoodinarid,desertregionswherelittlechangeoccurs.Anoutputfromtheprocessingchainisacoherenceimage,andthisrepresentsthecorrelationthatexistsbetweencorrespondingpixelsofthetwoimages—lighterpixelsshowinggoodcorrelation(e.g.arid,drylandcover),anddarkerpixelsshowingbadcorrelation(e.g.water,changingvegetation).在实践中,卫星的位置两个图像之间的收购不相同,和相应的不同路径(卫星和地面之间的距离)意味着不同的两个信号之间的相位相移。物理路径的不同可以表示为一个整数的波长数量+一个波长的一部分。它也可以表示为一个两个信号之间的相角差。SAR干涉测量法利用这个阶段信息阶段价值减去另一个图像的同一点在地上。实际上,这是产生两个阶段之间的干扰信号和干涉,干涉的基础过程成功地工作,一定程度的相似性,或相关性必须存在于表面性质两个图像之间的收购。在世界的大部分地区,特别是温带地区,图像之间的相关性会随着时间降低由于改变/移动的植被,不同的气候条件,称为“时间解相关”。相关倾向于保持在干旱,沙漠地区发生微小的变化。处理链的输出是一个连贯性的形象,这代表了相应的像素之间的相关性存在两个图像——轻像素显示良好的相关性(e.g。干旱、干燥的土地覆盖),和较暗的像素显示坏相关性(e.g。水、植被变化)。Thephasevalueorangle(andhencephasedifferencesinaninterferogram)isnotknownabsolutely,butisgivenintherange0-360degrees,i.e.thephaseiswrappedontoafixedrangeofangleof0-360degrees.InordertocomputeterrainheightsandgenerateaDEM,theinterferogramfringeshavetobeunwrapped,i.e.thecorrectmultipleof360degreesmustbeaddedtothephasedifferenceateachpixel,theproblemofsolvingthis2πambiguityiscalledphaseunwrapping.Ifthegroundwereflat,unwrappingtheaboveinterferogramwouldproduceanimageofconstantgreylevel.相位值或角(因此在干涉图相位差异)绝对是未知的,但范围在0-360度,我即。阶段包装到一个固定的角度范围0-360度。为了计算地形高度和生成DEM,干涉图的边缘必须打开,我生产。正确的360度必须添加到多个相位差在每个像素,解决这一问题的2π模棱两可称为相位展开。如果地面是平的,打开上面的干涉图会产生恒定的灰度级的图像。在世界的大部分地区,特别是温带地区,图像之间的相关性会随着时间降低由于改变/移动的植被,不同的气候条件,称为“时间解相关”。Theinterferometricdataprocessingschemeincludesingeneral(1)registrationofthecompleximages,(2)theformationoftheinterferograms,(3)thephaseunwrapping,and(4)thedigitalelevationmodelreconstruction.干涉数据处理方案一般包括(1)登记的复杂图像,(2)干涉图的形成,相位(3),(4)数字高程模型重建。ThebasicuseofSARinterferometryistoestimatetopographicheight.However,advancementonthistechniquecanveryusefullybeappliedtomapsurfacedisplacementssuchasthoseassociatedwithearthquakes,landsliporsubsidence.Knownasdifferentialinterferometry,themethodusesSARimagesofdifferentdatesthatmightspanasurfacedisplacementevent.Afirstinterferogramiscreatedrepresentingtopo