Geodatabases, Attributes, and Domains
Introduction
Proper recording techniques and field reconnaissance are not achievable without first determining a game plan and then properly laying out tools with which to accomplish organized recording. This statement is no different when comparing the act of scribbling notes into a Rite-in-the-Rain or logging notes into a Trimble Juno handheld GPS unit, equipped with ArcPad to record precise location and a multitude of attributes. For a researcher and collector of data to acquire the best possible notes in a given situation, preparation and organization are key. I have a specific way that I record my notes into my field notebook. I start by filling out the lines on the top of the Rite-in-the-Rain pages; location, date, project/client. Then, on the first few lines, I will record the time, current weather conditions, and predicted weather conditions. This will help me to recall conditions after I have returned from the field. I will make changes to this depending on my task. If I am conducting a soil pit profile I will likely record if there has been significant rainfall or a lack of rainfall in the recent past. This also is pertinent in I am on a river and the stage is higher/lower than average because of recent precipitation. Within my notes I will record things a certain way. If I traverse a number of sites while at one location I will indent all of my notes after my site number and location. I will do the same if I am describing a soil profile. This allows me to see clear breaks between different locations and different attributes.
The same type of preparation and methodical style exists with the Trimble Juno 3 Series handheld GPS devices that we deploy into the field. If the feature classes and geodatabases deployed with the unit are not properly set up, proper data collection becomes a nightmare. On the other hand, if proper organization and setup methods are observed, the ability and ease of use for the units increases significantly. Proper geodatabase setup essentially encapsulates the entire issue of proper organization and data collection. A geodatabase is "the native data structure for the storage and analysis of geographic information. Just like maps contain a collection of many thematic layers, the geodatabase is a collection of thematic datasets" (Zeiler and Murphy, 2010, 7). Geodatabases allow for advanced functionality and setup of many different components such as feature classes and datasets, raster datasets, toolboxes, and a plethora of other components. Within the Properties of a geodatabase, a highly powerful setup tool known as Domain is available for use. Domains are basically a set of rules that describe the acceptable values for feature classes within a geodatabase (ArcGIS Help, 2012). Domains help to reduce the potential for inaccurate data recording and also help to automate and standardize recordings. For example, this geodatabase is being created to aid in an exercise where accurate temperature recordings will be key to recording accurate data to develop a microclimate of the University of Wisconsin-Eau Claire campus. A domain allows me to set the range of acceptable values between -30°F and 60°F. If, while in the field, I was attempting to record a temperature of 21°F, but accidentally entered 221°F, a properly setup domain would not allow that recording to be input.
As a class, we discussed the necessary components to make this geodatabase functional in the field, for our purposes. We determined that the following domains were necessary (ranges and units listed in parentheses): Wind Speed (0 to 50 mph), Wind Direction (0 to 360°), Humidity (%), Dew Point (-30°F to 60°F), Temperature at the surface (-30°F to 60°F), Temperature at 2 meters above the surface (-30°F to 60°F), and Wind Chill (-30°F to 60°F). Ground Cover was another domain we set up that dealt with coded values, rather than ranges. Coded values use a list of different codes to correspond to a unique value. The coded values with their corresponding values listed in parentheses are: Grass (Grass), Snow (Snow), Con (Concrete), BT (Blacktop), OW (Open Water), Grav (Gravel), Sand (Sand), and Other (Other). When inputting values, these codes allow for quick and easy recording of the different types of ground cover we encounter. A final field for Notes was added to help explain anything that we need to in the field that is not covered already by the domains and fields created.
Methods
Proper setup of a geodatabase, domains, and a feature class are quite easy and save a lot of issues in the future.
- Open ArcCatalog through the stand-alone program or through ArcMap.
- Navigate to and select a folder for storage.
- Right click the folder and select New --> File Geodatabase (Figure 1).
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| Figure 1. This image shows where to find the option to create a new File Geodatabase within the ArcCatalog sidebar in ArcMap. |
- Name the geodatabase.
- Right click the geodatabase and select New --> Feature Class.
- Right click the geodatabase and open Properties, found at the bottom of the menu.
- The right tab will be called Domain. Click the tab (Figure 2).
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| Figure 2. This shows what will open up when the Properties menu of a File Geodatabase is selected. Domains can be created and assigned here. |
- Create the desired domains.
- Assign ranges or coded values as necessary (Figure 3 and Figure 4).
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| Figure 3. This shows the File Geodatabase Properties menu after it has been populated with domains. The selected domain is an example of a range domain, with a minimum value of -30 (degrees Fahrenheit) and a maximum value of 60 (degrees Fahrenheit). |
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| Figure 4. This shows the File Geodatabase Properties menu after it has been populated with domains. The selected domain is an example of a coded value domain. This lists specific codes that correspond to other values. This example is for ground cover types. The list on the bottom of the figure is where the coded values are input and the descriptions are listed. |
- After domains are created, assigned ranges/coded values, and described, close the Properties menu.
- Right click the geodatabase and select New --> Feature Class (Figure 5)
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- Give a name and create a point feature class.
- Assign a projection relative to your location.
- Create fields to correspond to the domains created previously (Figure 6).
- Select the proper domain from the bottom of the window where it says "Domain."
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| Figure 6. This shows the Feature Class Properties' Fields tab after it has been populated with domains. |
- Make sure to select the proper Data Type for the proper fields (Figure 7).
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| Figure 7. This figure shows the different types of numeric data types available. Short and Long integer are not able to contain decimal places, while Float and Double are (ArcGIS, 2013). |
- When recording data, all of these fields will be able to be populated. If the range is exceeded the record will not be input.
- Close out of the Feature Class Properties window.
- Close ArcMap/ArcCatalog.
Conclusion
Proper planning and organizational skills are key to accurate, easy to read, standardized field data collection. In this exercise, we developed a geodatabase with domains and a feature class. The domains assign allow for a range or coded set of values to be input into the corresponding field within the point feature class. This reduces the potential error and standardizes responses for the field. If these steps are not undertaken, the method of data collection and recording has the potential to contain errors and differences that make the data not similar when analyses begin later.
References Cited
ArcGIS Help. (2012, February 10). A quick tour of attribute domains. Retrieved March 1, 2015, from http://resources.arcgis.com/en/help/main/10.1/index.html#//001s00000001000000
ArcGIS Help. (2013, July 30). ArcGIS field data types. Retrieved March 1, 2015, from http://resources.arcgis.com/en/help/main/10.1/index.html#//003n0000001m000000
Zeiler, M., & Murphy, J. (2010). Modeling our world: The ESRI guide to geodatabase concepts (2nd ed., p. 7). Redlands, California: ESRI Press.
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