FME Form: 2024.2
A custom coordinate system is a Shared Resource that defines one or more coordinate systems that are not included in FME by default.
FME is used in many different countries around the world, and it is also used with a variety of custom datasets within each country. However, sometimes FME’s Coordinate System Gallery doesn't include the coordinate systems that are being used. In these cases, you will have to define the coordinate systems before FME can use them.
Adding a Custom Coordinate System
To add a custom coordinate system, create a new .fme file that defines one, and save it to %USER%\Documents\FME\CoordinateSystems, or a shared folder (defined in Tools > FME Options > Default Paths > Shared FME Folders).
Using the Online Tool
Safe provides an online tool you can use to create a custom coordinate system. You can customize from an existing coordinate system, or create an entirely new one.
Manually Customizing from an Existing Coordinate System
You can manually customize an existing coordinate system to create a new one:
- Open the coordinate system gallery (Tools > Browse Coordinate Systems).
- Select the Coordinate system you are using as a model.
- Click Properties.
- In the properties window of the coordinate system, copy the text under "Coordinate System Parameters", and paste in a text editor.
- Format the definition to conform to the FME coordinate system syntax. For examples, refer to the MyCoordSysDefs.fme file, located in the Reproject folder of your FME install directory.
- Add, remove, and/or edit parameters to customize the coordinate system.
- Save the file as <custom_coordinate_system_name>.fme to %USER%\Documents\FME\CoordinateSystems, or a shared folder (defined in Tools > FME Options > Default Paths > Shared FME Folders).
You must restart FME Workbench before FME can recognize the custom coordinate system.
The custom coordinate system will appear in the columns of the Coordinate System Gallery.
The projection and units of your source data are not predefined within FME, so, to define them, you must add the following lines:
| Coordinate System Definition Lines | Additional Information |
|---|---|
|
COORDINATE_SYSTEM_DEF <coordsysname> \ |
|
|
PROJ <projType> \ |
Table of projection types |
|
UNIT <unitName> \ |
Table of predefined units |
|
(DT_NAME <datumName> | EL_NAME <ellipName>) \ |
Table of predefined datums and predefined ellipsoids. Note that each coordinate system definition must specify either a datum or ellipsoid. |
|
[<parameter> <value>]+ \ |
|
|
[DESC_NM <descriptive_name>] \ |
|
|
[GROUP <group_name>] \ |
Tip Defining a unique
group name allows you to sort coordinate systems by the "Group"
column in the Coordinate System Gallery.
|
|
[QUAD <quadrant>] \ |
Quadrant definition |
|
[SOURCE <source>] \ |
|
|
[ZERO_X <zero_x>] \ |
|
|
[ZERO_Y <zero_y>] \ |
|
This example of a custom coordinate system defines a NAD83-based UTM Zone
12 coordinate system:
COORDINATE_SYSTEM_DEF UTM12N83 \
PROJ TM \
UNIT METER \
DT_NAME NAD83 \
PARM1 -111.0 \
GROUP "Custom Group" \
SCL_RED 0.9996 \
ORG_LAT 0.0 \
X_OFF 500000.0 \
Y_OFF 0.0 \
ZERO_X 0.001 \
ZERO_Y 0.001
Parameter Descriptions
The parameters above are described in Coordinate System Parameters.
Sharing Custom Coordinate Systems
Coordinate systems can be read from user-defined folders (including network shares).
This option is especially useful for groups who work together. For instance, if an entire workgroup uses just a few custom coordinate system definitions, keeping these definitions in one place means that everyone doesn't have to have a copy. Then, whenever any of the definitions are updated, the entire group automatically has access to the new version.
See Shared Directories.
Coordinate Systems Files Reference
coordsys.db
Located directly under the root FME installation folder, this file contains the names and descriptions of all predefined coordinate systems. It is typically a subset of all the definitions that are known to FME. That is, there may be additional systems defined in the coordsys file that are not in coordsys.db because the systems have been deprecated, or for some other reason.
Note Any systems defined in LocalCoordSysDefs.fme, MyCoordSysDefs.fme or as an FME Shared Resource are automatically added to FME and do not need an entry in this file.
LocalCoordSysDefs.fme
To allow sites to add their own coordinate systems, a file of local coordinate system definitions is automatically loaded. This file is called LocalCoordSysDefs.fme.
Located in the Reproject subfolder under the FME installation folder, this file contains overrides to the standard coordinate systems (and related parameters) defined by FME, and is made available to each FME session. It contains a series of COORDINATE_SYSTEM_DEF,DATUM_DEF, ELLIPSOID_DEF, and UNIT_DEF lines that define additional, site-specific coordinate systems.
The built-in definitions for any coordinate system/datum/ellipsoid may be overridden by this file. The structure of LocalCoordSysDefs.fme is the same as MyCoordSysDefs.fme, and its contents can be used as a template for new custom coordinate systems.
Warning You should NOT edit LocalCoordSysDefs.fme because it is overwritten each time FME is installed.
MyCoordSysDefs.fme
Located in the Reproject folder, this file contains custom coordinate system definitions.
Warning Although FME does not overwrite MyCoordSysDefs.fme during installation, it is always good practice to back up this file. FME does overwrite LocalCoordSysDefs.fme and coordsys.db during installation. Although you should not need to edit these files, you should back them up if you did make any changes.