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Principles of Remote Sensing

Principles of Remote Sensing . Image from NASA – Goddard Space Flight Center, NOAA GOES-8 satellite, 2 Sep ’94, 1800 UT. Scanning planet Earth from space. A hierarchy of remote sensing. Satellite sensing Aerial photography Ground-truthing.

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Principles of Remote Sensing

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  1. Principles of Remote Sensing Image from NASA – Goddard Space Flight Center, NOAA GOES-8 satellite, 2 Sep ’94, 1800 UT CS 128/ES 228 - Lecture 10b

  2. Scanning planet Earth from space CS 128/ES 228 - Lecture 10b

  3. A hierarchy of remote sensing • Satellite sensing • Aerial photography • Ground-truthing Image from Avery. Interpretation of Aerial Photographs. CS 128/ES 228 - Lecture 10b

  4. History of remote sensing • Earliest vehicle was …? • Tournachon (‘Nadar’) took 1st aerial photograph in 1858 (since lost) • Earliest conserved aerial photograph: Boston, J. Black, 1860 • Early applications were in military reconnaissance CS 128/ES 228 - Lecture 10b

  5. WWII – heavy use of aerial reconnaissance Images: Avery. 1977. Interpretation of Aerial Photographs. 3rd ed. Burgess Press, Minneapolis, MN. CS 128/ES 228 - Lecture 10b

  6. “Spy planes” & the Cold War CS 128/ES 228 - Lecture 10b

  7. Satellite sensing • Russian Sputnik (1957)- radio transmitter only • Rapid response by US:CORONA (1960) • Early applications: military reconnaissance CS 128/ES 228 - Lecture 10b

  8. Advantages of satellites • Wide coverage • Vertical (orthogonal) view at near-infinite height – photos are planimetric • Automated, 24/7 operation • Rapid data collection http://www.kidsgeo.com/geography-for-kids/0035-remote-sensing.php CS 128/ES 228 - Lecture 10b

  9. Spectral bands Three important spectral bands: • visible light • infrared radiation • microwave radiation Image from NASA 1987. SAR: Synthetic Aperture Radar. Earth Observing System, Vol. IIf. CS 128/ES 228 - Lecture 10b

  10. Passive vs. active sensing http://visual.merriam-webster.com/earth/geography/remote-sensing/satellite-remote-sensing.php CS 128/ES 228 - Lecture 10b

  11. Classes of sensors Photographic • panchromatic • color • Multi-spectral scanners • image scanned across sensors • sensors for many wavelengths • Infrared (IR) • film (near IR) • thermal IR sensors for longer wave-lengths • Radar • RAdio Detection And Ranging • active imaging CS 128/ES 228 - Lecture 10b

  12. Infrared sensors • IR penetrates haze and light cloud cover • can be used at night • used by military for camouflage detection • IR ‘signature’ often distinct from visible image CS 128/ES 228 - Lecture 10b

  13. Color IR film • Used with yellow (blue-absorbing) filter • 3 primary pigments, but not “true” (visible) color- green vegetation = red- clear water = dark blue- turbid water = bright blue- soil = green- urban areas = pale blue Top image: Committee on Earth Observation Satellites http://ceos.cnes.fr:8100/cdrom-98/ceos1/irsd/content.htm Bottom image: Avery. 1977. Interpretation of Aerial Photographs. 3rd ed. Burgess Press, Minneapolis, MN. CS 128/ES 228 - Lecture 10b

  14. Multispectral sensors • Visible + IR spectra • Multiple images, taken at difference wavelengths, in single pass Avery 1977. Interpretation of Aerial Photography. Burgess Publ., Ninneapolis CS 128/ES 228 - Lecture 10b

  15. Landsat Images • Landsat 1-4 launched 1972 – ’82; expired • Landsat 5 & 7 launched 1985 & 1999; both operational • TM: thematic mapper. - 7 spectral bands- designed primarily for ES themes http://landsat.gsfc.nasa.gov/project/L7images.html CS 128/ES 228 - Lecture 10b

  16. TM Applications CS 128/ES 228 - Lecture 10b

  17. Hydrology example Images from Avery. Interpretation of Aerial Photographs. CS 128/ES 228 - Lecture 10b

  18. Radar sensors • active sensing • day & night, all weather • less affected by scattering (aerosols) • vertical or oblique perspective Lo & Yeung, fig. 8.13 CS 128/ES 228 - Lecture 10b

  19. Uses of radar: altimetry • satellite-nadir distance • geoid & topographic measurements • sea elevation, tides & currents • wave/storm measurements Both images from NASA 1987. Altimetric System. Earth Observing System, Vol. IIh. CS 128/ES 228 - Lecture 10b

  20. Uses of radar: SAR • glaciology • hydrology • vegetation science • geology Image from NASA 1987. SAR: Synthetic Aperture Radar. Earth Observing System, Vol. IIf. CS 128/ES 228 - Lecture 10b

  21. Sensor resolution • Spatial: size of smallest objects visible on ground. Ranges from < 1m to > 1 km. Inversely related to area covered by image • Spectral: wavelengths recorded. Ex. panchromatic film (~0.2 – 0.7 µm); Landsat Thematic Mapper bands (0.06 to 0.24 µm wide) • Radiometric: # bits/pixel. Ex. Landsat TM (8 bit); AVRIS (12 bit) • Temporal: for satellite, time to repeat coverage. Ex. Landsats 5 & 7 (16 days) CS 128/ES 228 - Lecture 10b

  22. Spatial resolution of satellite images A sampler of recent (civilian) satellites: CS 128/ES 228 - Lecture 10b

  23. Satellite image resolution Quickbird 2 • Commercial venture • 0.63 m resolution • U.S. trying to discourage open access to finer resolution images Digitalglobe.com CS 128/ES 228 - Lecture 10b

  24. Satellite orbits Geostationary • 36,000 km above equator Polar • varying heights • often in Sun-synchronous orbits Both diagrams from European Organisation for the Exploitation of Meteorological Satellites www.eumetsat.de/en/mtp/space/polar.html CS 128/ES 228 - Lecture 10b

  25. Satellite coverage Geostationary • no polar coverage • coverage is 24/7 • low ground reso-lution (~ 1 km) Polar • global coverage • coverage is dis-continuous Both diagrams from European Organisation for the Exploitation of Meteorological Satellites www.eumetsat.de/en/mtp/space/polar.html CS 128/ES 228 - Lecture 10b

  26. Geostationary orbits Ex. GOES satellites • Meteorological satellites • GOES-8 at 75oW, GOES-9 at 135oW • 5 bands (1 visible, 4 thermal infrared) Image from NASA – Goddard Space Flight Center, NOAA GOES satellite, Hurricane Floyd, 15 Sep ‘99 CS 128/ES 228 - Lecture 10b

  27. Polar orbits Ex. Landsat & Terra satellites • 705 km height, ~100 minute orbit • 185 km swath • 16 day repeat • Sun-synchronousorbits (~0945 a.m. equator crossing) Orbit tracking data from NASA – http://liftoff.msfc.nasa.gov/realtime/JTrack/eos.html, 5 Mar ‘03 CS 128/ES 228 - Lecture 10b

  28. Terra (and EOS) • Terra launched 1999. Part of NASA’s Earth Observing System • Carries 5 instruments, including an MSS imager • 14 spectral bands Images from www.nasa.gov CS 128/ES 228 - Lecture 10b

  29. NYC drought The ASTER image pair depicts a 215-square-kilometer (80-square-mile) area around Ashokan Reservoir in the Catskill Mountains, one of several Catskills reservoirs that supply water to the New York City metropolitan area. The images, taken September 18, 2000, and February 3, 2002, show a dramatic decrease in reservoir water level to the current 52 percent of capacity. Image courtesy NASA/GSFC/MITI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team CS 128/ES 228 - Lecture 10b

  30. Urban development study Ulaanbaatar, Mongolia • Study used: • SPOT images • LANDSAT images • ASTER images • - 1:5,000 maps • - 1:10,000 aerial photos http://corp.mmp.kosnet.com/CORP_CD_2004/archiv/papers/CORP2004_RADNAABAZAR_KUFFER_HOFSTEE.PDF CS 128/ES 228 - Lecture 10b

  31. Ground truthing … … the fun part CS 128/ES 228 - Lecture 10b

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