GtransReprojector

Reprojects feature coordinates from one coordinate system to another using the Gtrans reprojection engine from the National Land Survey of Sweden (Lantmäteriet).

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Typical Uses

  • Reprojecting features when explicitly using the Gtrans engine is desired
  • Reprojecting features in select local coordinate systems not supported elsewhere

How does it work?

The GtransReprojector receives raster, vector, or point cloud features and reprojects their coordinates from one coordinate system to another, using the Gtrans engine and translation files.

Gtrans is widely used for coordinate transformation within Sweden as it is officially recommended, translates between numerous local coordinate systems, and supports rubbersheeting transformations.

The transformation is configured by selecting a Gtrans Translation File appropriate for the Source and Destination Coordinate System. For raster features, the Reverse Translation File must be identified as well.

Output features’ coordinate system will show as Unknown, as these features no longer have an FME coordinate system tag. If the output coordinate system is known to have an exact match in FME’s coordinate system library, it can be tagged manually with a CoordinateSystemSetter.

Translation Files

A selection of Gtrans Translation Files are provided with FME.

Only reprojections defined here or with a user-provided Gtrans Translation File (see below) may be performed with this transformer.

File Type

Description

Location

*.tf, *.tfi

Translation File - a text file containing parameters defining a reprojection from one coordinate system to another.

  • *.tf - forward reprojection
  • *.tfi - inverse reprojection of the tf file with the same name.

[FME Install Directory]\Reproject\Gtrans\Sys

*.tr1, *.tr2

Triangulation File - a binary file used for the interpolation of residuals.

  • *.tr1 - forward
  • *.rf2 - inverse of the *.tr1 file with the same name.

[FME Install Directory]\Reproject\Gtrans\Sys

Each *.tf/*.tfi file corresponds to a line item in the Gtrans Translation Files library accessed in the parameters dialog.

Note that when using the Filter option, FME searches the file names of the *.tf/*.tfi files - not the Source and Destination Coordinate Systems.

Geoid Files

When reprojecting between geoids, this transformer needs additional resource files.

File

Description

Location

geoid.def

Geoid Definition File - a text file containing parameters describing geoids. A default version is provided with FME.

User-provided geoids may also be used - see below.

[FME Install Directory]\Reproject\Gtrans\Sys

*.grd

Binary Grid files for specific geoids.

[FME Install Directory]\Reproject\Gtrans\Sys

Gtrans User Data

Users may provide their own transformations and definitions by placing the appropriate files as directed:

File(s)

Description

Location

*.tf, *.tfi

Translation File - a text file containing parameters defining a reprojection from one coordinate system to another.

  • *.tf - forward reprojection
  • *.tfi - inverse reprojection of the tf file with the same name.

The Translation File should reference the correct geoid.def and any required *.bin files.

User-defined translations are placed in the same location as the provided Translation Files.

[FME Install Directory]\Reproject\Gtrans\Arkiv

geoid.def

Geoid Definition File - a text file containing parameters describing geoids. A default version is provided with FME.

The user version of this file is placed in a different location than the default geoid.def provided with FME.

[FME Install Directory]\Reproject\Gtrans\Arkiv

*.bin

Binary Grid files for specific geoids.

[FME Install Directory]\Reproject\Gtrans\Arkiv

Rasters

Additional parameters are available for raster features, specifying how the reprojected cells are to be interpolated. Both the forward and Reverse Translation Files for the reprojection must be provided.

This transformer is not affected by raster band and palette selection.

Examples

Usage Notes

  • FME has a Workspace Parameter, Reprojection Engine, that may be set to either FME (CS-Map) or Esri. This transformer will override this parameter setting.
  • The Reprojector provides similar functionality, and will use the default library (CS-Map or Esri) set in FME. It supports some Swedish coordinate systems, but will not use the Gtrans definitions or reprojection engine.
  • To reproject coordinates stored as attribute values, consider using the GtransAttributeReprojector.

Working With Coordinate System Transformers

FME inherently supports coordinate system transformations and reprojections.

Configuration

Input Ports

Output Ports

Parameters

Editing Transformer Parameters

Using a set of menu options, transformer parameters can be assigned by referencing other elements in the workspace. More advanced functions, such as an advanced editor and an arithmetic editor, are also available in some transformers. To access a menu of these options, click beside the applicable parameter. For more information, see Transformer Parameter Menu Options.

Defining Values

There are several ways to define a value for use in a Transformer. The simplest is to simply type in a value or string, which can include functions of various types such as attribute references, math and string functions, and workspace parameters. There are a number of tools and shortcuts that can assist in constructing values, generally available from the drop-down context menu adjacent to the value field.

Dialog Options - Tables

Transformers with table-style parameters have additional tools for populating and manipulating values.

Reference

Processing Behavior

Feature-Based

Feature Holding

No

Dependencies Gtrans software and Translation Files, included with FME.

Operating System Restrictions

Windows only.

Aliases  
History  

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Examples may contain information licensed under the Open Government Licence – Vancouver and/or the Open Government Licence – Canada.

Example contains data © OpenStreetMap contributors.

Keywords: SWEREF99 "National Land Survey of Sweden" Sweden