REMOTE SENSING INTERPRETATION Jan Clevers Centre for Geo-Information - WU Remote Sensing --> RS Sensor at a distance EARTH OBSERVATION EM energy Earth RS is a tool; one of the sources of information! 1
GIS Geographical Information System Well-considered combination of mutually referring data sets of various kinds of positionbound thematic data (database), software inclusive Requirement: the information layers match geometrically ==> OVERLAY STRUCTURE GIS file: 1. topography 2. soils 3. geology 4. precipitation 5. land cover 6. vegetation 7. remote sensing data 8. surface temperature 9. hydrology 10. population 11. nature conservation 12. environment 13. digital terrain model 14. topographical map 15. ------------------- 16. ------------------- 17. ------------------- field data (point measurements) vector data raster data Meteosat: meteorological satellite 2
Meteosat image of Europe Wageningen, Thematic Mapper Band 4 5 3 3
Rotterdam harbour, daytime Rotterdam harbour, nighttime 4
The remote sensing system A = source B = atmosphere C = object D = sensor E = reception F = data analysis G = final product Source of EM radiation 10 0 radiation (Wcm -2 µm -1 ) 10-1 curves for an average object on Earth 10-2 10-3 reflected solar radiation emitted thermal radiation 10-4 0.2 0.5 1.0 2 5 10 20 wavelength (µm) REFLECTION EMISSION 5
EM Spectrum and Windows reflection emission blue green red 0.3 0.6 1.0 5.0 10 50 100 200 µm 1mm 1cm 1m 10m 100 atmospheric transmittance 0 UV VIS NIR photography MIR MIR TIR human eye lidar TIR thermal scanners blocking effect of atmosphere microwaves radar multispectral scanners microwave radiometry 0.3 0.6 1.0 5.0 10 50 100 200 µm 1mm 1cm 1m 10m wavelength optical window microwave window Active <-> Passive RS using reflected solar radiation: (PASSIVE) RS using radiation emitted by objects: (PASSIVE) ACTIVE RS: 6
Principles imaging sensor systems analogue recording digital recording digital recording aerial image plane shutter scanning mirror imaging optics line array detector imaging optics point detector imaging optics Camera (aerial photography) Whiskbroom scanner Pushbroom scanner The position of the spectral bands of some Remote Sensing sensor systems in the optical window Meteosat NOAA AVHRR Landsat TM SPOT HRG multispectral SPOT HRG Panchromatic Pan: IKONOS, Quickbird, GeoEye, WorldView Multispectral: IKONOS, Quickbird, GeoEye, WorldView 60 reflectance (%) dry soil 40 infrared infrared 20 wet soil water vegetation 0 0.4 0.8 1.2 1.6 2.0 near- middle- 2.4 λ wavelength (µm) blue green red 7
Image Processing Options Tape/DVD/CD: Screen: latent image Visualization picture 1 picture 2 ------- ------- picture n Options: e.g. spectral band selection filtering displaying band composites band ratioing contrast modification vegetation index computation histogram equalization classification grey scale enhancement texture analysis colour assignment segmentation density slicing geometric correction principal components transformation Example TM-image, band 4-3-2 (R,G,B) 8
RS Properties Synopsis overview region differences and coherence Flexibility Actuality Interactivity Dynamics Moreover: variety of sensors, techniques, processing algorithms reproducible analysis in addition to conventional mapping specified data for application up to date information co-operation of human knowledge and machine operations capability of monitoring with time series of data reveals changes (change detection) the invisible becomes visible objective and quantitative data extrapolation of point measurements open up inaccessible regions integration with GIS MERIS image of Europe 9
Satellite based land cover classification Dutch land cover data base LGN5 10
LGN5 detail The Hague - Rotterdam Global land cover classification - MODIS Land Cover Fill Value Water Evergreen Needleleaf Forest Evergreen Broadleaf Forest Deciduous Needleleaf Forest Deciduous Broadleaf Forest Mixed Forest Closed Shrubland Open Shrubland Woody Savannas Savannas Grasslands Permanent Wetlands Croplands Urban and Built-Up Cropland/Natural Vegetation Mosaic Snow and Ice Barren or Sparsely Vegetated Unclassified Class 255 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 254 Color 11
Primary Productivity - June 2005 Primary Productivity December 2004 12
Perspective view of the Aletsch glacier (CH) Remote Sensing Interpretation 2) Spectral signatures 3) Aerial Photography 4) Multispectral Scanning 5) Microwave Remote Sensing 6) Digital Image Processing See: www.geo informatie.nl/courses/gima_rs Wageningen UR 2010 13