Lab 8 - Spectral Signature Analysis

For this lab exercise we were instructed to collect a number of spectral signatures from a Landsat ETM+ Image.  I did this using the signature editor, digitizing tool and signiture mean plot.  The image I analyzed is displayed below.

I found the following information on the features spectral signitures:
Standing Water:
Highest: band 1(.45-.52), Lowest: band 6(.52-.60)
Reflectance is highest in band one because this is the blue band in the visible spectrum.  After the first three bands, reflectance goes down significantly because there is very little outside of the visible spectrum.

Moving Water: Band 1 (.45-.52) has the highest reflectance

          Band 6 (10.4-4.5) has the lowest reflectance

Vegetation: Band 4 (.77-.90) has the highest reflectance

          Band 6 has the lowest reflectance

Riparian Vegetation: Band 4 has the highest reflectance

          Band 6 has the lowest reflectance

Crops: Band 4 has the highest reflectance

          Band 6 has the lowest reflectance

urban grass: Band 4 has the highest reflectance

          Band 6 has the lowest reflectance

dry soil: Band 5 (1.5-1.75) has the highest reflectance

          Band 4 has the lowest reflectance

moist soil: Band 5 has the highest reflectance

          Band 2 (.52-.60) has the lowest reflectance

rock: Band 5 has the highest reflectance

          Band 4 has the lowest reflectance

asphalt: Band 5 has the highest reflectance

          Band 3 (.63-.69) has the lowest reflectance

airport runway: Band 5 has the highest reflectance

          Band 4 has the lowest reflectance

Concrete: Band 5 has the highest reflectance

          Band 4 has the lowest reflectance

 

Shown below is a screen shot of all  of the spectral signitures in one graph.

Vegetation displayed high reflectance in band 4, which is the NIR band, and low reflectance in band   The reason that reflectance was so high on the NIR band was because there is a great deal of radiant flux energy reflected at this wavelength and there is a lot of chlorophyll on green vegetation.  In NIR, reflectance is high for green vegetation.

 Band five has the greatest variation between dry and moist soil.  This covers the wavelength range from 1.55 to 1.75 and is the short wave infrared band.  The reason that this wavelength has the most variation is because the shot wave infrared band picks up moisture content very well and can be used to distinguish between moist and dry soil.

Vegetation, crops and grassland are all similar in appearance because they peak at band 4, due to high reflectance in the NIR band.  Standing and moving water are very similar in appearance and have fairly low values across the board and are highest in band one.  Soils are similar but vary in band 5 due to different moisture contents picked up by short wave infrared.  Rock and asphalt are similar in appearance, as well as the runway and concrete.  There seem to be four distinct groups of patterns and each of the four are unlike the others.

It seemed like the most important wavelengths in this exercise were bands 1,4, and 5.  Band one is valuable in identifying elements like water, soil and vegetation.  Band 4 is valuable for analysis on the reflectance of vegetation.  Band 5 is important for analysis of moisture content, especially in soils and vegetation.  I think these are the three most important bands.

 Works Cited:

NASA Landsat Program, 2000, Landsat ETM+ scene, SLC-Off, USGS, Sioux Falls, 2013.