This demo relates to the GSP 270 Lab activity,
Planning a Homestead. The instructions are located on the Humboldt
State Geospatial Online web site. I’ll post a link to the instructions in
the video description. The first step in any of these lab activities
is to create a basic folder structure. Typically, this will be placed on your local
hard drive. On a personal computer, this would be the
C drive. If you are in one of the labs at Humboldt
State, then it will most likely be the D drive. In this example, I am using the downloads
folder on my local C drive. I’ll start by creating the top-level folder,
which should indicate the lab assignment. Within this folder, I will create three subfolders,
original, working, and final. Now I am ready to download the data. Right click on the DEMs For Arcata link. Select Save link as, then navigate to your
original folder. Save the compressed file inside your original
folder. Open your original folder. You will see the data saved as a compressed
zip file. Go ahead and decompress the file. Delete the original zip file when you are
done. You should see a folder called Terrain Data. Within this folder, you will two sets of data
compressed as a tar.gz file. You will have to decompress it twice to get
to the data. Right click on the tar.gz file, select 7zip,
then extract here. Then, right click on the .tar file and decompress
it. Delete the original tar.gz and .tar files. It saves space and helps to prevent confusion
later. As you can see, this raster file format contains
many component files to make it work. Repeat these steps for the second tar.gz file. In ArcMap, open a blank map document. The steps in this activity involve using the
Spatial Analyst extension. To make use of the tools that come with this
extension, you must be sure it is activated on your computer. From the menu at the top, go to Customize,
then Extensions. Check the box next to Spatial Analyst. If you fail to do this step, you will encounter
a licensing error message when you try to run the tools for this activity. In the ArcGIS software, the Background Geoprocessing
setting is often turned on by default. This setting allows users to continue to work
while a tool is running in the background. However, sometimes this setting will stop
tools from running or cause other unforeseen problems. To reduce that chances of the ArcGIS software
crashing during this exercise, I recommend turning this setting off. Open the Geoprocessing options from the Geoprocessing
menu. Under Background Geoprocessing, uncheck the
box next to the word Enable. While you are setting things up, take a moment
to enable store relative paths and save your map document. The easiest way to add data is to use the
catalog window. You’ll typically see the catalog window
pinned to the right side of the screen. If you don’t see it, just click the button
with the yellow file cabinet icon. When you first open the catalog window, you
may not see the project folder right away. If you don’t see it, you can add it using
the connect to folder button. In this example, I am going to connect to
the downloads folder so that it will appear in the catalog tree. Now I can access anything in the downloads
folder right from the catalog window. Unlike previous lessons, I won’t add this
data to the map. Instead, I will show you how to convert the
files to a format that is easier to work with in ArcMap. Navigate to your TerrainData folder. Right-click on the DDF file that starts with
9945 and select Export, then Raster to Different Format. For the output click the yellow file folder
icon and navigate to your working folder. Call the file, “Arcata_North.img. You will have to add the .img extension manually. Adding an extension like “.img” makes
things run more smoothly and prevents some errors that may occur without it. Under Pixel Type, change the type to 32 bit
float. Leave all of the other settings as default
and click OK. A digital elevation model for the Northern
part of Arcata is now added to the map. Repeat these steps for the DDF file that begins
with 9946. Call the output “Arcata_South.” In the next video, I will show you how to
use the Mosaic to New Raster tool to create a single digital elevation model out of the
two datasets.

Planning a Homestead Part 1: Setting up Your Workspace

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