Geodetic Transformation Definition

AutoCAD Map 3D toolset automatically converts drawings from one coordinate system to another using a hard-coded library of grid-based transformations. Use the Geodetic Transformation Definition dialog box ( from within the Coordinate System Library) or the Create Geodetic Transformation wizard to define your own transformations based either on a grid file or on parameters you specify.

Code
Enter a code for this geodetic transformation. The code will be used in lists of geodetic transformations.
Description
Enter a description that can help you remember any salient details of the transformation.
Datum
Displays the source and target datum for the selected geodetic transformation.
Data Conversion Method
Specify whether to use an analytical formula or an interpolation.
Geocentric Translation
Enter the following:
  • Delta X (meters): -5,000 to +5,000
  • Delta Y (meters): -5,000 to +5,000
  • Delta Z (meters): -5,000 to +5,000
Axis Rotation of Arc
Enter the following:
  • X-axis (seconds) : -100 to +100
  • Y-axis (seconds) : -100 to +100
  • Z-axis (seconds) : -100 to +100
Axis Translation
Enter the following:
  • X-axis (meters) : -100,000 to +100,000
  • Y-axis (meters) : -100,000 to +100,000
  • Z-axis (meters) : -100,000 to +100,000
Scale
Enter the following:
  • Scale (parts per million): -100 to +100
Grid File Format
Select from the following:
  • Canadian NTv1
  • Canadian NTv2
  • US NADCON las/los pair
  • French RGF93 Text File
  • Japanese Par File
  • ATS77 Transform

Once you have selected a format, the grid files matching that format are displayed. Select the ones you want and click +.

Inverse Transformation
Select this option to automatically generate a formula to get back to the first coordinate system from given coordinates in the second, using the specified grid files.
Fallback Transformation
Select this option in case the method you create does not work (for example, if the grid files are not found at the time of transformation. Click an existing analytical geodetic transformation in the Coordinate System Library.
Multiple Regression Transformation
Indicates that the selected geodetic transformation uses multiple regression transformation, and therefore cannot be copied and edited.