ReprojectAngleCalculator

Converts a given angle from one coordinate system to another.

Typical Uses

Determining angles for text and symbol rotation
Reprojecting angles stored as attribute values

How does it work?

The ReprojectAngleCalculator receives features with geometry and reprojects a given angle from one coordinate system to another.

The transformer starts with two points. One is the first coordinate of the input feature’s geometry, and the second is calculated from that point using the Original Line Angle and Original Line Length. Both of these points are reprojected from the Source Coordinate System to the Destination Coordinate System. A new angle is calculated from the reprojected points and added to the output feature as an attribute value.

The Original Line Angle may be provided as an attribute value, constant value, expression, user parameter, or conditional value.

Original Line Length is also required to perform the calculation, in the Source Coordinate System’s ground units. The length may be provided as an attribute, expression, constant, parameter, or conditional value. A length of one (1) is often appropriate for calculating rotation around a point, such as text and symbol rotation angles.

Both the Source and Destination Coordinate Systems must be specified explicitly.

Reprojections are generally performed using the FME (CS-Map) library, however, this transformer will honor the Workspace Parameter Reprojection Engine, and will use the Esri Reprojection Engine if it is selected there, with or without an Esri product being installed.

Z values are not supported.

This transformer assumes all coordinate systems are Cartesian.

Examples

Example: Calculating reprojected rotation angles in a CAD file

In this example, we have a CAD file containing traffic signal locations and labels. The original file is projected as UTM83-10, but we want to know what will happen to the label rotation if we reproject to BCPOLY-83.

Note that the label's autocad_rotation value is zero (0).

The features are routed into a ReprojectAngleCalculator.

Note that three format-specific attributes have been exposed - autocad_text_size, autocad_text_string, and autocad_rotation. This was done in the Autodesk AutoCAD DWG/DXF Reader parameters, Format Attributes, so that we can access their values.

In the parameters dialog, we set Original Line Angle to the exposed autocad_rotation attribute, and the Original Line Length to 1 (meter, in ground units).

Both the Source and Destination Coordinate Systems are specified explicitly.

The Reprojected Angle attribute is named _angle (the default name).

The output feature has a new attribute - _angle - with the value of the reprojected angle.

Note that the Coordinate System has not changed and is still UTM83-10. The feature itself has not been reprojected, its geometry not altered. The reprojection to BCPOLY-83 has only been used to calculate the _angle value.

Usage Notes

This transformer requires that features have geometry to provide an initial coordinate. Non-spatial features will not produce valid output. To create geometry for non-spatial data with coordinates as attributes, consider using a VertexCreator.

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

General

Original Line Length	Specify a distance, in the Source Coordinate System’s ground units.
Original Line Angle	Specify an angle, in the Source Coordinate System. Angle is measured counterclockwise from horizontal in degrees.
Source Coordinate System	Specify the coordinate system of the input features.
Destination Coordinate System	Specify the coordinate system the Original Line Angle is to be reprojected to. Note that the feature itself will not be reprojected, and this parameter is only used for calculation of the Reprojected Angle Attribute.

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.

How to Set Parameter Values

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

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

Table Tools

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.

Reference

Processing Behavior	Feature-Based
Feature Holding	No
Dependencies	None
Aliases
History

FME Community

The FME Community is the place for demos, how-tos, articles, FAQs, and more. Get answers to your questions, learn from other users, and suggest, vote, and comment on new features.

Search for all results about the ReprojectAngleCalculator on the FME Community.

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