Bufferer

In this example, we buffer arterial streets (shown in blue) to find address points that fall within a fixed distance of them. The streets data is in a UTM coordinate system, with ground units in meters.

The arteries are routed into a Bufferer.

We enter a Buffer Distance of 50, and leave the Buffer Distance Units as the default setting Ground Units (None). This will produce buffers of 50 meters to either side of the street.

The Buffer Type is the default, Area (2D) .

The buffered streets are then sent to a SpatialFilter, along with the address points, and are tested for points that fall within the buffers.

In this example, we create buffer zones around rapid transit lines. The source data is KML, in a geographic lat/long projection.

As the ground units are in degrees, the data must be reprojected before making calculations in units like meters or feet. The Buffer Distance Units parameter will take care of that.

The lines are routed into a Bufferer.

In the parameters dialog, we select Meters as our ground unit of choice, and set a Buffer Distance of 150.

The resulting Output buffer polygons retain the attributes of the original features, and are projected in the original lat/long coordinate system.

In this example, we take a point dataset of food carts that has an attribute containing the average number of daily customers they serve. We route the points into the Bufferer.

A bit of experimentation shows that dividing the daily traffic numbers by 10 will produce a desirable range of bubble sizes, and so we set the Buffer Distance to the value of the DAILY_TRAF attribute, divided by 10.

The resulting buffers are colored according to the category of food cart (type of food served).

If the Buffer Type parameter is Area (2D), then only 2D geometries are accepted as input.

If the Buffer Type parameter is Solid, then all geometry types are accepted as input.

An area or solid representing the region that is within the specified buffer distance of the input geometry. A null geometry is output if this region would be empty.

The original geometry is not output.

Features with invalid geometries are output through this port along with an additional attribute, fme_rejection_code, to indicate the reason for rejection.

If the Buffer Type parameter is Solid, negative buffer distance will cause a feature to be rejected.

If the Buffer Type parameter is Area (2D) non-2D geometries will be rejected.

If the Buffer Distance Units parameter is set to anything other than Ground Units (None), features without coordinate systems will be rejected.

Rejected Feature Handling: can be set to either terminate the translation or continue running when it encounters a rejected feature. This setting is available both as a default FME option and as a workspace parameter.

These parameters are only enabled when the Buffer Type is Area (2D).

End Cap Style	When buffering a point or curve, you can select an end-cap style. Choices include: Arc Circular arcs (default) Round Interpolated lines - smoothness is controlled by the Interpolation Angle parameter. Square Squared None No end caps
Corner Style	When buffering a curve or area, you can select a corner style. Choices include: Arc Circular arcs (default) Round Interpolated lines Smoothness is controlled by the Interpolation Angle parameter. Miter Pointed The Miter Limit parameter must be specified to use Miter. Bevel Blunt
Miter Limit	Miter Limit This parameter controls how pointed a buffered corner can be before it is beveled. It is the highest value that the ratio of corner distance to offset is allowed to have before truncation occurs. A higher number allows for more extreme corner angles. Black line: Original line Red line: Offset curve A: Corner distance B: Offset Miter Ratio = Corner distance / Offset
Interpolation Angle	Used for the Round End Cap Style and the Round Corner Style. It controls the smoothness of the interpolated lines in the output buffer boundaries, specifying what angles should be used to approximate the circular corner. As this parameter decreases in value, the smoothness of the interpolated corners increases. The value is specified in degrees and must be greater than 0 and less than or equal to 90.
Buffer Mode	Controls whether input geometries are simplified before buffering. Standard (Fast): Input geometries are generalized by as much as 1% of the Buffer Distance before processing. This can result in dramatic performance improvements. When using an inexact Corner Style (Round, Bevel, or Miter), the output may differ by more than 1%. Precise: Input geometries are buffered as is. This can result in long runtimes for inputs which contain detail that is small relative to the Buffer Distance.
Dissolve On Attributes	Allows dissolving groups of buffered features with common values for the specified attributes. By default, no dissolving of buffered features takes place.
Dissolve On Attributes Mode	Process At End (Blocking): This is the default behavior. Processing will only occur in this transformer once all input is present. Process When Dissolve Attributes Change (Advanced): This transformer will process input groups in order. Changes of the value of the Dissolve On Attributes 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. Considerations for Using Dissolve On Attributes There are two typical reasons for using Process When Dissolve Attributes Change (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 Dissolve On Attributes 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 Dissolve On Attributes value need to arrive before any features (of any feature type or dataset) belonging to the next group. In this case, using Dissolve On Attributes 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.

When enabled, adds a list attribute to the Buffered output features. This parameter is useful when using Dissolve On Attributes or if input features contain aggregates. Within each group or aggregate, within each dissolved region, attributes from an input feature with the largest area are stored at the head of the list, and no order is defined for the remaining elements.

This parameter is only enabled when the Buffer Type is Solid.

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.

Note: Not all tools are available in all transformers.