Sunday, October 25, 2015

Thermal & Multispectral Analysis - Barren Soil, Guayaquil, Ecuador

For this lab I conducted an analysis of a particular feature using Thermal & Multispectral tools. The primary goal was to use both ERDAS Imagine and ArcMap to adjust band combinations to highlight a feature of my choice. I created a composite image in ArcMap using a LANDSAT ETM image of Coastal Ecuador.  (Data Management Tools > Raster > Raster Processing > Composite Bands). At first I examined each band separately. For Band 6, the Thermal Band, the image remained mostly the same as in all the previous bands, only it appeared more “fuzzy.” The thermal return indicated that my feature was quite warm. This told me that it was a material (bare earth) that was emitting a good deal of heat. Knowing that I was viewing a feature very near the Equator, I surmised that this feature was emitting retained heat from the sun. I could also venture to say that this image was not taken at first daylight since the bare soil was already at least "warm".  I would guess the bare soil had absorbed at least some sun energy and therefore the time of day was at least past mid-morning. Additionally, I could not detect any significant shadows so this also told me the sun was probably at a high angle overhead. After viewing each band separately, I used various band combinations to further examine the image including:

False color – 4-3-2
Natural color – 3-2-1
Healthy vegetation – 4-5-1
Near IR, Mid IR, Red – 4-5-3

I finally decided to use the Band combination of 7-4-2 to display the final map analysis. This combination provides a "natural-like" appearance of many features. Healthy vegetation is bright green, grasslands appear green, pink areas represent barren soil, oranges and browns represent sparsely vegetated areas. Hence, the feature I selected in this map of Guayaquil, Ecuador is a patch of barren soil surrounded by healthy vegetation and water.

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