Solves proximity conflicts between features using a variant of the Nickerson displacement algorithm. This transformer is usually used after generalization.
Input and Output Ports
The features routed into the transformer through the Base port are geometrically frozen (cannot move).
The features routed in through the Candidate port are compared against the Base feature(s), displaced as necessary, and exit through the Displaced port. If no displacement occurred, they exit through the Untouched port.
Each comparison/displacement is independent of the others.
Base features with geometries other than point, curve or area (polygon or ellipse or donut) will exit through the InvalidBase port. Candidate features with geometries other than point, curve or simple area (polygon or ellipse) will exit through the InvalidCandidate port.
The ExtraBase port holds extra Base features as described in the Base Type parameter below.
You can use this option to narrow down which candidate features to compare with which base features.
Process At End (Blocking): This is the default behavior. Processing will only occur in this transformer once all input is present.
Process When Group Changes (Advanced): This transformer will process input groups in order. Changes of the value of the Group By parameter on the input stream will trigger processing on the currently accumulating group. This may improve overall speed (particularly with multiple, equally-sized groups), but could cause undesired behavior if input groups are not truly ordered.
There are two typical reasons for using Process 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 Process At End (Blocking) 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.
Specifies how much the displacement at one point in the candidate feature's geometry should affect the neighboring points. A lower value means that the candidate geometry can be deformed easily, while a higher value means that it will try its best to keep its original shape.
The Minimum Separating Distance parameter specifies the minimum separating distance between the candidate feature's geometry and the base feature's geometry after displacement.
The Displace Endpoints parameter specifies whether or not to displace the endpoints of candidate features whose geometries are unclosed lines.
The Base Type parameter specifies whether only a single Base feature will be used, or whether all Base features will be used. If Bases First is selected, then the transformer assumes that all Base features will enter the transformer before any Candidate features. Any further Base features that arrive after the first Candidate will be output through the ExtraBase port. The same goes for any Base features after the first when in Single Base mode.
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.
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.
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.
Set values depending on one or more test conditions that either pass or fail.
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.
|These functions manipulate and format strings.|
|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
Transformers with table-style parameters have additional tools for populating and manipulating values.
Enabled once you have clicked on a row item. Choices include:
Cut, Copy, and Paste
Enabled once you have clicked on a row item. Choices include:
Cut, copy, and paste may be used within a transformer, or between transformers.
|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 populates the table with a set of new attributes read from a dataset. Specific application varies between transformers.|
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.
FME Licensing Level
FME Professional edition and above
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Keywords: displacement resolve conflict generalization Nickerson generalize NickersonDisplacer