FME Transformers: 2024.2

Categories
Spatial Analysis

Spatial Analysis

Related Transformers
2DBoxReplacer
2DGridAccumulator
2DGridCreator
BoundingBoxReplacer
BoundsExtractor
Creator
HullAccumulator
HullReplacer
MinimumSpanningCircleReplacer
RasterExtentsCoercer
Categories
Spatial Analysis

Spatial Analysis

Related Transformers
2DBoxReplacer
2DGridAccumulator
2DGridCreator
BoundingBoxReplacer
BoundsExtractor
Creator
HullAccumulator
HullReplacer
MinimumSpanningCircleReplacer
RasterExtentsCoercer

BoundingBoxAccumulator

Creates a rectangular polygon that spans the extents of all input features.

Jump to Configuration

Typical Uses

  • Determining the extents of an entire set of features

How does it work?

The BoundingBoxAccumulator receives features with any geometry type and creates the minimum enclosing rectangular polygon that contains all features. The rectangle is not rotated. Its sides are parallel to the x and y axes.

If features are 3D, including point clouds, the bounding box will contain their footprint - that is, their x and y extents.

If an output bounding box has zero area (the bounding box of a single point or vertical line, for example), it will become a point or line as appropriate.

The output bounding box can retain attributes from the input features, either as a single set of attribute values or a list of values from all input features.

Examples

In this example, we have a set of rapid transit lines and want to generate the bounding box that contains all features.

Note that they have an attribute containing the name of the line.

The features are routed into a BoundingBoxAccumulator.

In the parameters dialog, we enable Generate List to add a list attribute to the output bounding box. It is named Lines and will contain the LINE value from all input features.

One bounding box is produced, spanning all input features. Note the list attribute containing the LINE values.

Usage Notes

Creating and Modifying Boxes and Rectangles

Creating rectangular geometry is a common task. These transformers do so in a variety of ways.

Transformer

Use this to...

Transformer Description

Creator

Create one or more new features with box geometry of a specific size and position (when Geometry Object is Box).

Creates features using the parameters supplied, and sends them into the workspace for processing.

2DBoxReplacer

Replace an existing feature’s geometry with a box of a specific size and position.

Replaces feature geometry with a 2D box defined by specified minimum and maximum x and y values.

BoundingBoxAccumulator

Create one rectangle that encompasses all features received.

Creates a rectangular polygon that spans the extents of all input features.

BoundingBoxReplacer

Individually replace the geometry of each feature with a rectangle that covers its extents.

Replaces feature geometry with a box or cube that spans the extents of the feature.

RasterExtentsCoercer

Individually replace the geometry of each raster feature with a rectangle.

Replaces the geometry of input raster features with a polygon covering either the extents of a raster or the extent of data within a raster.

BoundsExtractor

Extract the coordinate values that describe an individual feature’s bounding box (or cube) and store them as attributes.

Extracts a feature’s minimum and maximum coordinate values into attributes.

2DGridAccumulator

Create a series of regularly-spaced rectangles that span the extent of all features (when Type of Grid to Create is Polygons).

Creates a regular grid of points or rectangular polygons that span the extents of all input features.

2DGridCreator

Create a series of regularly-spaced rectangles of a specific size and position (when Type of Grid to Create is Polygons).

Creates a regular grid of points or rectangular polygons of a specified size, position, and coordinate system.

Tiler and RasterTiler

Chop features into a series of rectangular tiles, specified in a similar fashion to the 2DGridAccumulator.

Splits input features into a series of tiles by specifying either tile size (in ground units) or total number of tiles.

Splits each input raster into a series of tiles by specifying either a tile size in cells/pixels or the number of tiles.

Configuration

Input Ports

Features with geometry.

Output Ports

A rectangle spanning the extent of all input features, optionally with attributes as specified in parameters.

Features without valid geometry are output via this port.

Rejected features will have an fme_rejection_code attribute with one of the following values:

INVALID_GEOMETRY_VERTICES

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.

Parameters

Group By

The input features may be partitioned into groups based on attribute values.

One bounding box is output for each group.

If Group By is not specified, all input features will be processed together and a single bounding box will be output.

Complete Groups

 

Select the point in processing at which groups are processed:

When All Features Received

This is the default behavior. Processing will only occur in this transformer once all input is present.

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 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 When All Features Received 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.

Accumulation Mode

Drop Incoming Attributes: The bounding box receives no attributes.

Merge Incoming Attributes: The bounding box receives all attributes from input features.

Use Attributes From One Feature: The bounding box receives all attributes from one representative feature.

Generate List

When enabled, adds a list attribute to the output bounding box with values from multiple input features.

List Name

Enter a name for the list attribute.

Add To List

All Attributes: All attributes will be added to the output features.

Selected Attributes: Enables the Selected Attributes parameter, where specific attributes may be chosen for inclusion.

Selected Attributes

When Add To List is Selected Attributes, specify the attributes to include.

Note  List attributes are not accessible from the output schema in FME Workbench unless they are first processed using a transformer that operates on them, such as ListExploder or ListConcatenator. Alternatively, AttributeExposer can be used.

Editing Transformer Parameters

Transformer parameters can be set by directly entering values, using expressions, or referencing other elements in the workspace such as attribute values or user parameters. Various editors and context menus are available to assist. To see what is available, click beside the applicable parameter.

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.

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.

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.

For more information, see Transformer Parameter Menu Options.

Reference

Processing Behavior

Group-Based

Feature Holding

Yes

Dependencies

None

Aliases

History

 

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