Database Creation for Micro-Climate Mapping

When starting a geospatial project, it is import to consider exactly what data you are going to be collecting for the project before you venture off into the field. By planning an organized geodatabase, the data collected from the field can be imported into ArcGIS in a more user friendly manner. In this GIS exercise, a geodatabase will be created to hold data about micro-climates around the University of Wisconsin-Eau Claire campus.

 How can a geodatabase be used in the field?

 New hand-held GPS units are becoming portable computers. A user can create feature classes and log data directly into a database out in the field without needing a full version of ArcGIS. These features, however convenient they seem now, can be a double edged sword. If multiple feature classes are created “on the fly” in the field, data are separated into those separate feature classes. If the user considers what they want to record for data before leaving the lab to the site, all the data can be logged into a singular feature class. Creating feature classes out in the field also can lead to input data errors which can misrepresent information, costing more time in the future. Using a singular feature class that holds all the attributes one wishes to record in the field, stores all the information for each location together instead of separate feature classes. Separate classes open the possibility that data may be assigned to wrong locations or may be forgotten and not recorded. Also, by planning the geodatabase beforehand, all fields or attributes collected, can be assigned a range or code to help eliminate data entry errors to help improve the data integrity. These ranges or coded values are Domains. Domains ranges or codes can be applied to a field so only values that fall in that range or assigned code are allowed to be recorded into the feature class. The same domain may be set to multiple fields if those fields have the same data range or codes. Domains can also be associated with all different field types available in a feature class, which include: short integer (short), long integer (long), single precision floating point numbers (float), double precision floating point numbers (double), alphanumeric characters (text), data and time data (date). When assigning the domains, only those that match the field type of the field in question will be available to assign. This will be demonstrated below. As domains are created for the fields, they are saved inside the geodatabase and can be accessed or edited throughout the project. With all the domains set to the fields created in the single feature class, when the database is loaded onto the portable unit, data entry will be faster and more accurate for analysis later.

Using a Geodatabase in Microclimate mapping: What information needs to be collected?

• ·         Temperature
• ·         Dew point
• ·         Wind speed/direction
• ·         Snow depth
• ·         Relative Humidity
• ·         Time
• ·         Notes of the surrounding area  

 

Figure 1: From the geodatabase properties menu, two tabs are displayed. The domains are created here with all descriptions, codes, and ranges to later be assigned to feature class fields. 

Domains: To create new domains for use in feature classes, right click on the geodatabase and select properties. A new window will open having two tabs: general and domains (Figure 1). The domain tab is where you can name and assign parameters for each field you wish to collect. For the information listed above, the following domains were created:

• ·         Temperature – Float, type: range, minimum 0 maximum 99
• ·         Dew point – Float, range, 0-100
• ·         Wind speed/direction – float, range, 0-360
• ·         Snow depth – float, range, 0-36
• ·         Relative Humidity – float, range, 0-100
• ·         Time – short integer, range, 0-2400
• ·         Notes of the surrounding area – Text

Once all the needed domains are created, click OK. The domains will now be listed in the property field when created fields for a new feature class. Only those domains that match the data type for a field will be listed in the menu.     

Figure 2: The feature class properties will display all fields listed in the feature class along with any set parameters such as domains. 

Feature classes: For this project, each spot surveyed for microclimate data are going to be saved as a point feature. Since multiple features can be linked to a single point, it’s best to use a single feature class with multiple fields. Each piece of information listed above will have its own field in the feature class (Figure 2). To create a feature class right click on the file geodatabase you wish to add the data to. Then select new-feature class. A new window will open leading you through the process of creating the new feature class. 

Figure 3: When creating a new feature class in a geodatabase, a new window will open. Follow the prompts to define the projection then at this window the fields will be created. Each field has an assigned data type and domain associated with what is being collected.

You will first name and assign a coordinate system, then proceed to the window that prompts for field names and data types (Figure 3). This is where you will add the field title for each piece of data collected. The data type will depend on the field and can be text or numeric. Here is also where you will assign the domains created before to each field. In the Field properties box, click the area next to “Domain”. This will have a drop down box where you will be able to select the correct domain for each field in the feature class. Once all the fields are created and domains assigned, click finish to setup the feature class.