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Transformations in Surveying

This documentation describes the transformation types available in Gemini Terrain and how they are used.

Available Transformation Types

The following transformation types are available in Gemini Terrain:

  • Helmert transformation (2D)

  • Affine transformation

  • Recursive transformation

  • Transformation using SkTrans (Skt2lan1.dll)
    (The Norwegian Mapping Authority will eventually phase out SkTrans with the new PROJ transformation library when their new transformation service meets all customer needs.)

  • Transformation using PROJ

  • Helmert transformation (3D)
    (7 parameter transformation)

Using Transformations

You can transform standard application layers and surveying application layers directly in the drawing. For standard application layers, you can also transform data during import and export.

Coordinate System Information in Files

During data import, Gemini Terrain reads coordinate system information from some file formats such as SOSI, LAS, and GML, while other file formats do not contain this information.

Import Process

When you import data to an existing application layer, the program will check if the application layer has coordinate system information. The application layer's coordinate system information is used as the target system if it exists; otherwise, the project's coordinate system information is used.

Note

If the coordinate system information differs between the application layer and external file, you will be asked to transform data during import. This will always be the case for files that do not contain coordinate system information, such as DWG and KOF.

Tip

If the application layer is empty and the coordinate system information differs, the information in the external file will be used.