Spectral signatures

Electromagnetic radiation is changed by the atmosphere, but reflectance (the bulk of satellite imaging for mapping) depends greatly on the spectral signature of the material reflecting the incoming radiation.

Resources for spectral signatures

• Compare satellite bands and material spectra. Launch viewer here
  https://landsat.usgs.gov/spectral-characteristics-viewer
• Here’s a site with a spectral comparison of some satellites and some earth materials
  http://www.physics.nus.edu.sg/~crisp/cd2001/tutorial/optical.htm
• spectral plots of minerals ( tons! ) and many landcovers (at the bottom of the list)
  http://speclab.cr.usgs.gov/spectral.lib06/ds231/datatable.html
  like these two likely soils constituents and land covers

  hematite	Montmorillonite
  Rangeland (here)	Wetland

Example Use of Specctra: Using TM to map Geology in Utah (http://rst.gsfc.nasa.gov/Sect13/Sect13_4.html) well… that NASA link is broken…so these guys mirrored it (? http://geoinfo.amu.edu.pl/wpk/rst/rst/Sect2/Sect2_1.html)

Let’s poke around in Lexington. Go here, choose the  Landsat Explorer app
http://www.esri.com/landing-pages/software/landsat/unlock-earths-secrets

• grass
• pavement or buildings
• water (silty vs clear?)
• pine
• deciduous (summer vs winter?)
• pastures (summer vs winter?)
• bare soil

Then change the time of year! Leaf on? Leaf off?  How about a desert? What do we see there?

Where else are you curious about “multispectral” (multiband) reflectance? Let’s go there!