Exploring the ESRI Landsat App

Introduction

In order to get better acquainted with viewing satellite imagery, we explored the ESRI Landsat App. This app allows one to view satellite images that were taken all around the globe. They also can use false colors to view specific things within the image. Depending on the bands that are selected the app can do a series of different views, each one causing different things to become visible. Figure 1 shows the options one can use within the ESRI Landsat app.

Figure 1: Views available within the Landsat App

Exploration

Agricultural Rendering

The first view that was used was the agriculture view. This used false color to show where vegetation is and whether or not it is healthy. Figure 2 is of an area around Purdue, while using this agriculture view it replaces the color red with infrared. Healthy vegetation shows up as red in this view as water will hold IR energy and radiate that. Based on how much IR energy the plant is radiating will determine how red the plant shows up.

Figure 2: The Agricultural view around Purdue

Water Index

The next view that the tutorial had was of the water index. This view is a little different than the previous false-color image. This one takes values from many bands and uses calculations to find moisture. One can see that it uses the IR band to make these calculations as the spots on the map that showed up cyan in the agricultural view show up as blue in the water index view. Figure 3 is of an oasis in the desert. From orbit, the oasis can't be seen with the naked eye, but when the water index is turned on it stands out considerably.

Figure 3: Water Index over the Oasis

Temporal Perspective

The Landsat App also has another feature that can come in handy. The temporal perspective allows one to "look back" in time at old satellite images to see how the world has changed. Following this tutorial I looked at Las Vegas (NV) and Phoenix (AZ) Figure 4 is a side by side of Las Vegas, the image on the left is of the current view and the right image is of the earliest image available. Figure 5 is a side by side of Phoenix and follows the same positioning.

Figure 4: Las Vegas NV

Figure 5: Phoenix AZ

Further Exploration

After going through a few tutorials we were turned loose to create our own views and look at those views in different areas.  In order for the views to show up required some time for the software to process the desired band combination. Figure 6 is my first view that i created and i used the band combination 7,5,2. This caused the area to turn mostly lime green around West Lafayette so I was led to believe it was doing something similar to the vegetation index.

Figure 6: West Lafayette, 7,5,2

Figure 7 was a darker image with the band combination of 1,2,4. It was hard to tell what this one was showing so i stayed in the same spot, Ames, Iowa, and tweaked the combination to 1,4,6 and gave me Figure 8.  This one was still dark but bluer than the last which made me think that it also was highlighting vegetation just in blue this time.

Figure 7: Ames Iowa, 1,2,4

Figure 8: Ames Iowa, 1,4,6

Figures 9 and 10 are of Chicago IL and are pretty similar. The band combination used for figure 9 was 5,4,2 and caused vegetation to show up red and most of the image to darken. figure 10's band combination was 6,3,1 and just caused more red to appear.

Figure 9: Chicago IL, 5,4,2

Figure 10: Chicago IL, 6,3,1

Conclusion

By using this software it gives one an idea of how a UAS platform could better fill this role on a smaller scale. Sure with the Landsat App, one can view anywhere on the globe with any band combination one would want. The issue is with the satellite view the images don't have a very high resolution. Using a UAS platform with a multi-spectral sensor onboard could give you the same false color ability with greater more detailed resolution.