1、Remote Sensing 遥 感,Remote Sensing 遥感,Last LectureDefinitions of Remote SensingHistory of remote sensingTypes of aerial photographPhotogrammetryParallaxConclusions,Remote sensing involves collecting information about the Earth from a distance using electromagnetic sensorsIt evolved from aerial photog
2、raphyVertical stereopairs of aerial photographs are used to take 3-D measurements by measuring parallax,Remote Sensing 遥感,Sources of Energy,Sensing Systems,The remote sensing process,Transmission through atmosphere (down & up),Reflection of full spectrum,Signal relayed to earth,Satellite receiving s
3、tation,Data storage and archive,The remote sensing process,Data storage and archive,The remote sensing process,Sources of Energy,Sensing Systems,The remote sensing process,StructureThe electromagnetic spectrumVisible radiationWavelengths shorter than visible blueWavelengths longer than visible redAt
4、mospheric windowsSources of radiation used in remote sensingConclusions,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,StructureThe electromagnetic spectrumVisible radiationWavelengths shorter than visible blueWavelengths longer than visible redAtmospheric windowsSources of rad
5、iation used in remote sensingConclusions,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,The electromagnetic spectrum(电磁波谱） The range of wavelengths over which EMR is propagated Continuum between Gamma rays (3x10-9m) Radio waves (3x106m),Electromagnetic Radiation and the Electro
6、magnetic Spectrum（电磁波与电磁波谱）,The electromagnetic spectrum(电磁波谱） Main wavelengths used in remote sensingVisible to shortwave infrared (0.4-3.0 microns),Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,可见光到短波红外线,The electromagnetic spectrum(电磁波谱） Main wavelengths used in remote sens
7、ingVisible to shortwave infrared (0.4-3.0 microns)Thermal infrared (3.0-14.0 microns)（热红外线）,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,The electromagnetic spectrum(电磁波谱） Main wavelengths used in remote sensingVisible to shortwave infrared (0.4-3.0 microns)Thermal infrared (
8、3.0-14.0 microns)Microwaves 5-500 mm)微波,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,StructureThe electromagnetic spectrumVisible radiationWavelengths shorter than visible blueWavelengths longer than visible
9、 redAtmospheric windowsSources of radiation used in remote sensingConclusions,Visible radiation可见光辐射 The small part of the EM spectrum that can be detected by the human eyeBlue (0.4-0.5 microns)Green (0.5-0.6 microns)Red (0.6-0.7 microns),Electromagnetic Radiation and the Electromagnetic Spectrum（电磁
10、波与电磁波谱）,Visible radiation可见光辐射,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Visible radiation可见光辐射,True colour aerial photograph,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,StructureThe electromagnetic spectrumVisible radiationWavelengths shorter than
11、 visible blueWavelengths longer than visible redAtmospheric windowsSources of radiation used in remote sensingConclusions,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Beyond visible, EMR is not detectable by the human eye,Invisible,Invisible,Electromagnetic Radiation and the
12、Electromagnetic Spectrum（电磁波与电磁波谱）,Wavelengths shorter than visible blue 波长比蓝光短的辐射 Subdivided into:Ultaviolet（紫外线）X-raysGamma raysIntense atmospheric scattering at these wavelengths prohibits use in Earth surface remote sensing,Invisible,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波
13、与电磁波谱）,Wavelengths shorter than visible blue 波长比蓝光短的辐射with the exception of very low-level aerial gamma radiation surveys (c. 80m above ground level),Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Wavelengths shorter than visible blue 波长比蓝光短的辐射with the exception of very low-lev
14、el aerial gamma radiation surveys,Low-level airborne gamma radiation spectrometry, Nuclear Physics Institute, Rez, Czech Republic,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Wavelengths shorter than visible blue 波长比蓝光短的辐射 This atmospheric scattering is a good thing for us, s
15、ince these very short wavelengths are highly energeticPhoton energy = h fwhere h is Plancks constant （6.6310-34 Jsec） f = frequency (hertz),Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,StructureThe electromagnetic spectrumVisible radiationWavelengths shorter than visible blue
16、Wavelengths longer than visible redAtmospheric windowsSources of radiation used in remote sensingConclusions,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Wavelengths longer than visible red 波长比红光长的辐射 InfraredSubdivided intoNear infrared (NIR) 0.7 0.9 microns 近红外线,Electromagne
17、tic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Near infrared,False colour aerial photograph, using film sensitive to NIR radiation,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Wavelengths longer than visible red 波长比红光长的辐射 InfraredSubdivided intoNear infrared (NIR) 0
18、.7 0.9 micronsShortwave infrared (SWIR) 0.9 3.0 microns 短波红外线,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Shortwave infrared,False colour composite of Landsat Thematic Mapper SWIR data, Hundi anticline, Pakistan,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与
19、电磁波谱）,Wavelengths longer than visible red 波长比红光长的辐射 InfraredSubdivided intoNear infrared (NIR) 0.7 0.9 micronsShortwave infrared (SWIR) 0.9 3.0 micronsThermal infrared (TIR) 3 microns 1.4 mm 热红外线,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Thermal infrared,Thermal image show
20、ing heat loss from poorly insulated buildings,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Thermal infrared,TIMS image, Gold Butte Mountains, SW. USA,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Wavelengths longer than visible red 波长比红光长的辐射 Microwaves微
21、波All weather capability Requires antennas rather than optics,Microwaves,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Wavelengths longer than visible red 波长比红光长的辐射 Microwaves (passive)SSM/I images of sea ice Concentrations around Antarctica,Electromagnetic Radiation and the El
22、ectromagnetic Spectrum（电磁波与电磁波谱）,Wavelengths longer than visible redMicrowaves (active)Radarsat image of the Western part of the Ross Sea, Antarctica,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Wavelengths longer than visible redRadio wavesFixed installations for measuring s
23、ea stateMain remote sensing use is data transmission,Microwaves,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,StructureThe electromagnetic spectrumVisible radiationWavelengths shorter than visible blueWavelengths longer than visible redAtmospheric windowsSources of radiation u
24、sed in remote sensingConclusions,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Atmospheric windows（大气窗口） Atmospheric modification of EMR includes:Scattering（散射）Refraction（折射）Absorption（吸收） RAYLEIGH SCATTERING Caused by gases in upper atmosphereMolecules smaller than incident w
25、avelengthsWavelength dependent; intensity inversely proportional to 4th power of wavelength (blue light scattered c. four times as much as red light and UV light c. 16 times as much as red light)Causes the blue color of the sky,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Atm
26、ospheric windows Atmospheric modification of EMR includes:Scattering（散射）Refraction（折射）Absorption（吸收） MIE SCATTERINGTakes place in lower atmosphere (0-5km)Caused by aerosols (dust, pollen, smoke and water droplets)Particles have a diameter roughly equal to the incident wavelengthWavelength dependent;
27、 affects EMR mostly in the visible,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Atmospheric windows Atmospheric modification of EMR includes:Scattering（散射）Refraction（折射）Absorption（吸收） NON-SELECTIVE SCATTERINGTakes place in lower atmosphereParticles much larger than incident r
28、adiationNot wavelength dependentPrimary cause of haze,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Atmospheric windows Atmospheric modification of EMR includes:Scattering（散射）Refraction（折射）Absorption（吸收） GENERAL EFFECTS OF SCATTERINGSatellite images include atmospheric path ra
29、diance in addition to surface radianceDecreases spatial detail (fuzzy images)Reduces contrast,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Atmospheric windows Atmospheric modification of EMR includes:Scattering（散射）Refraction（折射）Absorption（吸收） REFRACTIONBending of lightOccurs
30、when light passes through two media with different density (atmospheric layers)Causes mirages during hot daysDegrades satellite images on hot, humid days,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Atmospheric windows Atmospheric modification of EMR includes:Scattering（散射）Re
31、fraction（折射）Absorption（吸收） ABSORPTION Mostly caused by three atmospheric gasesOZONE: absorbs UVCARBON DIOXIDE: Lower atmosphere, absorbs 13 - 17.5 micronsWATER VAPOUR: Lower atmosphere, absorbs between 5.5 and 7 microns and above 27 microns.,Electromagnetic Radiation and the Electromagnetic Spectrum
32、（电磁波与电磁波谱）,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Atmospheric windows（大气窗口）This all means that we cant use the whole range of the EMR spectrum for remote sensingThe atmosphere is only transparent enough at certain wavelengths (even here we lose c. 20%),Electromagnetic R
33、adiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Atmospheric windows,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Atmospheric windows,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,StructureThe electromagnetic spectrumVisible radiationWavelengths shor
34、ter than visible blueWavelengths longer than visible redAtmospheric windowsSources of radiation used in remote sensingConclusions,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Sources of radiation used in remote sensingNatural radiation(Passive)Reflected solar radiationEmitted
35、 terrestrial radiation cheap and easyArtificial radiation(Active)more controllable but requires a lot of power,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Natural radiation,Stefan-Boltzmanns Law M (T) = s T4 s = 5.6703 x 10-8 ( W/m2 K4 ) Relates radiance to the fourth power
36、of temperature (in K),Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Natural radiation,Planck Radiation Law,Gives shape of spectral curve,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Natural radiationWeins Displacement Law: As temperature increases, the
37、peak of the radiation curve moves to shorter wavelengths,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Natural radiation,Weins Displacement Law:m T = 2898 m KWhere m = wavelength of spectral peakT = temperature (K),Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波
38、与电磁波谱）,Natural radiationBecause the Sun is a lot hotter than the Earth, the two sources of radiation produce different spectral curves, defined by Stefan-Boltzmanns, Plancks and Weins LawsSun = Visible to SWIREarth = Thermal to microwaveSmall overlap around 3 microns,Electromagnetic Radiation and th
39、e Electromagnetic Spectrum（电磁波与电磁波谱）,Natural radiation,Solar,Terrestrial,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,Artificial radiationArtificial radiation is increasingly used in remote sensingLasers (visible radiation)Radar (microwave radiation),Electromagnetic Radiation
40、 and the Electromagnetic Spectrum（电磁波与电磁波谱）,StructureThe electromagnetic spectrumVisible radiationWavelengths shorter than visible blueWavelengths longer than visible redAtmospheric windowsSources of radiation used in remote sensingConclusions,Electromagnetic Radiation and the Electromagnetic Spectr
41、um（电磁波与电磁波谱）,ConclusionsRemote sensing makes use of visible-SWIR (reflected solar radiation), thermal (emitted terrestrial radiation) and microwaves (either emitted or artificially produced)Wavelengths limited to atmospheric windows,Electromagnetic Radiation and the Electromagnetic Spectrum（电磁波与电磁波谱）,The data transfer chain: 1,Solar radiation,Reflection of full spectrum,Transmission through atmosphere (down & up),Detection 4 bands (SPOT),空间信息采集（包括遥感平台和传感器） 地面接收和预处理（包括辐射校正和几何校正） 地面实况调查（如收集环境和气象数据） 信息分析应用系统,The remote sensing process,
