AutoCAD Map 3D 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.