Overlays can be thought of as transparent sheets on which any graphical data is placed. The term Overlay is used to describe a view of a dataset. A dataset can be:
- a read-only graphical file (e.g. an NTF, DXF, or BMP file)
- a user dataset (BDS file)
- a database (IDB file)
- stored within the SIS Workspace Definition (SWD) (internal dataset or index dataset)
- data retrieved from a spatial database, e.g. Oracle, PostGIS, Microsoft SQL Server 2008.
- an internal binary geometry dataset
TIP: For a full list of datasets that can be included as overlays, see also Dataset Formats.