Geodatabases, Attributes, and Domains

Introduction

GIS at its very core is not just a set of geographic points, it is geographic data tied to other information. The analysis of this attribute data along with spatial data is what makes the core of GIS so applicable and useful as a tool. The goal of this assignment was to understand how data in the field is captured and implemented into a geodatabase. While this may seem like a straight forward process, having multiple people collecting data can be problematic and this may come from lack of standardization on many levels. The first thing to consider is how the data are going to be captured, and how people will be imputing values into the database. For example, do people record numbers as words, or by characters? Are directions put in as letters or words? While these discrepancies seem small, when it comes to implementing or analyzing data, these differences can cause incompatibility within tables and data sets. In order to eliminate these issues the constructor of the geodatabase must understand the data that will be collected and constrain the people in the field to record the data in a uniform way. This can be accomplished with domains, which determine the type of information can be recorded for each attribute, and how that information is to be recorded.  

Methods

In order to thoroughly understand why domains are important, not only were we to construct our own geodatabase and create domains for the attributes we would be collecting data for, we also went out into the field and attempted to capture GPS data for a micro-climate survey of the UWEC campus via ArcPad. The benefit of a mapping grade GPS is that not only can geographic points be captured but attribute data can be multiple users collecting data can be aggregated in a usable way in one geodatabase. But, as stated before, in order for that data to be usable the data inputs and entry must be standardized such a way that data is usable with out post processing. The attribute data that we would be collecting for the micro-climate survey are; group number, temperature, date, cardinal wind direction, azimuth wind direction, dew point, relative humidity, and a notes field. After creating a geodatabase and these attribute fields, we applied domains to the fields such that each field would be limited to a standardized input of our choosing (Fig 1).

Fig 1. Creating Domains in the geodatabase. 

After creating the geodatabase, we added a image from the Eau Claire County geodatabase of imagery of the area (Fig 2). It was very important to have a clear and concise file path structure such that all data would be organized and data coming in from the field would be in a easy to locate location (Fig 3)

Fig 2. The survey area of the micro-climate survey, the UWEC grounds, outline in red.

Fig 3. The filepaths for the micro-climate survey data, related maps, image files, and geodatabase. 

The next step was to prepare that data for deployment by turning on the ArcPad Data Manager, and transferring the geodatabse and the image file to the Juno unit for GPS data collection (Fig 4).




Fig 4. Setting up ArcMap to deploy geodatabase, and thematic layers to Juno Device via ArcPad Data Manger.

Then we were to go out into the campus mall and capture data with a Juno handheld device which had ArcPad installed, and use a kestrel to capture information on wind direction, temperature, dew point and humidity (Fig 5)

Fig 5. Kestrel and Juno device for data capturing. Juno displays the Image file of campus that was loaded during the data deployment step.

Results/discussion

The exact study area was the University of Wisconsin Eau Claire campus mall, in Eau Claire Wisconsin. The weather outside was overcast and rainy, with a slight wind, and the rain was slowly turning to snow. After we arrived at the campus mall we had to turn on the location ability of the Juno device so that our positions could be recorded and we received a short demo from Dr. Hupy on the use of the Juno device (Fig 6).

Fig 6. Dr Hupy showing us how to use the Juno.

While the data collection went smoothly for most people, I ran into an early problem. When attempting to capture GPS data, I of course had to fill out the attribute fields that went along with each position. Everything was going well until I hit the notes field, which became auto filled with a <Null> value and would not let me capture a data unless the field had information in it, which the field would not let me input. This was a problem because, not being able to input any information as the notes field being empty would not allow data to be collected. After being generally confused about this and trying to figure it out for a few minutes, Dr. Hupy told me that it was because I probably had applied a domain to my notes field, which made it unable to record any information (Fig 7). Due to the fact that this was occurring I was unable to capture any GPS data and therefore unable to upload any data points to my map. For this instance not capturing data was okay, due to the fact that this was a trial run to understand how hard it is to create a geodatabase and implement domains to deploy in the field. In our next exercise we will be doing an actual microclimate survey, where we collect data in a pre-constructed geodatabase , with domains that have already been set up.

Fig 7. Error occurring as I had applied a domain to the notes filed, which did not allow for any entry.

Conclusion

I know now how hard it can be to capture all of the attribute data that makes GIS so useful, and why it is so important to make sure that the captured attribute data is normalized. With out capturing attribute data, GIS would just be a series of GPS data points with no functionality and would just be something to create maps with no information other useful information. But just capturing attributed data is not enough, in order to make sure that the data is useful, it has to able to be stored, deployed, and recorded in a way that anyone can use or record the information. For this to be possible the geodatabse that the information is recorded into or deployed from has to be set up in a usable and straight forward fashion that makes adding or using the data easy, and non-complicated for anyone to use.