Detects features that are matches of each other. Features are declared to match when they have matching geometry, matching attribute values, or both. A list of attributes which must differ between the features may also be specified.

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Typical Uses

  • Change detection
  • Feature merging (data joins) based on geometry

How does it work?

The Matcher can receive any number of input feature streams. All features are compared against all other features, and matches are identified based on the parameters defined.

Options for matching include geometry and/or attributes, and you may also define attributes that must differ.

All features that find a match are output via the Matched port (that is, if two features match each other, both of them are output here). Each set of matches is given a new numeric Match ID attribute that can be used to identify them as a matching group.

A single copy of each set of matched features is sent to the SingleMatched port. The attributes on these features are merged on to one output feature. Using this port, the Matcher is capable of doing multi-feature merging using geometry as the key. This complements the FeatureMerger, which only accepts attributes, and not geometries, as keys.

Features that do not find a match are output via the NotMatched port.

Usage Notes

  • The ChangeDetector provides an alternative (but less general) approach which may be more convenient for certain applications.
  • When looking for matches based only on attributes, consider the FeatureJoiner or FeatureMerger for better performance.

Choosing a Feature Joining Method

Many transformers can perform data joining based on matching attributes, expressions and/or geometry. When choosing one for a specific joining task, considerations include the complexity of the join, data format, indexing, conflict handling, and desired results. Some transformers use SQL syntax, and some access external databases directly. They may or may not support list attribute reading and creation.

Generally, choosing the one that is most specific to the task you need to accomplish will provide the optimal performance results. If there is more than one way to do it (which is frequently the case), time spent on performance testing alternate methods may be worthwhile. Performance may vary greatly depending on the existence of key indexes when reading external tables (as opposed to features already in the workspace).


Input Ports

Output Ports


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.


Processing Behavior


Feature Holding


Dependencies None
FME Licensing Level FME Base Edition and above



Data Quality

FME Community

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Examples may contain information licensed under the Open Government Licence – Vancouver