Exercise 6: Creating a Geodatabase

Why use Geodatabases and Domains?

GIS professionals use a lot of data that is typically stored in multiple sets of files. By using a geodatabase to store these files, they seamlessly share the same properties such as coordinate system, projection, and map units.  Domains help GIS professionals collect data quickly and efficiently without altering the data with human error. By setting up this infrastructure before the data is collected, much time can be saved both out in the field and afterwards in the lab when the data would need to be organized for analysis. 

In the near future, an exercise involving a microclimate map for the University of Wisconsin-Eau Claire will be conducted. Until the weather becomes more inviting, the most we can do is prepare a geodatabase and create specific domains to assist us during data collection and analysis. Variables we will be collecting include temperature, wind speed and direction, snow depth, dew point, and humidity. Each of these variables are recorded and formatted in different methods which means that domains will be need to be used to keep the values orderly. Temperature and dew point are recorded in integers, and it is safe to assume that the temperature on a given day will fall somewhere between -20 degrees Fahrenheit and 99 degrees Fahrenheit. In this case, a Float-Range domain will be created to only accept temperature values within the provided ranges. Wind direction can be collected in two formats, cardinal directions and azimuth bearing. When collecting the cardinal directions, a Text-Coded Values domain will be used to translate N to North, NW to Northwest, etc. Bearing azimuth is collected in degrees ranging from 0 to 360, and will utilizing a similar domain to that of temperature. Snow depth and humidity will be collected in amounts that could require decimal places, which makes Float the proper domain of choice. By creating a feature class utilizing these domains, data collection will be swift and unbiased by human error. 

Tutorial

This tutorial will explain how to create a geodatabase, create domains, and apply them to a new feature class within ArcMap 10.2.

A geodatabase is a collection of geographic datasets of various types, including feature classes, feature datasets, raster datasets, network datasets, tables, and more. The first step of creating a geodatabase within ArcMap 10.2 is to connect to the folder in which the new geodatabase will be located. Once the desired location is found, simply right click the folder and select New-File Geodatabase (Figure 1.). 

Figure 1. Many options regarding the geodatabase appear when the cursor right clicks the icon. 

Domains are rules that describe the legal values of a field type, providing a method for enforcing data integrity. For the purposes of this exercise, we are going to set domains that will help us collect accurate weather recordings for a microclimate map. To create a domain, right click the geodatabase and select Properties at the bottom of the drop down menu, and select the Domains tab inside the Geodatabase Properties window (Figure 2.). The top of the window shows two columns, one titled Domain Name and one titled Description. To create a domain, simply type a fitting name into the Domain Name column. A description is not necessary, it is only there to help you remember what the domain is to be used for. 

Figure 2. By opening the Properties of a geodatabase, the domains can be created and edited.

The first domain we will create for this exercise is one regarding rules for temperature values. The Temperature domain will be set to the Float field type because our temperature readings may contain decimals. By setting the domain type to Range, we can choose minimum and maximum values to set boundaries on our data. Taking dew point measurements into account, the minimum temperature value will be -20 degrees Fahrenheit and the maximum value will be 99 degrees (Figure 3.). This domain will be applied for both surface air temperature recordings and dew point temperature recordings. 

Figure 3. This domain will regulate values that represent temperature recordings. 

Another important domain needed to be created is one regarding time data. The time of each feature point will be recorded in a field titled Time. This field will require a domain that limits input values to the extent of military time. With the minimum value set to 0 and the maximum value set to 2400, an integer field type such as Short or Long can be used to allow whole numbers only (Figure 4.).

Figure 4. Integer field types are great for measurements with no fractions or decimals like time. 

Another domain we will use for the microclimate data collection will apply to wind direction data. This domain will have a Text field type and a Coded Values domain type. The use of coded values will allow us to simply type "NW" and the domain will recognize it as "Northwest". To create these associations, type a short code into the Code column and type the corresponding description in the Description column (Figure 5.). 

Figure 5. Coded values allow for quick and accurate data entry out in the field while minimizing human error. 

Once all of the desired domains have been created, simply press OK to close the window. In order to create a feature class, right click on the geodatabase that was created earlier and select New-Feature Class... (Figure 6.). For the microclimate exercise, we will be plotting individual points, causing Point Feature Class to be the desired feature class type. Near the end of the wizard, a window displaying field names and data types will be used to create fields and apply the domains we created earlier. I have created a field called Temperature and set the data type to Float. At the bottom of the window, a drop down menu reveals the domains that apply to float data types (Figure 7.). Simply select the corresponding domain and the newly created field will follow the rules set within the domain. 

Figure 6. Creating a new feature class from scratch allows the user to set specified domains and subtypes. 

Figure 7. Domains will not be applied to fields unless they are chosen within the drop down menu shown above. 

The final step of this tutorial explains how to import a raster into a geodatabase. Right click the geodatabase and select Import-Raster Datasets...(Figure 8.). A file explorer will appear and allow you to locate the desired raster. 

Figure 8. By right clicking the geodatabase icon, feature classes, tables, and rasters can be imported.