武大遥感概论英文课件Word文件下载.docx

武大遥感概论英文课件Word文件下载.docx

《武大遥感概论英文课件Word文件下载.docx》由会员分享，可在线阅读，更多相关《武大遥感概论英文课件Word文件下载.docx（38页珍藏版）》请在冰点文库上搜索。

Thescienceorartofobtainingreliablemeasurementsbymeansofphotographs.

In1980,theAmericanSocietyforPhotogrammetryandRemoteSensingexpandedthedefinitionofphotogrammetrytobe:

Theart,scienceandtechnologyofobtainingreliableinformationaboutphysicalobjectsandtheenvironmentthroughprocessesofrecording,measuring,andinterpretingphotographicimagesandpatternsofelectromagneticradiantenergyandotherphenomena.

Photogrammetryisfrequentlydividedintospecialtiesaccordingtothetypeofphotographsorimagesused,orthelocationfromwhichtheyweretaken.Instrumentationusingphotostakenfromthegroundsurfaceiscalledterrestrialphotogrammetry.Aerialorspacephotogrammetryconnotestheuseoftraditionalanalogphotographs（ASP,1960;

Colwell,1997）ordigitalphotographs（Light,1996,1999;

Hinz,1999）thathavebeentakenfromanyairborneorspaceborneplatforms,andthesemaybeeithervertical,orobliqueimages.ThegeometryandcharacteristicsofatypicalaerialphotographareshowninFigure1.1.Noticehowthenegativeisareversalinbothtoneandgeometryofthereal-worldobjectspace.Stereo-photogrammetrymeansthatoverlappingpairsofphotographyareobtainedandmeasured,orinterpretedinastereoscopicviewingdevice.Thisprovidesathree-dimensionalviewandcreatestheillusionthattheobserverisviewingareliefmodaloftheterrain.Stereo-photogrammmetryisessentialformeasuringthez-coordinateandthestereo-viewaidsininterpretationofthefeaturesresidingintheimagery.

Bothairborneandspacebornephotogrammetryembracetwobroadcategoriesofpractice.Thefirstistheclassicalcategory,inwhichquantitativemeasurementsaremade,andfromwhichgroundpositions,elevations,distances,areas,andvolumescanbecomputed,orfromwhichplanimetricandtopographicmapscanbedrawn.Thiscategoryisoftencalledprecisionormetricphotogrammetry.Themostcommonapplicationsofmetricphotogrammetryare:

·

Theproductionoftopographicmapsthatcontainisolines（contours）ofequalelevationabovedatum,andthehydrologyandtransportationnetwork;

TheextractionofDigitalElevationModels（DEM）thatcontaintheelevation,shape,size,andcoordinatesoftheterrainsurfaceinamatrixofequallyspacedx,y,z-coordinates;

Theextractionofplanimetricbuildinginfrastructureinformationincludingtheactualoutline（perimeterfootprint）ofbuildings,and

Thepreparationoforthophotoimagemapproductsthathavethemetricqualitiesofalinemapcoupledwiththeimagequalitiesofanaerialphotograph.

Thesecondcategoryiscalledinterpretationinwhichphotographsareevaluatedinaqualitativemannerinordertoevaluatetimberstands,detectwaterpollution,classifysoils,interpretgeologicalformations,identifycrops,obtainmilitaryintelligence,etc.（Colwell1984）.Photointerpretationcoupledwithfundamentalphotogrammetricanalysisoftenresultsinthecreationofthethematicmapsof:

Landuse（categoriesdescribingthehumanuseoftheland,e.g.,recreation）;

Landcover（categoriesdescribingtheactualgroundsurfacecover,e.g.,forest）;

and/or

Biophsicalinformationsuchastheidentificationofareasofpotentialstressinacolor-infraredphotographofanagriculturalfield.

Sinceabout1940,photogrammetristshavetransitionedfromprojectioninstruments,analogueandanalyticalplotters（computerassistedplotters）,tosoft-copy,computerdrivenworkstations（Helava,1988）.Today,mostphotogrammetryproblemsareprocessedusingPersonalComputers（PCs）withsoftwarethathandlesphotogrammetricproblemsusingpurelymathematicalmethods（Leberl,1994;

Roberts,1996）.Theever-growingpowerofcomputerssincethe1950shasfavoredthedevelopmentofso-called‘analyticalphotogrammetry’.Inanalyticalphotogrammetry,asdistinguishedfrominstrumental,amathematicalmodelisconstructedorepresentthegeometricrelationsbetweenpointsintheobjectspace,theperspectivecenterinthelens,andtheimagepointsintheimageryorphotographs.Thesethreepointsfallonastraightline.Theyaresaidtobeco-linear,givingrisetothecolinearityconditionsformodernanalyticalphotogrammetry.Thecomputer’sapplicationofnumericalanalysistothismath-modelresultsinthesolutionofproblemsforcameracalibration,spaceintersection,andtriangulationofgroups,strips,ofblocksofaerial,spaceofterrestrialphotographs（WolfandDewitt,2000）.

Figure1.1Mostaerialphotographyisobtainedusingaircraft.Thisillustrationdepictsthegeometryandcoordinatecharacteristicsofa1:

6,000-scaleverticalaerialphotographofdowntownColumbia,SCshowninperspective.Thenegativeisareversalofboththetoneandgeometryofthereal-worldwhilethepositiveprintmaintainsthesamegeometryandtonalcharacteristicsasthereal-world（afterJensen,2000）.

1.2.1Airbornereconnaissancesystems

Thenumberofairbornereconnaissancesystemsinoperationissubstantiallygreaterthanthenumberofsatellitesystems.Airbornesystemscanalsooperateoverabroadrangeoftheelectromagneticspectrum.Theycanchangealtitudeandsensors,whereasatellitesystemisfixedonceinorbit.Airbornesensorsgenerallyachievehigherspatialresolution,manyatthesub-meterlevel.Airbornereconnaissanceplatformscanvarytheiraltitude,flyunderhighcloudsandwithchangingprioritiesareeasilyre-locatable.CharacteristicsofbothairborneandsatellitesystemsarecharacterizedinTable1.1.

Table1.1Airborneversussatellitereconnaissancedatacollectioncharacteristics

Characteristics

Airborne

Satellite

1.2.1Altitude

1.2.2Lowto30,000m

1.2.3175-1000km

Swatchwidth

Narrow（manystrips）

Usuallywide（largeareas）

Resolution

Canbevariedtomeetneeds

Fixedbysatelliteorbit（exceptforradar）

Illumination

Variablenon-sun-synchronous

Usuallysun-synchronous

Revisit

Frequentandflexible

Fixedbyorbit-days,unlessithasanoff-nadirpointingcapability

Geographicresponsiveness

Re-locatable

Fixedbyorbit-days

Flightpath

Variable,user-defined

Fixedbyorbit

Access

Intrusive

Non-intrusive

Airbornemilitaryphoto-reconnaissanceusuallymeansaircraftthatcanflyhigh（>

30,000ftaboveground）andfast（>

420knots）toobtainreconnaissanceimageryinashorttimeoverthetarget,preferablyundetected.Photo-reconnaissanceformonitoringforestfires,floodsandnaturaldisasterscanutilizeordinaryaircraft.Militaryphoto-reconnaissancegenerallyreliesonfastaircraftandlongfocallengthfilmordigitalcameras.SomeoftheUSaircraftusedinaerialreconnaissanceovertheyearsaresummarizedinTable1.2

1.3Remotesensing

Thetermremotesensingwasfirstintroducedintheearly1960sbythestaffoftheGeographyBranchoftheOfficeofNavalResearch（ONR）（Pruitt1979;

Jensen2000）.AerialphotointerpretationhadbecomeveryimportantinWorldWarII.TheSpaceagewasjustgettingunderwaywiththe1947launchofSputnik（USSR）,the1958launchofExplorer1（US）,andthecollectionofphotographyfromthethensecretCORONAprograminitiatedin1960.TheGeographyBranchofONRwasexpandingitsresearchusinginstrumentsotherthancameras（e.g.scanners,radiometers）andintoregionsoftheelectromagneticspectrumbeyondthevisibleandnear-infraredregions（e.g.,thermalinfrared,microwave）.Inthelate1950sitbecameapparentthattheprefix‘photo’wasbeingstretchedtoofarinviewofthefactthattherootword,photography,literallymeans‘towritewith（visible）light’（Colwell1997）.Pruitt（1979）wrote:

ThewholefieldwasinfluxanditwasdifficultfortheGeographyProgramtoknowwhichwaytomove.Itwasfinallydecidedin1960totaketheproblemtotheAdvisoryCommittee.WalterH.BaileyandIponderedalongtimeonhowtopresentthesituationandonwhattocallthebroaderfieldthatwefeltshouldbeencompassedinaprogramtoreplacetheaerialphotointerpretationproject.Theterm‘photograph’wastolimitedbecauseitdidnotcovertheregionsintheelectromagneticspectrumbeyondthe‘visible’range,anditwasinthesenon-visiblefrequenciesthatthefutureofinterpretationseemedtolie.‘Aerial’wasalsotoolimitedinviewofthepotentialforseeingtheEarthfromspace.

Basedonthesediscussion,thetermremotesensingwaspromotedinaseriesofsymposiasponsoredbyONRattheWillowRunLaboratoriesoftheUniversityofMichiganinconjunctionwiththeNationalResearchCouncilt