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ESM 266: Multispectral remote sensing

2. Radiation and remote sensing. For example, if energy being sensed comes from the Sun, it:is radiated by atomic particles at the source (the Sun)propagates through the vacuum of space at the speed of lightinteracts with Earth's atmosphereinteracts with Earth's surfaceinteracts with Earth's at

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ESM 266: Multispectral remote sensing

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    1. ESM 266: Multispectral remote sensing

    2. 2 Radiation and remote sensing For example, if energy being sensed comes from the Sun, it: is radiated by atomic particles at the source (the Sun) propagates through the vacuum of space at the speed of light interacts with Earth's atmosphere interacts with Earth's surface interacts with Earth's atmosphere once again, and finally reaches our sensing system where it interacts with various optical systems, filters, emulsions, or detectors

    3. 3 Atmospheric absorption and scattering

    4. 4 Relation between frequency and wavelength

    6. Sun glint and wildfires near Carpenteria Bay, Queensland, Australia

    7. 7 Terminology Radiant flux F, units W Irradiance (flux density) E, units Wm–2 (called Exitance M when away from surface) Radiance L, units Wm–2sr–1 Note: All can be functions of wavelength and have units µm–1

    8. 8 Reflectance terminology

    9. 9 Relation between flux density and intensity

    10. Steradian (Solid Angle) The steradian (sr) is the unit of solid angle defined as: W = A/r2

    11. 11 Overview of typical system

    12. 12 Format of a multispectral image

    13. 13 Detector configurations: breaking up the spectrum

    14. 14 Characteristics of several sensors

    15. 15 Spatial, spectral characteristics of some multispectral sensors

    16. Sun’s radiant energy distribution

    17. 17 Landsat ETM+ spectral bands

    18. Band 1 (Blue: 0.45 - 0.52 mm) good water penetration differentiating soil and rock surfaces from vegsmoke plumes most sensitive to atmospheric haze Band 2 (Green: 0.52 - 0.60 mm) water turbidity differences sediment and pollution plumes discrimination of broad classes of vegetation Band 3 (Red: 0.63 - 0.69 mm) strong chlorophyll absorption (veg. vs. soil) urban vs. rural areas

    19. Band 4 (NIR1: 0.76 - 0.90 mm) different vegetation varieties and conditions dry vs. moist soil coastal wetland, swamps, flooded areas Band 5 (NIR2: 1.55 - 1.75 mm) leaf-tissue water content soil moisture snow vs cloud discrimination Band 6 (Thermal: 10.4 - 12.5 mm) heat mapping applications (coarse resolution) radiant surface temperature range: -100oC to +150oC Band 7 (NIR3: 2.08 - 2.35 mm) absorption band by hydrous minerals (clay, mica) lithologic mapping (clay zones)

    20. 20 Landsat 7 orbits and acquisitions, 4/30/2005

    21. 21 ASTER: Advanced Spaceborne Thermal Emission and Reflection Radiometer Launched on Terra 12/18/1999 4 VNIR bands 15m resolution, 24ş crosstrack pointing 6 SWIR bands 30m resolution, 8.5ş crosstrack pointing 5 thermal bands 60m resolution, 8.5ş crosstrack pointing See ASTER website for details

    23. 23 MODIS: Moderate Resolution Imaging Spectroradiometer Launched on Terra 12/18/1999, on Aqua 3/24/2002 Terra crosses Equator ~10:30 am, Aqua ~1:30 pm (orbit time is ~98 min) 36 spectral bands with resolutions of 250m, 500m, and 1km http://modis.gsfc.nasa.gov/about/specifications.php Global coverage 1-2 days depending on latitude Pointing, ±55° from nadir

    24. 24 Spectral signatures The spectral signature of an object in an image involves spectral BRDF of the object, i.e. fr(?, angles) (and other objects in the IFOV) (may change w time, e.g. vegetation in summer vs winter) the sensor’s bands, wavelengths, spectral and radiometric resolution, dynamic range scattering and absorption by the atmosphere in those bands amount of energy available (Sun or emitted) in those bands (A combination of physical and sensor characteristics)

    25. Atmospheric spectrum

    26. Snow, vegetation, rock: spectra of mixed pixels

    27. 27 Ice dam on Russell Fjord by Hubbard Glacier

    28. Ice shelf disintegration from MODIS Direct response to regional warming

    29. 29 ASTER: Erupting Mt Usu, Hokkaido

    30. 30 MODIS: Fires in southeastern U.S.

    31. Spectra with 7 MODIS “land” bands (250-500m resolution, global daily coverage)

    32. 32 Simple (snow/no-snow) algorithm for TM bands on MODIS Normalized difference snow index Thresholds for MODIS algorithm (Hall) If TMband 4>11% and NDSI>0.4 Pixel is >50% snow covered

    33. 33 Example: vegetation near Hudson Bay

    34. 34 Vegetation (NDVI) from Landsat image

    35. 35 Confluence of Tigris and Euphrates, Iraq

    36. 36 MODIS: Snow in northeastern U.S.

    37. 37 Data rate

    38. 38 Data rates of some sensors

    40. 40 MISR: Multi-angle Imaging SpectroRadiometer Launched on Terra, 12/18/1999 Exploits angular information in signal Surface BRDF Path lengths through atmosphere 4 spectral bands: blue, green, red, near-infrared 9 angles: 0ş, fore and aft 26.1ş, 45.6ş, 60.0ş, 70.5ş Global coverage 2-9 days depending on latitude http://www-misr.jpl.nasa.gov/mission/minst.html

    41. 41 MISR: Aerosol optical depth over central/eastern Europe

    42. Spectral solar irradiance

    43. 43 QuickBird: Commercial imagery at 0.6m resolution panchromatic, 2.44m multispectral

    44. NASA’s Earth Observing System (EOS): Idea of standard products Landsat, AVHRR, most earlier missions provide, at best, calibrated radiances at satellite Interpretation of these radiances to estimate geophysical and biological information requires arcane knowledge and difficult processing Need to understand relationship between electromagnetic properties of surface of interest and the properties of real interest Need to account for effects from atmosphere and sensor Need to deal with sensor geometry to provide information on a map base, so that you can integrate with other spatial information Therefore, EOS provides information, in addition to data

    45. MODIS the canonical (but not only) example http://modis.gsfc.nasa.gov/data/dataprod/index.php Each has a nontechnical description, information about the data, and an “ATBD” (algorithm theoretical basis document) Levels of processing Calibrated radiances and geolocation information Geophysical products Mapped to a projection

    46. MODIS Leaf Area Index

    47. MODIS FPAR (Fraction of absorbed Photosynthetically Active Radiation)

    48. 48 MODIS ocean chlorophyll, Indian Ocean

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