PROJAttributeReprojector

Grid shift files can be stored locally if preferred.

The PROJ website’s Download page includes grids, in archives named proj-data*.* To use them:

1. Download a proj-data archive. The Current Release version is generally appropriate. Do not use the older proj-datumgrid*.* archives.

2. Extract the archive’s contents to the ProjData directory (or a subdirectory thereof) in the FME user directory, per operating system:
   ~/.fme/ProjData on Linux
   ~/Library/Application Support/FME/ProjData on macOS
   Documents/FME/ProjData on Windows

Grids added in this way will be considered before online grids (if enabled). They will also be considered first in order of preference, unless an absolute or relative path or URL is specified in the transformation definition.

FME can also access PROJ grids online at cdn.proj.org.

Online access may be enabled or disabled via the FME Form menu - Tools > FME Options > Coordinate Systems:

PROJ will look for an appropriate grid, which can be accessed in a number of places. The search order is:

• If the transformation definition contains an absolute or relative path to a grid shift file, only that file will be considered. If it cannot be found, processing terminates with an error.

• If the transformation definition contains a URL for grid shift file (that is, starting with http:// or https://), PROJ will attempt to download the file. If it cannot be found, processing terminates with an error.

• If the transformation definition contains only a grid file name with no path or URL, PROJ will search in this order:

  1. FME configured search paths:

     • - Reproject directory in the installation directory

     • - ProjData directory in the FME user directory

  2. The user-writable directory, such as:

     • AppData/Local/proj on Windows

     • ~/.local/share/proj on Linux
     • ~/Library/Application Support/proj on macOS

  3. The list of directories specified in the PROJ_LIB environment variable.

  4. The directory the FME workspace file is stored in (the working directory for a translation).

  5. If the file name is not found, PROJ will search for known aliases in the same order:

     • eg: ca_nrc_ntv2_0.tif has ntv2_0.gsb as an alias

  6. If no known aliases are found, and Online Grids is enabled, PROJ will attempt to download the grid from the specified CDN Endpoint.

  7. If networking fails, then PROJ’s options are exhausted and an error is returned.

In this example, we start with a CSV file of Historic Sites. It has no geometry, but it does contain coordinates for the sites, with a UTM Zone 10 NAD27 coordinate system. We want to reproject this to NAD83, using PROJ.

The features are routed into a PROJAttributeReprojector.

In the parameters dialog, Transformation Type is set to Manual Transformation.

The required PROJ pipeline string is entered, which references both the source and destination coordinate system definitions and the desired grid shift file.

Both the X and Y Attributes containing the coordinates are identified.

The new coordinates are calculated using the PROJ library, and replace the existing attribute values. The transformer does not create geometry, it only supplies values.

The previous example could also be performed using Well-Known Text (WKT2) to describe the transformation.

WKT2 Transformation Description

CONCATENATEDOPERATION["Inverse of UTM zone 10N + NAD27 to NAD83 (4) + UTM zone 10N",
    SOURCECRS[
        PROJCRS["NAD27 / UTM zone 10N",
            BASEGEOGCRS["NAD27",
                DATUM["North American Datum 1927",
                    ELLIPSOID["Clarke 1866",6378206.4,294.978698213898,
                        LENGTHUNIT["metre",1]]],
                PRIMEM["Greenwich",0,
                    ANGLEUNIT["degree",0.0174532925199433]],
                ID["EPSG",4267]],
            CONVERSION["UTM zone 10N",
                METHOD["Transverse Mercator",
                    ID["EPSG",9807]],
                PARAMETER["Latitude of natural origin",0,
                    ANGLEUNIT["degree",0.0174532925199433],
                    ID["EPSG",8801]],
                PARAMETER["Longitude of natural origin",-123,
                    ANGLEUNIT["degree",0.0174532925199433],
                    ID["EPSG",8802]],
                PARAMETER["Scale factor at natural origin",0.9996,
                    SCALEUNIT["unity",1],
                    ID["EPSG",8805]],
                PARAMETER["False easting",500000,
                    LENGTHUNIT["metre",1],
                    ID["EPSG",8806]],
                PARAMETER["False northing",0,
                    LENGTHUNIT["metre",1],
                    ID["EPSG",8807]]],
            CS[Cartesian,2],
                AXIS["(E)",east,
                    ORDER[1],
                    LENGTHUNIT["metre",1]],
                AXIS["(N)",north,
                    ORDER[2],
                    LENGTHUNIT["metre",1]],
            ID["EPSG",26710]]],
    TARGETCRS[
        PROJCRS["NAD83 / UTM zone 10N",
            BASEGEOGCRS["NAD83",
                DATUM["North American Datum 1983",
                    ELLIPSOID["GRS 1980",6378137,298.257222101,
                        LENGTHUNIT["metre",1]]],
                PRIMEM["Greenwich",0,
                    ANGLEUNIT["degree",0.0174532925199433]],
                ID["EPSG",4269]],
            CONVERSION["UTM zone 10N",
                METHOD["Transverse Mercator",
                    ID["EPSG",9807]],
                PARAMETER["Latitude of natural origin",0,
                    ANGLEUNIT["degree",0.0174532925199433],
                    ID["EPSG",8801]],
                PARAMETER["Longitude of natural origin",-123,
                    ANGLEUNIT["degree",0.0174532925199433],
                    ID["EPSG",8802]],
                PARAMETER["Scale factor at natural origin",0.9996,
                    SCALEUNIT["unity",1],
                    ID["EPSG",8805]],
                PARAMETER["False easting",500000,
                    LENGTHUNIT["metre",1],
                    ID["EPSG",8806]],
                PARAMETER["False northing",0,
                    LENGTHUNIT["metre",1],
                    ID["EPSG",8807]]],
            CS[Cartesian,2],
                AXIS["(E)",east,
                    ORDER[1],
                    LENGTHUNIT["metre",1]],
                AXIS["(N)",north,
                    ORDER[2],
                    LENGTHUNIT["metre",1]],
            ID["EPSG",26910]]],
    STEP[
        CONVERSION["Inverse of UTM zone 10N",
            METHOD["Inverse of Transverse Mercator",
                ID["INVERSE(EPSG)",9807]],
            PARAMETER["Latitude of natural origin",0,
                ANGLEUNIT["degree",0.0174532925199433],
                ID["EPSG",8801]],
            PARAMETER["Longitude of natural origin",-123,
                ANGLEUNIT["degree",0.0174532925199433],
                ID["EPSG",8802]],
            PARAMETER["Scale factor at natural origin",0.9996,
                SCALEUNIT["unity",1],
                ID["EPSG",8805]],
            PARAMETER["False easting",500000,
                LENGTHUNIT["metre",1],
                ID["EPSG",8806]],
            PARAMETER["False northing",0,
                LENGTHUNIT["metre",1],
                ID["EPSG",8807]],
            ID["INVERSE(EPSG)",16010]]],
    STEP[
        COORDINATEOPERATION["NAD27 to NAD83 (4)",
            SOURCECRS[
                GEOGCRS["NAD27",
                    DATUM["North American Datum 1927",
                        ELLIPSOID["Clarke 1866",6378206.4,294.978698213898,
                            LENGTHUNIT["metre",1]]],
                    PRIMEM["Greenwich",0,
                        ANGLEUNIT["degree",0.0174532925199433]],
                    CS[ellipsoidal,2],
                        AXIS["geodetic latitude (Lat)",north,
                            ORDER[1],
                            ANGLEUNIT["degree",0.0174532925199433]],
                        AXIS["geodetic longitude (Lon)",east,
                            ORDER[2],
                            ANGLEUNIT["degree",0.0174532925199433]],
                    ID["EPSG",4267]]],
            TARGETCRS[
                GEOGCRS["NAD83",
                    DATUM["North American Datum 1983",
                        ELLIPSOID["GRS 1980",6378137,298.257222101,
                            LENGTHUNIT["metre",1]]],
                    PRIMEM["Greenwich",0,
                        ANGLEUNIT["degree",0.0174532925199433]],
                    CS[ellipsoidal,2],
                        AXIS["geodetic latitude (Lat)",north,
                            ORDER[1],
                            ANGLEUNIT["degree",0.0174532925199433]],
                        AXIS["geodetic longitude (Lon)",east,
                            ORDER[2],
                            ANGLEUNIT["degree",0.0174532925199433]],
                    ID["EPSG",4269]]],
            METHOD["HORIZONTAL_SHIFT_GTIFF"],
            PARAMETERFILE["Latitude and longitude difference file","ca_nrc_ntv2_0.tif"],
            OPERATIONACCURACY[1.5],
            ID["DERIVED_FROM(EPSG)",1313]]],
    STEP[
        CONVERSION["UTM zone 10N",
            METHOD["Transverse Mercator",
                ID["EPSG",9807]],
            PARAMETER["Latitude of natural origin",0,
                ANGLEUNIT["degree",0.0174532925199433],
                ID["EPSG",8801]],
            PARAMETER["Longitude of natural origin",-123,
                ANGLEUNIT["degree",0.0174532925199433],
                ID["EPSG",8802]],
            PARAMETER["Scale factor at natural origin",0.9996,
                SCALEUNIT["unity",1],
                ID["EPSG",8805]],
            PARAMETER["False easting",500000,
                LENGTHUNIT["metre",1],
                ID["EPSG",8806]],
            PARAMETER["False northing",0,
                LENGTHUNIT["metre",1],
                ID["EPSG",8807]],
            ID["EPSG",16010]]],
    USAGE[
        SCOPE["unknown"],
        AREA["Canada - onshore - Alberta; British Columbia; Manitoba; New Brunswick; Newfoundland and Labrador; Northwest Territories; Nova Scotia; Nunavut; Ontario; Prince Edward Island; Quebec; Saskatchewan; Yukon; offshore east coast."],
        BBOX[40.04,-141.01,83.17,-47.74]]]

This example shows the PROJAttributeReprojector parameters configured to use an epoch with a PROJ pipeline.

Note that the desired deformation model is referenced in the pipeline string.

Epochs may also be provided via an attribute value or user parameter.

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.

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-Specific Reprojection Transformers (Recommended)

Features with attributes containing coordinates to be reprojected.

Features with reprojected attributes as specified in parameters.

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.

Table Tools

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

Note: Not all tools are available in all transformers.