When you bring objects and features into the current drawing, AutoCAD Map 3D checks whether the coordinate system assigned to the object or feature matches that of the current drawing. If it does not, AutoCAD Map 3D transforms the object or feature to the current drawing’s coordinate system. If you edit and save the object or feature back to its source, AutoCAD Map 3D transforms it back to its original coordinate system.
You cannot assign a coordinate system to the current drawing if it contains any objects that have been queried from source drawings. If you are using the Canadian National Transformation, you must copy the data files to the Autodesk shared coordinate system directory.
Select the attached drawings, then enter the code for these drawings. Click Select Coordinate System to select from a list of available coordinate systems. To assign a different code to other source drawings, use this command again.