|Reflectance spectra for 5 surface materials.
For vegetation and water, note the huge difference betweenthe red and NIR bands.
|Normalized ratios can be used to differentiate surface
materials. For instance, the NDVI takes the difference
between red and NIR bands (3 and 4 for Landsat 7, 4 and 5 for Landsat 8) over their sum. Vegetation will be
low in the red band 3 and high in the NIR band, leading to a very large
value of the ratio. Non vegetation, like soil or rock in
the spectra above, will have very similar values in red and NIR and hence a low NDVI ratio.
Ratios can deal with different total illumination resulting from different solar elevations and partial shading.
|With enough detail in the spectra, note that different kinds of vegetation can be discriminated.|
Reflectance spectra, available in ASCII format (ASC extension) from USGS Spectroscopy Lab (version 6a), should be placed in a x:\mapdata\spectral_library directory. They can be plotted from
Last revision 1/17/2018