Lab Eight: Calculating Impervious Surface Area

Introduction

In this week’s lab, we started out by visiting the ArcGIS online lesson gallery and selecting,

Calculate Impervious Surfaces from Spectral Imagery Tutorial. From here we needed to download

the tutorial onto our computers and put them in to correct locations as necessary. I was able to move

everything to my local drive and when I was finished, I moved everything to my student folder in the

classes drive.

 Methods/ Tutorial

The first thing once we opened ArcGIS Pro and the data was opened into there was to

“extract bands.” I was able to do this by using the “extract bands” option as seen in (figure 1).

Figure 1 (Extract Bands Function)

As seen from above, you can see that vegetation, roads and houses are all distinct colors but,

all the related to one another so it is easier to classify them. 

Moving on, I was able to work with the classification wizard. In simple terms, the classification wizard lets you denote comparable recipients to one color so that it is more accessible to know what things are to one another. In technical terms, this is being able to segment the image. By doing this, you are able to group similar pixels together. There are multiple steps to go through while working through the classification wizard. 

The next thing I was able to do was to classify the imagery (figure 2). On this step, I need to “circle” out points that were the same thing. For example in the picture below there is a small pond and a big bond. When I circled these out, I classified them as both “water.” This lets the program recognize different things from one another (roads, water, grass, etc.)

Figure 2 (Classification Wizard) Classify The Imagery 

Once the items were classified, I was able to change the colors of the sample to better distinguish the map (figure 3). With the classifications I have set and the wizard being completed, click run and a new layer is added.

Figure 3 (Classification Wizard Continued)

There are definitely some mistakes in the new layer. You can see that in figure 3 some buildings

are blue (depicted as water) when they shouldn’t be. Since this was a tutorial I was not worried no

had the time to rerun the program to correct for errors. 

The final thing we did was reclassify errors. For this, all you have to do is select the areas that were classified wrong and tell the program what it should be (impervious vs pervious), as seen in figure 4. Depending on how perfect you want your to image to be, this step can take up to multiple hours to make sure that everything is classified correctly and even then, it won’t be a hundred percent.

Figure 4 (Impervious vs. Pervious Depiction)

Conclusion / My Final Product:

Overall, this was a helpful tool to use as I was able to learn more tools to use on ArcGIS Pro.

From this tutorial, I was able to create a map (figure 5) showing the different classifications and

the differences between the impervious vs pervious surfaces. 

Figure 5 (Final Map Created From Tutorial)