The effective organization of project data in shared or related coordinates is essential to effective collaboration across disciplines and good quality project information. BIM Coordinator for AutoCAD® Civil 3D® and Autodesk® Revit® software is a free* technology preview that assists project team members with building and site grids.
Building grids are generally selected based on the layout and shape of the building, usually using the lower left corner of the selected orientation as a reference point. Building grids are established by the lead designer of a project for use by all members of the building design team. This grid ensures that different disciplines' building designs use the same reference for purposes of building analyses, drawing production, and other tasks requiring coordinated building data.
Site grids are generally based on Northing and Easting coordinates. They are usually established for a region; although arbitrary grids can be established for a single project or site. For example, in the UK most sites are related to the Ordinance Survey (OS) grid. Site elevations (levels) are also based on an OS benchmark or other site/project benchmark.
Coordination of building and survey grids
BIM Coordinator for AutoCAD Civil 3D and Revit automates the more error-prone manual steps in the coordination of site and building grids between the AutoCAD and Revit environments. The tool specifies one common XYZ point and its orientation in the XY plane between the two coordinate systems. This reference point defines the relationship between the building and site grid.
There's more information on the Autodesk Labs product webpage.
There's also a nice writeup by Steve Stafford over on his Revit OpEd blog.