... LLCSyntheticApertureRadar Algorithms ClayStewartScienceApplicationsInternationalCorporationVicLarsonScienceApplicationsInternationalCorporation 33. 1Introduction 33. 2ImageFormationSide-LookingAirborneRadar(SLAR)•UnfocusedSyntheticApertureRadar•FocusedSyntheticApertureRadar 33. 3SARImageEnhancement 33. 4AutomaticObjectDetectionandClassificationinSARImageryReferencesFurtherReadingandOpenResearchIssues 33. 1 ... of a synthetic array antenna to increase the cross-range resolution. 33. 2.2 Unfocused Synthetic Aperture Radar Figure 33. 1 provides a good geometric description of SAR. As with SLAR, the radar ... LLCSyntheticApertureRadar Algorithms ClayStewartScienceApplicationsInternationalCorporationVicLarsonScienceApplicationsInternationalCorporation 33. 1Introduction 33. 2ImageFormationSide-LookingAirborneRadar(SLAR)•UnfocusedSyntheticApertureRadar•FocusedSyntheticApertureRadar 33. 3SARImageEnhancement 33. 4AutomaticObjectDetectionandClassificationinSARImageryReferencesFurtherReadingandOpenResearchIssues 33. 1 IntroductionAsyntheticapertureradar(SAR)isaradarsensorthatprovidesazimuthresolutionsuperiortothatachievablewithitsrealbeambysynthesizingalongapertureusingplatformmotion.ThegeometryfortheproductionoftheSARimageisshowninFig .33. 1.TheSARisusedtogenerateanelectromagneticmapofthesurfaceoftheearthfromanairborneorspaceborneplatform.Thiselectromagneticmapofthesurfacecontainsinformationthatcanbeusedtodistinguishdifferenttypesofobjectsthatmakeupthesurface.Thesensoriscalledasyntheticapertureradarbecauseasyntheticapertureisusedtoachievethenarrowbeamwidthnecessarytogetahighcross-rangeresolution.InSARimagerythetwodimensionsarerange(perpendiculartothesensor)andcross-range(paralleltothesensor).Therangeresolutionisachievedusingahighbandwidthpulsedwaveform.Thecross-rangeresolutionisachievedbymakinguseoftheforwardmotionoftheradarplatformtosynthesizealongaperturegivinganarrowbeamwidthandhighcross-rangeresolution.Thepulsereturnscollectedalongthissyntheticaperturearecoherentlycombinedtocreatethehighcross-rangeresolutionimage.ASARsensorisadvantageouscomparedtoanopticalsensorbecauseitcanoperatedayandnightthroughclouds,fog,andrain,aswellasatverylongranges.Atverylownominaloperatingfrequencies,lessthan1GHz,theradarevenpenetratesfoliageandcanimageobjectsbelowthetreecanopy.TheresolutionofaSARgroundmapisalsonotfundamentallylimitedbytherangefromthesensortotheground.Ifagivenresolutionisdesiredatalongerrange,thesyntheticaperturecansimplybemadelongertoachievethedesiredcross-rangeresolution.ASARimagemaycontain“speckle”orcoherentnoisebecauseitresultsfromcoherentprocessingofthedata.ThisspecklenoiseisacommoncharacteristicofhighfrequencySARimageryandreducingspeckle,orbuildingalgorithmsthatminimizespeckle,isamajorpartofprocessingSARimagerybeyondtheimageformationstage.Traditionaltechniquesaveragedtheintensityofadjacentpixels,resultinginasmootherbutlowerresolutionimage.AdvancedSARsensorscancollectmultiplepolarimetricand/orfrequencychannelswhereeachchannelcontainsuniqueinformationaboutthec1999byCRCPressLLCFIGURE...