Section Six: ArcGIS File Naming Rules

Since ArcGIS is a database program, and because databases have strict rules for file names, ArcGIS also enforces some pretty strict file naming conventions.

The first rule of naming files in ArcGIS is:no spaces and no special characters (except an underscore _ ).
    • This is true for everything in ArcGIS; file names, field headings, custom tool names, etc.
    • If you attempt to save a file with a space in the name, ArcGIS will return an error, stating the file name is incorrect and must be addressed before you can move on.
The second rule of naming files in ArcGIS is:no spaces and no special characters (except an underscore).

There are three exceptions to this rule:
    1. File name aliases. You can give your layers “reader friendly” names for use in legends. File name aliases are not really the name of the file; think of them as a graphical representation of the actual file name.
    2. Folder names: ArcGIS will let you name folders with a space, but it’s a good habit to not do so. There are some tools that will fail with a space in a folder name; you won’t see them in this class, but again, GIS 101 is preparing you for a lifetime of GIS.
    3. Final products. PDF, jpg, tiff, etc. map outputs can have spaces since they are not being put back into ArcGIS. Follow any other protocol in place when it comes to naming final products.
As you see, the three exceptions are in regards to files or situations other than naming GIS files
The third rule of file naming in ArcGIS:Do not start file names, field headings, folder names, or MXD names with a number or underscore
    • This rule is to prevent any sort of file confusion within the software. The tools and processes behind the scenes are not fans of spaces and underscores as file starters.
Geodatabase Rules
  1. Feature class or table name length: 160 characters
  2. Field name length: 64 characters
Shapefile RulesShapefile name length: 10 characters
Raster Rules
  1. Raster Field name: 13 characters
  2. Total length for raster and path name: 128 characters

4.6.2: Saving Properly When Running the [insert name here] Tool

Every time you run a tool in ArcGIS, there will be an “Output Location” box. This box is tells ArcGIS where to save the output of the tool after it runs. Since we know the second function of our “Results” folder is a place to save the output from any tool you may run, we already know the path to save to.  To designate a place to save the output, click on the folder icon GenericOpen_B_32-display to the left of the input box and drive to your results folder (keep opening folders until you get to your destination).

Once you’ve opened your results folder, you need to give your output file a memorable and meaningful name. ArcGIS will default to the name of the tool (buffer, clip, erase, etc) appended to the original file name, which is neither memorable or meaningful. It is your job, nay, your duty, to rename the file according to your goal and task at hand, for example, “River_Buffer_50_meters”.

Figure 4.15: The Buffer Tool Dialog Box Showing the "Output Feature Class" Box Blank and Filled In.

4.6.3: Default Geodatabase

ArcGIS creates a default geodatabase for each user of the computer in their "C:\Users\username\Documents folder.  The purpose is to create a default place to save the output from geoprocessing tools (the tools we use in ArcGIS to analyze our data).  Since ArcGIS really wants you to work with the geodatabase format over a folder based system, it sets itself up from the beginning to use such a system.  A good practice is to re-assign the default geodatabase for each project to either the geodatabase for that specific project or a catch-all default geodatabase saved somewhere other than the default location.

One of the most common mistakes new GIS technicians make is clicking too fast and not assigning an location or memorable and meaningful name to the tool output, which leads to a whole series of "lost" data all named "Export_Output1", "River_Buff_Diss_1", and the super helpful "Export_Output2". facepalm.  Until you memorize where the default geodatabase is on the computer as defined by ArcGIS, it will seem like all the data is "lost" or "just gone, I don't know what happened", yet its not really lost, it's just in the default geodatabase.  One of the best moves you can make when you start a project is to re-assign that default geodatabase to one you know where it lives.  In lab, you will create and use a default geodatabase saved right inside your GeoGoonies folder.  

ArcGIS Help Article on Default Geodatabases