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

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

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

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

View a sample Translation File

Copy

TFFIL         Lantmäteriet    2006-08-24
 Överräkning mellan SYSTEM: 
 SWEREF 99 13 30 Ellh-> SWEREF 99 lat long ellh
/
FSYSTEM SWEREF 99 13 30 Ellh/
HTYP    ELLIPSOID METER/
TSYSTEM SWEREF 99 lat long ellh/
LATLONG DEG/
HTYP    ELLIPSOID METER/
ELLIPSOID GRS 80/
PROJ    GAUSS
G 13 30 0 DEG
0
150000
1
/
STOP /

View a sample Geoid Definition File

Copy

GEOID       SWEN08_RH2000 grid
 Geoidhöjdsmodell för SWEREF 99,
 bilinjär interpolation i grid SWEN08_RH2000.grd, geografiska lat long
 Gridstorlek:    801x376
 lat-min: 54°      long-min: 10°
 lat-max: 70°      long-max: 25°
 dlat:     0°.02   dlong:     0°.04
/
ELLIPSOID       GRS 1980
/
GRIDSYSTEM      SWEREF 99 lat long
/
HSYSTEM         RH 2000
/
GRIDFIL         SWEN08_RH2000.grd
/

GEOID       SWEN08_RH70 grid
 Geoidhöjdsmodell för SWEREF 99,
 bilinjär interpolation i grid SWEN08_RH70.grd, geografiska lat long
 Gridstorlek:    801x376
 lat-min: 54°      long-min: 10°
 lat-max: 70°      long-max: 25°
 dlat:     0°.02   dlong:     0°.04
/
ELLIPSOID       GRS 1980
/
GRIDSYSTEM      SWEREF 99 lat long
/
HSYSTEM         RH 70
/
GRIDFIL         SWEN08_RH70.GRD
/

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.

Coordinate System Support and Reprojection

Coordinate systems generally have a name and a definition, and the syntax of that definition can vary greatly between both spatial data formats and other coordinate system libraries. Custom and local coordinate systems can also be defined in FME, further complicating matters. For in-depth information, see the Working With Coordinate Systems documentation.

Reprojections are generally done with the FME Reprojection Engine, which is based on the CS-Map coordinate system library. This default can be overridden on a per-workspace basis, using the Workspace Parameters > Translation > Reprojection Engine parameter, and set to Esri. Where appropriate, FME will use the Esri Reprojection Engine if it is selected there, with or without an Esri product being installed.

Coordinate System Support

These transformers perform various coordinate system-related tasks, but do not reproject the data.

CoordinateSystemDescriptionConverter	Looks up coordinate system names and definitions between FME’s internal format and common third-party and open source representations, storing the results as an attribute.
CoordinateSystemExtractor	Retrieves the name of the feature's assigned FME coordinate system into an attribute.
CoordinateSystemRemover	Removes the coordinate system from features, without modifying geometry or coordinates.
CoordinateSystemSetter	Assigns a specified coordinate system to features, without modifying geometry or coordinates.
LocalCoordinateSystemSetter	Assigns a specified local coordinate system to features, without modifying geometry or coordinates.

Coordinate System Reprojection

Different coordinate system libraries (engines) not only contain coordinate system definitions, they also have unique reprojection algorithms. FME’s generic reprojection transformers, in the first table below, default to using the FME (CS-Map) library.

A selection of other libraries is also available, some of which are specific to certain areas of the world or software platforms.

Inherent reprojections, as in a workspace with different input and output coordinate systems selected, default to using the FME (CS-Map) library.

If you are reprojecting explicitly with a transformer in the workspace, using library-specific transformers is recommended. In the case of CsmapReprojector versus the Reprojector (with default engine), the library may be identical, but the CSMapReprojector handles vertical coordinate calculations whereas the Reprojector does not.

Generic Reprojection Transformers

		Library
AttributeReprojector	Reprojects x and y coordinates stored as attributes from one coordinate system to another.	FME (default) or Esri
CommonLocalReprojector	Reprojects one or more features to a local coordinate system centered on the bounding box containing all features.	FME (default) or Esri
ReprojectAngleCalculator	Converts a given angle from one coordinate system to another.	FME (default) or Esri
ReprojectLengthCalculator	Converts a given length from one coordinate system to another.	FME (default) or Esri
Reprojector	Reprojects feature x and y coordinates from one coordinate system to another.	FME (default) or Esri

Library-Specific Reprojection Transformers (Recommended)

		Library (External Links)
CsmapAttributeReprojector	Reprojects x, y, and optionally z coordinates stored as attributes from one coordinate system to another using the CS-MAP library.	CS-Map
CsmapReprojector	Reprojects feature x, y, and optionally z coordinates from one coordinate system to another using the CS-Map library.	CS-Map
EsriReprojector	Reprojects feature coordinates from one coordinate system to another using the Esri reprojection library.	Esri
GridInQuestIIReprojector Great Britain Northern Ireland Republic of Ireland	Reprojects feature coordinates from one coordinate system to another using the Grid InQuestII engine from Ordnance Survey, for use in Great Britain, Ireland, and Northern Ireland.	Grid InQuestII
GtransAttributeReprojector Sweden	Reprojects coordinates stored as attributes from one coordinate system to another using the Gtrans reprojection engine from the National Land Survey of Sweden (Lantmäteriet).	Gtrans
GtransReprojector Sweden	Reprojects feature coordinates from one coordinate system to another using the Gtrans reprojection engine from the National Land Survey of Sweden (Lantmäteriet).	Gtrans
PROJAttributeReprojector	Reprojects coordinates stored as attributes from one coordinate system to another using the PROJ library.	PROJ
PROJReprojector	Reprojects feature coordinates from one coordinate system to another using the PROJ library.	PROJ
ReframeReprojector Switzerland	Reprojects feature coordinates from one coordinate system to another in Switzerland, using the Reframe library from the Federal Office of Topography (swisstopo).	REFRAME

Configuration

Input Ports

Output Ports

Parameters

Raster

Reverse Translation File

If reprojecting rasters, the inverse Translation File must also be provided. Enter the path and filename.

Files may be selected from the Gtrans Translation File gallery via the ellipsis button.

Interpolation Type

Select a method for interpolating reprojected cell values:

Nearest Neighbor	The simplest and fastest method. Values are copied from the nearest cell.
Bilinear	Calculates a weighted average, adjusted for distance, from the four (4) nearest cells.
Bicubic	Calculates a weighted average, adjusted for distance, from the sixteen (16) nearest cells.
Average 4	Calculates a simple average from the four (4) nearest cells. Similar to Bilinear and is useful for numeric rasters such as DEMs.
Average 16	Calculates a simple average from the sixteen (16) nearest cells. Similar to Bicubic and is useful for numeric rasters such as DEMs.

Cell Size

Select a method for resizing cells:

Stretch Cells	The cell size of the raster will be adjusted to maintain the same number of rows and columns in the reprojected raster as there were in the input raster.
Square Cells	The number of rows and columns as well as the spacing will be changed to maintain approximately the same cell ground area and form square cells where the horizontal and vertical cell sizes are equal.
Preserve Cells	Like Square Cells, this option will change both the number of rows and columns and the spacing to maintain cell ground area, but will also try to preserve the original cell aspect ratio, taking into account any warping caused by the reprojection.

Tolerance (cells)

Sets the tolerance, in cells, for approximating reprojected cell locations.

Using the default value of 0.0, every cell will be reprojected.

If a value greater than 0.0 is specified, some cell locations will be approximated. The difference between an approximated cell location and the true cell location should be at most the tolerance value.

For example, if a value of 0.5 is specified, each approximated cell location should be maximum one-half of a pixel away from its true location. Increasing the Tolerance value may improve performance.

Editing Transformer Parameters

Transformer parameters can be set by directly entering values, using expressions, or referencing other elements in the workspace such as attribute values or user parameters. Various editors and context menus are available to assist. To see what is available, click beside the applicable parameter.

How to Set Parameter Values

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.

Using the Text Editor

The Text Editor provides a convenient way to construct text strings (including regular expressions) from various data sources, such as attributes, parameters, and constants, where the result is used directly inside a parameter.

Text Editor

Using the Arithmetic Editor

The Arithmetic Editor provides a convenient way to construct math expressions from various data sources, such as attributes, parameters, and feature functions, where the result is used directly inside a parameter.

Arithmetic Editor

Conditional Values

Set values depending on one or more test conditions that either pass or fail.

Parameter Condition Definition Dialog

Content

Expressions and strings can include a number of functions, characters, parameters, and more.

When setting values - whether entered directly in a parameter or constructed using one of the editors - strings and expressions containing String, Math, Date/Time or FME Feature Functions will have those functions evaluated. Therefore, the names of these functions (in the form @<function_name>) should not be used as literal string values.

Content Types

String Functions	These functions manipulate and format strings.
Special Characters	A set of control characters is available in the Text Editor.
Math Functions	Math functions are available in both editors.
Date/Time Functions	Date and time functions are available in the Text Editor.
Math Operators	These operators are available in the Arithmetic Editor.
FME Feature Functions	These return primarily feature-specific values.
FME Parameters	FME and workspace-specific parameters may be used.
Creating and Modifying User Parameters	Create your own editable parameters.

Dialog Options - Tables

Table Tools

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

Row Reordering

Enabled once you have clicked on a row item. Choices include:

Add a row
Remove a row
Move current row up one
Move current row down one
Move current row to top
Move current row to bottom

Cut, Copy, and Paste

Enabled once you have clicked on a row item. Choices include:

Cut a row - delete and copy to clipboard
Copy a row to the clipboard
Paste a row from the clipboard

Cut, copy, and paste may be used within a transformer, or between transformers.

Filter

Start typing a string, and the matrix will only display rows matching those characters. Searches all columns. This only affects the display of attributes within the transformer - it does not alter which attributes are output.

Import

Import populates the table with a set of new attributes read from a dataset. Specific application varies between transformers.

Reset/Refresh

Generally resets the table to its initial state, and may provide additional options to remove invalid entries. Behavior varies between transformers.

Note: Not all tools are available in all transformers.

For more information, see Transformer Parameter Menu Options.

Reference

Processing Behavior	Feature-Based
Feature Holding	No
Dependencies	Gtrans software and Translation Files, included with FME.
Operating System Restrictions	Windows only.
Aliases
History

FME Community

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

Keywords: SWEREF99 "National Land Survey of Sweden" Sweden