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Geospatial data comes in a wide variety of formats and specifications that have been developed by various countries, federal and local government agencies and software engineers over the period of several decades. Some have gained wide spread adoptions such as ESRI's Shapefile format. And some are used for very specific data products such as the U.S. Geological Surveys DEM or digital elevation model. Which is an open standard used around the world for sharing elevation data. While there are hundreds, if not thousands, of different ways that your geospatial data might be stored. There are some very common handling procedures that you should be aware of that differ from how you might work with other files on your computer.
The first thing that you need to be aware of is the fact that a single data source might be stored in dozens of interrelated files on your computer. And each one needs to know exactly where the others are. For instance, inside of our Data Files folder, you'll see a folder for global data sets that I've given you. And inside of here are a whole bunch of files that all share the same name. For instance, this group here that all ends in the word airports, all of these files are connected. And if one file in the group moves or is renamed, it can corrupt the entire data source, there's also a folder here that ends in .gdb.
This is data stored in a geodatabase format. And inside of this folder are all the files that are required to make it work. For this reason, you should only work directly with geospatial data files inside of a program that is designed to manage these connections for you. In the ArcGIS suite, that program is called ArcCatalogue. And we'll take a look at that later in the course. The second thing to be aware of is that the map documents that we'll be assembling end in a .mxd file extension. Let's go back up a couple folders, and I'm going to go into this Chapter 00 folder.
And inside of here you can see a file called reconnect.mxd. This is one of our map documents. These files store information about the presentation of your data including layout and colors. They don't store any information about the actual data that you are mapping. Instead, they link to the data sources that are stored. So once again, if something moves or gets renamed, your map document mxd files might lose track of the data. In this case, it's a simple matter of reconnecting or telling your map document where the data moved to. So, I'm going to go ahead and open up this Reconnect file, and that'll start up ArcMap.
Now, in moving the course exercise files to your computer, it might be the case that your file path will be different than mine. And you'll need to reconnect the map documents to the data files it references. I've gone ahead and opened up that Reconnect file, and you'll notice that there's nothing here, in the middle of the screen. And over here, on the left-hand side, I get this red exclamation mark, next to the data source. This means that the document has lost track of where that data should be coming from, and it needs to be reconnected. To do this, simply click on the tech box to turn it off, and then click again to turn it back on. Then you'll get this Set Data Source window that opens.
Now if I use this drop down list here you'll notice that it's a little bit different than what you might be used to from Windows. For instance, you don't have access to your C drive. What I need to do here is go to this button right here with a little plus symbol that says connect to folder. I'll click on that, and then I'll browse out to my desktop. I'll select the Exercise Files folder, and inside of there, I'll click on the Data Files folder, and I'll press OK. That'll add data files to this list of sources here. Now once I have that connected, I can go into the Global folder and choose that airports file that we were just looking at in order to reconnect it.
And all you have to do here is just match up the names. Go and say Add, and now your files are reconnected. Now I've tried to create these exercise files in such a way that you probably won't have to deal with missing data references. But I can't predict your specific computer setup. So if you do need to reconnect the data rest assured that you only need to do it once per file. And after saving the map document the new file paths for the data will be stored from that point forward.
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