Each project site is configured with its geographical area extent, and optional sub-areas within the overall extent. The overall area is normally a single polygon (provided as a GIS dataset) but can be multiple separate areas, for example for a county that includes an island.

Having sub-areas can be useful in helping to allocate work between different officers, and for monitoring progress and backlogs. The sub-areas are usually some administrative unit, such as Districts in a two-tier context, or various types of local authority when a Local Heritage List is being prepared collaboratively, or some internal sub-division in other contexts (e.g. electoral districts).

The sub-areas must cover the whole of the main area (no gaps!).