AutoCAD Map 3D automatically converts drawings from one coordinate system to another using a hard-coded library of grid-based transformations. Use Use the Geodetic Transformation Path Definition dialog box ( from within the Coordinate System Library) or the Create Geodetic Path Transformation wizard to define your own transformation paths.
Available geodetic transformation paths are listed on the left, along with their source and target datums. Select a path and click Add or Add Inversed.
As you add transformations to the path, the list of available geodetic transformations is reduced to only show geodetic transformations where the source datum of the transformation is the (current) target datum of the transformation path.
Enter a value to indicate the loss of accuracy (in meters) that applying the selected transformation might bring to target coordinates. This value is used to determine whether the accuracy of one coordinate operation is more accurate than another.
Values are positive numbers and typically range from zero to 100. For projective calculations, which are considered exact by definition, the value is 0. The following table shows some recommended values.
| Method | Recommended Value |
|---|---|
| Molodensky Geocentric Translation | 10 |
| Abridged Molodensky four-parameter transformation | 10 |
| Bursa Wolf 6-paramete transformation | 5 |
| 7-parameter Molodensky-Badekas transformation with multiple regression | 3 |
| Grid File interpolation [All formats] | 5 |