FME Transformers: 2024.2
Categories and Related Transformers
Related Transformers
LocalCoordinateSystemSetter
Reprojector
Reprojects one or more features to a local coordinate system centered on the bounding box containing all features.
Typical Uses
- Reprojecting multiple features into the same local coordinate system
How does it work?
The CommonLocalReprojector receives features and calculates their cumulative bounding box, then reprojects the features to a local coordinate system, centered on that box, with ground units in meters. The center of the data is used as the origin point to minimize and equalize distortion in all directions.
The Projection Type may be either Equidistant (AZMED) or Equal Area (ASMEA).
Reprojector vs. CommonLocalReprojector
The Reprojector can also reproject features to local coordinate systems, however, each feature is handled individually and receives its own coordinate system based on its bounding box. An example using neighborhood polygons is shown below (A). Each feature’s origin is at its center, and so they appear stacked on top of each other.
The CommonLocalReprojector creates a single local coordinate system that spans all of the input features, and applies it to all of them (B).
Z Values
Height is not considered so areas or distances are best preserved for geometry at an ellipsoid height of 0 meters. Despite height not affecting the coordinate system that will be generated, Z values may undergo a unit shift or geocentric to ellipsoid height conversion if a Vertical Handling mode of Heights are relative to the ellipsoid or geocentric is chosen.
Examples
Example: Reprojecting multiple features to a common local coordinate system
In this example, we have a set of neighborhood polygons, in a UTM coordinate system. Note that the extents are appropriate coordinates.
We want to reproject these polygons to a single common local coordinate system.
The features are routed into a CommonLocalReprojector.
In the parameters dialog, we set Projection Type to Equidistant (AZMED), and leave Vertical Handling as its default, Ignore heights and leave them unchanged.
The features are output to a local coordinate system based on the bounding box of all input features.
Usage Notes
- Rasters may only be reprojected in 2D (that is, with Vertical Handling set to Ignore heights and leave them unchanged).
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.
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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. |
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Retrieves the name of the feature's assigned FME coordinate system into an attribute. |
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Removes the coordinate system from features, without modifying geometry or coordinates. |
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Assigns a specified coordinate system to features, without modifying geometry or coordinates. |
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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
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Library |
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Reprojects x and y coordinates stored as attributes from one coordinate system to another. |
FME (default) or Esri |
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Reprojects one or more features to a local coordinate system centered on the bounding box containing all features. |
FME (default) or Esri |
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Converts a given angle from one coordinate system to another. |
FME (default) or Esri |
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Converts a given length from one coordinate system to another. |
FME (default) or Esri |
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Reprojects feature x and y coordinates from one coordinate system to another. |
FME (default) or Esri |
Library-Specific Reprojection Transformers (Recommended)
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Library (External Links) |
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Reprojects x, y, and optionally z coordinates stored as attributes from one coordinate system to another using the CS-MAP library. |
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Reprojects feature x, y, and optionally z coordinates from one coordinate system to another using the CS-Map library. |
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Reprojects feature coordinates from one coordinate system to another using the Esri reprojection library. |
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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. |
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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). |
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Sweden |
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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Reprojects coordinates stored as attributes from one coordinate system to another using the PROJ library. |
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Reprojects feature coordinates from one coordinate system to another using the PROJ library. |
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Switzerland |
Reprojects feature coordinates from one coordinate system to another in Switzerland, using the Reframe library from the Federal Office of Topography (swisstopo). |
Configuration
Input Ports
Input
This transformer accepts any feature.
Output Ports
Output
Features reprojected to a new local coordinate system as specified in parameters.
Parameters
Group Processing (Optional)
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Group By |
If blank, all features will be reprojected to the same local coordinate system. If attributes are specified, each group of features will be reprojected to a local coordinate system centered on that group. |
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Complete Groups |
Select the point in processing at which groups are processed:
Considerations for Using Group By
There are two typical reasons for using When Group Changes (Advanced) . The first is incoming data that is intended to be processed in groups (and is already so ordered). In this case, the structure dictates Group By usage - not performance considerations. The second possible reason is potential performance gains. Performance gains are most likely when the data is already sorted (or read using a SQL ORDER BY statement) since less work is required of FME. If the data needs ordering, it can be sorted in the workspace (though the added processing overhead may negate any gains). Sorting becomes more difficult according to the number of data streams. Multiple streams of data could be almost impossible to sort into the correct order, since all features matching a Group By value need to arrive before any features (of any feature type or dataset) belonging to the next group. In this case, using Group By with When All Features Received may be the equivalent and simpler approach. Note Multiple feature types and features from multiple datasets will not generally naturally occur in the correct order.
As with many scenarios, testing different approaches in your workspace with your data is the only definitive way to identify performance gains. |
General
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Projection Type |
Select a Projection Type based on whether preservation of distances or areas is more important. Choices include:
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Vertical Handling |
Select a method for Z value handling:
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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.
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.
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
| These functions manipulate and format strings. | |
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Special Characters |
A set of control characters is available in the Text Editor. |
| Math functions are available in both editors. | |
| Date/Time Functions | Date and time functions are available in the Text Editor. |
| These operators are available in the Arithmetic Editor. | |
| These return primarily feature-specific values. | |
| 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.
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Row Reordering
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Enabled once you have clicked on a row item. Choices include:
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Cut, Copy, and Paste
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Enabled once you have clicked on a row item. Choices include:
Cut, copy, and paste may be used within a transformer, or between transformers. |
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Filter
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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. |
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Import
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Import populates the table with a set of new attributes read from a dataset. Specific application varies between transformers. |
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Reset/Refresh
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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
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Processing Behavior |
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Feature Holding |
Yes |
| Dependencies | None |
| Aliases | |
| History |
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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.