MicroStation uses the concept of a Geodetic data catalog to determine the location and file names of files to be used for a specific grid shift calculation. For example, the data files used to convert NAD27 to NAD83 and vice versa must be individually listed in a data catalog file. While this introduces some inconveniences, it solves several problems such as:

1. case sensitive file names
2. multiple copies of large data files
3. controlling file precedence
4. supporting different datum conversions covering the same geography.

The remainder of this section is devoted to describing data catalog files.