Available with Image Analyst license.
Available with Spatial Analyst license.
Assigning classes after unsupervised classification
After you have performed an unsupervised classification, you need to organize the results into meaningful classes based on your schema. A common practice when classifying an image using unsupervised classification is to specify many more classes than are represented in your class schema. This approach accommodates variability within a specific class. For example, different pitches of a roof display different shades of gray due to differences in illumination, and each shade of gray is represented as a separate class in your output classmap. The purpose of the Assign Classes tool is to assign classes and subclasses in your unsupervised classmap to a class in your schema.
On the top of the Assign Classes pane, your class schema is displayed, and at the bottom of the page there is a table that allows you to assign classes based on the schema.
Follow the steps below to assign the unsupervised classes to a schema class.
- In the top portion of the page, select a class from the schema that you want to assign on the map.
- Click the Assign tool, then select the classes on the classmap that you want to assign to the schema class. As you assign classes, you can see the underlying imagery to verify that the New Class make sense. Press the L key to toggle the transparency of the classified image. Inspect the table to see that Old Class is updated with the class you have assigned. The class color will be updated to reflect the color defined in your schema.
If you toggle off the classmap in the Contents pane so that the source image is displayed, you can click on features in the imagery, such as gray roofs or lawns, which will still reassign the corresponding classes in the classmap.
- Repeat step 2 until all of the classes in the unsupervised classmap have been assigned a class from the schema.