Digitizing Information
For a more in-depth understanding of the digitization process, see the technical lesson on Digitizing. Digitizing information is the process of manually capturing data from a georeferenced layer file. This is required because this layer file is a raster image, not a vector and none of the information has attributes associated with the data. For example, the position of a regiment at 2 PM cannot be individually referenced, the line representing it is just a series of dots on the image and has no information about the regiment’s position. The feature class file that will be created must be located in a geodatabase. The type of database can be a file geodatabase or a relational geodatabase; for this example, a file geodatabase will be used.
Procedure
1. The geodatabase is created using ArcCatalog. Right click in an empty space and select New. Then select a File Geodatabase (see Figure 1). For this example, a file geodatabase will be used. |
2. After creating the geodatabase (or using an existing one), a feature class file must be created in the geodatabase. To create a new feature class file use ArcCatalog. Right click on the geodatabase and select New and then select Feature Class. Provide a descriptive name for the file using no spaces and a common name in the Alias box (which can use spaces). Then select the Feature Type, for this case a polyline is created. Give the new file a coordinate system; it is suggested that the same projection be used as that of the base layers. The next two windows can use the defaults.
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3. The file structure must be created with the appropriate fields. Typically, on a Civil War battlefield map project, units are digitized at the regimental level, since this was the basic fighting unit used during the Civil War. Many times larger units are referenced by the commander’s name.Items to consider for the file structure
Each field name must have no spaces and the creator must select the type of data. Different Field Properties will be created depending on the data type selected. Add all needed fields and information and then click finish, this will create the feature file. The field (attribute) creation is part of the database file s, additional fields can be added following this process using the methods described in step 4. If no additional fields are required, this section can be skipped.
- State of the regiment
- Regiment Number
- Side, i.e. Union or Confederate
- Type of unit, i.e. infantry, cavalry, artillery
- Unit commander
- Brigade commander
- Division commander
- Corps commander
- Army commander
- Time they occupied the position
- Time they were removed from the position
- Battlefield flag
Each field name must have no spaces and the creator must select the type of data. Different Field Properties will be created depending on the data type selected. Add all needed fields and information and then click finish, this will create the feature file. The field (attribute) creation is part of the database file s, additional fields can be added following this process using the methods described in step 4. If no additional fields are required, this section can be skipped.
5. Once the feature file has been composed the Editor Toolbar is used to digitize the information and provide the appropriate attributes. Make sure the edits are saved as this is not an automatic process. To digitize a regiment’s location at a specific time period, have a georeferenced map showing the troop positions. Turn on the editor, by using the pull down on the on Editor Toolbar. If the editor toolbar is not visible it needs to be selected.
6. Select the file to be edited. Double click on the file to select it for editing. Then select the line feature.
6. Select the file to be edited. Double click on the file to select it for editing. Then select the line feature.