Creating new donut holes and island polygons
Sometimes you need to create a polygon with a hole in it or even a polygon with both a hole and an interior polygon. To create these kinds of polygons, you need to create a multipart feature.
Click Options and disable 'include island polygons' to reduce the complexity of the output.
Click on the region grow tool in the main window.
Click the tool in the middle of the lake - ERDAS should outline the lake.
Activate the region by clicking in the
Name the region.
Islands, or island polygons are common in spatial data, for example an island may represent features such as enclosed areas of water such as lakes, or parks within urban areas.
Join: The relating of two or more tables in a relational database on the basis of a common item or field.
See also: Mapping, Boundary, Digitize, Feature, Attributes