Spectral Signature Analysis

Goal and Background:

The goal of this lab was to show my ability to measure and interpret spectral reflectance of various Earth surface and near surface materials captured by satellite images. I collected spectral signatures from remotely sensed images, graphed them, and performed analysis on them to verify whether they pass the spectral separability test. 

Methods:
I opened a Landsat ETM+ image from 2000 of the Eau Claire area in Edras Imagine. I utilized the polygon tool under the Drawing tab to digitize an area in Lake Wissota. I then used the Signature Editor tool under Raster-Supervised.

In the Signature Editor I clicked Create New Signature from AOI. I changed its name and color and then displayed the mean plot window. I repeated these steps until I had spectral signatures for the following features:

• Standing Water
• Moving Water
• Vegetation
• Riparian Vegetation
• Crops
• Urban Grass
• Dry Soil (uncultivated)
• Moist Soil (uncultivated)
• Rock
• Asphalt highway
• Airport runway
• Concrete surface (Parking Lot)    

 
Results:

 Figure 1. This image demonstrates all of the spectral signatures collected together in the Signature Editor.

Figure 2. This image demonstrates the mean spectral signatures of the dry and moist soils. They follow each other almost parallel, but the difference between the bands is greatest around Band 5: 1.55-1.75 micrometers. This is likely due to the water in the moist soil, as water absorbs higher amounts of NIR, MIR, and FIR wavelengths.  

Figure 3. This image demonstrates all of the mean spectral signatures that I collected. Most of the vegetation is similar across the spectral channels, which makes sense because most plants absorb and reflect the same wavelengths of light. The asphalt, rock, soils, and runway are all fairly similar and reflect close to the same bands. This is most likely because they are made of similar materials and minerals. The water is the most different in its spectral signature because it reflects the least amount of infrared light. 

Sources:  

United States Geological Survey. (2000). Earth Resources Observation Science Center.