SA_STRAT is the department’s computerised database of stratigraphic units, comprising named formal stratigraphic units and unnamed mapping units. All current stratigraphic units are tagged with a GIS Search Code unique to each unit and used consistently across the State and at all map scales. The code is constructed in a hierarchical manner, based on age, followed by stratigraphic rank in descending order from left to right. The map symbol is a shortened form of the GIS Search Code, and is also unique State-wide for each stratigraphic unit. Although simpler, the Map Symbol is not as strictly hierarchical because of the variable guidelines used for simplification. For the great majority of inquiries, however, use of the Map Symbol is very reliable; for rigorous hierarchical searches, the GIS Search Code is better.