Overview of Grid Data Files and Datum Shift Issues
Concept Procedure

When converting between certain coordinate systems in North America, France, Australia, and New Zealand, AutoCAD Map 3D uses grid-based data files called grid data files to obtain datum shift information.

For the United States, France, Australia, and New Zealand geography, the grid data files are in the public domain and are distributed with AutoCAD Map 3D. The grid data files which cover Canadian geography are not in the public domain and must be obtained from the proper authorities in Canada.

AutoCAD Map 3D uses Grid Data Catalog (GDC) files to determine the order in which grid data files are used in areas of overlap when converting from one datum to another.

See Also