Lab 8: Spectral Signature Analysis

Goal and Background

This purpose of this exercise was to get some experience interpreting spectral reflectance of features on the Earth's surface from images taken by satellite sensors. We found the spectral signatures of various materials and surfaces in a remotely sensed image of Western Wisconsin.

Methods

Figure 1 - AOI in Lake Wissota

First, I digitized an area of Lake Wissota using the draw polygon tool (figure 1). Then, under the Raster toolbar, I clicked the Supervised drop-down menu and selected Signature Editor. This brought up the Signature Editor, where I could create a new signature from AOI (area of interest). Once this was added to the menu, I changed the name to Standing Water to differentiate it from the other signatures I would be collecting. Figure 2 shows the Signature Editor menu.

Figure 2 - Standing Water signature

From this menu, I could also display the Mean Plot window, shown in figure 3.

Figure 3 - Standing water mean plot

We were then tasked with finding the signatures of 11 more features using the same technique:

1. Standing Water
2. Moving Water
3. Vegetation

4. Riparian vegetation

5. Crops

6. Urban Grass

7. Dry soil (uncultivated)

8. Moist soil (uncultivated)

9. Rock

10. Asphalt highway

11. Airport runway

12. Concrete surface (parking lot)

Figures 4 and 5 show the signatures and the mean plots of all the features together.

Figure 4 - Signature of 12 features

Figure 5 - Mean plot of all 12 features

Results

The results demonstrated the difference in spectral reflectance between many different features and materials. A skilled remote sensing technician would be able to identify these features by their signature plots alone.