A precise physical survey of a site - boundaries, existing levels, utilities, existing structures - carried out by a licensed surveyor and used as the accurate ground-truth base a model is built on top of. A site survey is typically imported as a linked drawing or point file and tied to the project's shared coordinates, anchoring everything modeled afterward to the real world.

Skipping or rushing a proper site survey is one of the most common sources of expensive downstream problems: a building modeled against inaccurate site data can end up with the wrong finished floor level, misaligned property boundaries, or a design that does not actually fit the real topography once construction starts.