Each stratigraphic layer spans a vertical range, and depthTop marks where that range starts — the upper boundary of the layer. Paired with depthBottom, it defines exactly how thick the layer is and where it sits in the unit's profile. Both depth fields are required, so every layer has a defined extent. Stored as a decimal, depthTop preserves the precision archaeologists use when measuring layer boundaries, and it lets you correlate an artifact's depthCmbd with the layer it belongs to.
Technical section
Data model, API, and internals — visible to developers.