Overlay Key

Overlay Keys establish a link between Attributes that an Overlay's calculation model requires and Attributes the users and geo-sources supplied. For example, Water Overlays require an attribute to identify Weirs by their Weir height. Let's say the Weir data is often supplied by a user, where the Weir height is described by the attribute HEIGHT_OBJ. The Overlay Weir Height Key can be set to HEIGHT_OBJ. This way, when the Water Overlay wants to first identify Buildings as Weirs and secondly obtain their Weir Height value, they can use the attribute HEIGHT_OBJ, which they had stored for the WEIR_HEIGHT key.

The Keys an Overlay's calculation model uses and their configured values can be found under the tab Keys in the Template:Right panel.