Activity 4: Geodatabases, Attributes, and Domains

Introduction

In this week's assignment, I was to create a geodatabase that would in turn be deployed in ArcPad. This geodatabase will be used to create a microclimate map which then will be a part of an activity down the road. The geodatabase needs to contain various data for each point taken in the field. These data attributes include: temperature, dew point, wind speed, wind direction (cardinal and azimuth), group number, relative humidity, and the most important being an attribute for note taking. It is important to create a good geodatabase with valuable domains before heading out into the field. Having domains allows for easier and quicker data collection as well as reduces the potential of incorrectly inputting values for different attributes. This activity also helped to be able use ArcPad to collect different data for the micro climate around campus and to import that data into ArcMap. It is important to properly create a geodatabase because an activity such as collecting micro climate data is supposed to take as little time as possible as to avoid discrepancies in the data due to temporal variances. It is also important to practice good normalization as to avoid problems and headaches when manipulating data back in the lab.

Part 1

The first step is to get ready to create a micro climate geodatabase. In order to do so, one needs to plan ahead and figure out the attributes that are required or important before heading into the field. It is crucial to have the proper tools and a Trimble Juno GPS unit (figure 1) is one of the most important tools to have for a project such as this. This allows for a geodatabase to be uploaded to the mobile device and allows for data to be collected and surveyed on the fly in a more or less mobile version of ArcMap. As mentioned before, it is important to plan ahead and figure out the different attributes that are important to collect to get a nice understanding of different microclimates. For this activity, it is important to understand what a microclimate is. A microclimate is a small restricted area that varies in temperature, humidity, wind speed, etc. (climate) of another climate or area nearby.

figure 1: The Trimble Juno GPS unit that will be used for data collection later on. 

Part 2

Step 1 - Construction of a Geodatabase

This is probably one of the fastest steps of the whole process. I first had to go into ArcCatalog and create a new file geodatabase in a folder I created. Now my geodatabase was created (figure 2).

figure 2: The new geodatabase named 'mc_hagenjc.gdb' that will be used to collect and analyze the data from this project

Steps 2 & 3 - Development of Geodatabase Domains/Development of Domain Ranges

This step is very important because it helps save time and reduces the chances of making user errors when inputting values, as mentioned before. By looking at the data that will be collected, one can determine what the domains (a set of rules assigned to a given attribute) and ranges will be set as (figure 3). For example, temperature was given a range of 15-60 degrees Fahrenheit so values that lie out of this range will not be recorded. Coded values were also used for wind direction, so recording an N would imply that the wind direction was north, and SW would imply southwest. It is good to observe the attributes you decide to collect as well as when and where they are collected. It would be cumbersome and possibly problematic to set a range of -50 to 150 for temperature in spring because temperature will most likely not reach a value near -50 or 150. That is why I chose to use a range of 15-60 for the time of year I would be collecting data. When creating domains, it is important to create a description in order to know exactly what the domain is, especially if you decide to abbreviate domain names. On top of that, the knowledge of data type must be understood. For instance, what implications short integer, long integer, float, and text have on the data being collected.

figure 3: Example of a domain name, description, field and domain type, and domain range

Step 4 - Construction of a Feature Class for Later Deployment in ArcPad

After the domains have been created, it is time to create a feature class. A feature class is collection of features that all have the same spatial representation such as a point, line, or polygon and a common set of attribute columns. For this activity, a point feature class was created with a UTM zone 15 projection. It is important to note that only one feature class should be created, otherwise you would have to filter through numerous feature classes in the field for each attribute.

Step 5

I decided to add another step by importing an aerial basemap of the study area. The basemap should be zoomed in to the desired area to avoid pixilating the image as well as to prevent the Trimble from taking a long time to buffer the image. I figured having a basemap would help for easier navigation around the campus and to make sure I was in an accurate location on the map as compared to the field.

Discussion

It can be easy to create a geodatabase if you know what you are doing. But it appears you can potentially run into a plethora of problems such as using a short integer when a long integer is required, or not properly setting a domain range. These types of errors can easily be avoided by planning ahead for the project and determining best practices ahead of time. On top of that, human errors can also occur in the field so that is one importance of setting domains to combat those user errors. It is hard to keep in mind to use best practices to make data interpretation not only easy for yourself, but also for other people who could potentially use the data you have collected. So I have been trying to keep in mind to write out detailed descriptions and try to make sure that another person could understand my data and use it without running into problems that could have easily been avoided if I were more careful and conscientious in pre-planning.