Feature Depth Bottom

The depthBottom of a Feature is the measured depth at which the feature bottoms out, the floor of a PIT or POSTHOLE or the base of a BURIAL. Together with depthTop it defines how deep the feature is and therefore how much excavation it represents. The difference between the two values gives the feature's thickness, useful for estimating fill volume and for judging whether a feature is shallow and ephemeral or deep and substantial. Like its companion, depthBottom is optional and is recorded once excavation reaches the base of the feature; while a feature is only PARTIALLY_EXCAVATED, this value may still be provisional.