When more than one team needs to coordinate models with each other (critical when clash detecting), then they need to use shared coordinates. The accepted workflow is for the Architect to link in the site drawing and then acquiring the coordinates. When the architect then shared their model with the rest of the team, they can link it in by shared coordinates, after which they may link in any of the files at will (perfectly coordinated).
Often a site design is based on a Surveyor General’s diagram, but there is no topographical information available. The main boundary points are indicated in linear longitudinal and latitudinal measurements and are referenced to some beacon which indicates the origin. This is necessary as the planar approximation is a result of a transformation from a geoidal shape to a plane.
Typically a Surveyor is then tasked with determining the relevant topography. This may be done by individual point measurement, or through some more efficient processes like laser scanning or photogrammetry.
Identifying individual points to accurately place the Revit topography is difficult, and often the site may be very far from the origin. For this reason, the points file is translated to close to the Revit Project Internal origin. This video shows how to do that using Excel and a little bit of construction in AutoCAD. It also demonstrates that the topography is perfectly coordinated with the CAD File.
