Introduction to remote sensing: Content (1/2) Definition: photogrammetry and remote sensing (PRS) Radiation sources: solar radiation (passive optical RS) earth emission (passive microwave or thermal infrared RS) sensor (active RS; laser, microwaves) Electromagnetic spectrum: visible, infrared, thermal infrared, microwaves Interactions of radiation with: atmosphere: refraction, scattering, absorption, reflection, transmission earth / object surface: reflectance (microwaves: backscatter), specular refl./backsc., diffuse refl. / backsc., transmission, absorption, emission sensor system: radiometric (intensity of information), geometric (location of information) Spectral response of earth surface: reflectance curves, transmission of earth s atmosphere, spectral bands Sensor platforms: spaceborne, airborne, terrestrial / ground Sensor types: analogue photography (, digitised analogue photography) digital optical imaging: optical scanner, CCD camera, linear array CCD sensor (pushbroom) synthetic aperture RADAR (SAR) laserscanning (LIDAR) RADAR or LIDAR altimeter Digital image Resolution in RS: spatial, temporal, spectral, radiometric Colour, colour systems, colour composites (true, false) Introduction to remote sensing What kind of geoscientific tasks can be solved by remote sensing? What are the remote sensing principles behind these solutions? Introduction to remote sensing: Content (2/2) Filtering: local / global, high / low frequencies Image corrections: radiometric corrections: sensor, atmosphere, topography geometric corrections: co-registration, geo-referencing, ortho-projection Multispectral image classification Generation of digital elevation models (DEM): stereo images interferometric SAR (InSAR) altimeters laserscanning Measurement of displacements image correlation differential InSAR (DInSAR) Example studies Definition Photogrammetry and Remote Sensing is the art, science, and technology of obtaining reliable information from non-contact imaging and other sensor systems about the Earth and its environment, and other physical objects and processes through recording, measuring, analyzing and representation. (ISPRS)
Radiation sources (passive optical remote sensing) Sun Terrain / object surface Ellesmere Island from ASTER 5 km Sensor Image composite from MODIS Swiss Alps from ASTER
Radiation sources (passive microwave or thermal remote sensing) Sensor Terrain / object surface Tordrillo mountains from Landsat/ASTER 1 km Sea ice concentration from SSMI 2003 Tordrillo mountains, Landsat day-time thermal NASA 1 km
Tordrillo mountains, ASTER night-time thermal Radiation sources (active remote sensing, e.g. microwave, laser) Separate radiation source Sensor 1 km Terrain / object surface Synthetic aperture radar (SAR) from ASAR Hurricane Katrina from SAR (left) and optical sensor (right)
Laserscanning (light detection and ranging, LIDAR) SWIR: short-wave infrared MIR: middle infrared TIR: thermal infrared Optical to microwave spectrum UV: ultraviolet VIS: visible NIR: near infrared VNIR: visible and near infrared Geist et al. 2003 Electromagnetic spectrum Q: photon energy, h: Planck s constant, c: speed of light Radiation interaction with the atmosphere Atmosphere: refraction scattering absorption reflectance transmission c=λ f Q = (h c) / λ Atmosphere: refraction scattering absorption reflectance transmission
Radiation interaction with the terrain / object Radiation interaction with the sensor Surface: reflectance / backscatter (microwaves) specular reflectance / backscatter (microwaves) diffuse reflectance / backscatter (microwaves) transmission absorption emission Typical reflection curves for snow, vegetation and bare ground Tordrillo mountains from Landsat/ASTER Sensor: radiometric interactions geometric interactions 1 km
Landsat ETM 2, green Landsat ETM 3, red Landsat ETM 4, near infrared Landsat ETM 5, short-wave infrared
Landsat ETM 6, thermal infrared Sensor types Platform: terrestrial / ground airborne spaceborne Sensor types Sensor types (optical) Analogue: Analogue photographs Passive optical Laserscanning (LIDAR) Digital: (digitized analogue photographs) optical scanner CCD array linear CCD array, pushbroom Altimeter, microwave (RADAR) or laser (LIDAR) Microwave, active (SAR) Sensor
Black & white aerial image Colour aerial image Infrared aerial image
Optical scanner Linear array CCD sensor, pushbroom Japan Association of Remote Sensing CCD array sensor CCD array Ground / object Lens system Linear array CCD sensor, pushbroom
Landsat ETM 4, near infrared Landsat ETM 4, near infrared Digital image, pixels Resolution 11 21 34 34 32 97 78 66 68 54 spatial resolution 77 113 120 132 31 255 203 176 123 62 243 216 232 154 141 temporal resolution spectral resolution radiometric resolution 8 bit = 2 8 = 256 grey levels 16 bit = 2 16 = 65536 grey levels
Spatial resolution Meteosat, 5 km spatial resolution s c S / s = H / c H S MERIS, 300 m spatial resolution Quickbird, 0.6 m spatial resolution
Resolution spatial resolution temporal resolution (in parts coupled to spatial resolution; hours, days, weeks, months) spectral resolution radiometric resolution Resolution spatial resolution temporal resolution spectral resolution radiometric resolution 8 bit = 2 8 = 256 grey levels 16 bit = 2 16 = 65536 grey levels Spectral resolution Bandwidth Location of bands Colour systems
Colour systems True colour / false colour composites Red Green Blue Cyan Yellow Magenta Intensity Hue Saturation True colour / false colour composites True colour / false colour composites
Image filtering Types of filters: Local (constructed on base of a image section) Global (constructed on base of the entire image section) Landsat ETM 4, near infrared High image frequencies Low image frequencies 1 km Local, low (frequency) pass filters 250 250 250 100 250 3 x 3 medium 250 250 250 100 250 3 x 3 median Gaussian 3 x 3 low pass filter 250 250 233 233 233 250 250 233 233 233 250 250 233 233 233 1 km
3 x 3 high pass filter Ortho-projection (-rectification) 4 km Only geo-referenced 1 km Image corrections Radiometric corrections (pixel value): sensor correction, and atmospheric correction, and topographic correction (illumination bias due to terrain slope and aspect) Geometric corrections (pixel location) co-registration, or geo-referencing, or ortho-projection (also called ortho-rectification) Classification
Classification Generation of digital elevation models (DEM) SWIR 255 stereo imagery Red interferometric synthetic aperture radar altimetry laserscanning 255 Red SWIR Airborne stereo photogrammetry Airborne stereo photogrammetry
Satellite stereo Satellite stereo Satellite image draped over DEM from satellite stereo Interferometric synthetic aperture radar (InSAR) Tasman glacier, NZ Mt. Cook 25 Back looking: ASTER 3B
DEM from interferometric synthetic aperture radar (InSAR) RADAR / LIDAR altimetry ESA ERS / B. Alsdorf J. Bamber et al. 2000 Laserscanning (LIDAR) Surface displacement measurements from repeat images 1990
Surface displacement measurements from repeat images Surface displacement measurements from differential interferometric synthetic aperture radar (DInSAR) Interferometric synthetic aperture radar (DInSAR) Significance of remote sensing global observation coverage of large areas at once no ground-access needed none-visible terrain / object properties