This topic provides some guidance on choosing ROI types and drawing ROIs as part of the labeling process for ENVI Deep Learning. First, decide what type of ROI would be most suitable for the feature you want to label.

Choose point or polyline ROIs if you want to count and locate features, as opposed to defining their boundaries and shapes (referred to as segmentation). Points and polylines are easier and faster to draw than polygons, and they are the best option for labeling features that have similar sizes and shapes. Points can be used to identify individual features such as cars or trees. Polylines can be used to identify linear features such as roads or rivers. With points and polylines, you can "grow" the size of the feature to reflect its real-world size using the Solid Distance parameter later in training. See the Solid Distance description for details.

Polygon ROIs are the best option for labeling features that have irregular sizes and shapes. Use polygons when you want to define the boundaries and shapes of features. However, drawing polygons can take much longer than using points or polylines.

For point ROIs, click in the Image window to add points within the centers of objects. Then right-click and select Accept Points. The following image shows an example of point ROIs drawn over residential driveways:

For polylines or polygons, click in the Image window to add line segments. To complete each polyline after drawing it, select Complete and Accept Polyline. To complete each polygon after drawing it, select Complete and Accept Polygon. The following images show some examples:

Draw ROIs on every instance of a feature in your training rasters. Try to include a variety of shapes, colors, and textures of the feature you are interested in. This will contribute to better accuracy in the final classification.

In some cases, you may want to create a label raster that consists entirely of background pixels with no feature pixels. To do this, right-click on the input raster in the Layer Manager and select New Region of Interest. In the Region of Interest (ROI) Tool, accept the default ROI Name of ROI #1. This creates an empty ROI. Then select the ROI in the Input ROI field of the Build Label Raster from ROI tool.