Lab Four: Geodatabases and Domains

Introduction:

This lab was centered on creating a geodatabase with custom defined domains for different data types. This database was then downloaded to a handheld GPS unit and used to collect weather observations around the UWEC campus mall.

Methods:

This geodatabase needed to store domain information for a feature class with custom made fields to store microclimate information; for example, temperature, dew point, relative humidity, wind speed, and wind direction are all examples of the data types collected. For each attribute it was necessary to set a domain or subtype to normalize the data across multiple surveyors. An example of a domain would include setting a range for the wind speed field; it would be outrageous to accept a wind speed of -2 or 6666666, so the range was set to only accept values between 0 and 60, inclusive. The other type of domain setting was for a coded index domain, essentially an attribute field where there are a few predefined choices available for use.

Field Name	Data Type	Domain Type
Group Number	Text	Coded Values
Point Number	Short Integer	Range: 1 to 100
Temperature	Float	Range: 15 to 60
Dew Point	Float	Range: -20 to 100
Relative Humidity	Float	Range: 1 to 100
Wind Speed	Float	Range: 0 to 60
Cardinal Wind Direction	Text	Coded Values
Azimuthal Wind Direction	Short Integer	Range: 0 to 360

Table 1. All domains and associated data types used to create this geodatabase. Note that Dew point has a range that was changed to a negative value.

 An example of this was from the group number attribute; allowing the user to only select from a pre-defined list of options. After entering domains, we tested the functionality of the geodatabase and feature data set described earlier by importing it to a Trimble Juno GPS unit set up to run ESRI’s ArcPad GPS program. Observations were collected from the UWEC Campus Mall, an area roughly 500 by 200 feet in the center of the UWEC campus located in Wisconsin. Using the GPS unit and a Kestrel 3000 wind meter, a handheld weather monitoring device capable of collecting all required data, a couple points were created and the attribute table was populated.

Results/Discussion

When entering data points to the feature dataset it became apparent that several adjustments were needed; for example, the dew point attribute domain needed to have an extended range as several dew point measurements had negative values. Because of this the correct value wasn’t able to be entered for the points in the dew point field. All other fields worked well with the domains being set up for the weather present on that particular day. Unfortunately there were only two points collected for the time that was allotted for data collection. This was due to the fact that the GPS unit I was assigned failed to acquire a strong enough signal from satellites meaning that what points I did collect were recorded as being several kilometers south of where they should have been. 

 

Conclusions:

During this lab the processes required to create a geodatabase with relevant range and coded value domains were completed. From here it was a relatively simple process to export this geodatabase with its point feature class into a Trimble Juno GPS unit for a short test. During the test it was apparent that the domain range for the dew point attribute needed to be extended and that one cannot always trust their equipment to work correctly once in the field.