Intersector

Categories

Geometries

Spatial Analysis

Related Transformers

AreaOnAreaOverlayer

Bufferer

Clipper

LineOnAreaOverlayer

LineOnLineOverlayer

NeighborFinder

PointOnAreaOverlayer

PointOnLineOverlayer

PointOnPointOverlayer

SpatialFilter

SpatialRelator

TopologyBuilder

Computes intersections between all input features, breaking lines and polygons wherever an intersection occurs and creating nodes at those locations. Overlapping segments are reduced to one segment before being output.

Jump to Configuration

Typical Uses

  • Identifying intersections within a dataset
  • Reducing geometry to line segments
  • Intersecting linear features at junctions to create clean topology
  • Cutting overshoots at their intersection
  • Creating points (nodes) at intersections to find likely features

How does it work?

The Intersector takes all input features and compares them to each other. Features are split wherever there is an intersection. Split features receive attributes from intersecting features (a spatial join), and the number of overlaps encountered and segments created is counted.

Intersected segments are output, as well as nodes (point features) placed at the location of each intersection. Optionally, a list attribute can be created which will retain attributes for multiple matches.

Aggregates can either be deaggregated before processing or rejected.

Examples

In this example, we start with a set of park polygons and bike path lines, and want to split the polygons where the lines intersect them. To do that, we will first use the Intersector, then build the segmented areas.

The first step is to route both datasets into one Intersector.

The default settings will produce the results we want.

The Intersector reduces all of the geometry to line segments, and creates nodes at the intersection points.

By routing only the Intersected features through an AreaBuilder and then filtering for Parks only, we end up with park polygons, split where the bike paths ran through them.

In this example, we start with a dataset of street centerlines. The street geometry is as contiguous as possible - the line segments are not broken at intersections, as shown here with a selected street highlighted in yellow. We want to create intersections, and find out which streets cross at those intersections, using a list attribute.

The street dataset set is routed into an Intersector.

In the Intersector parameters dialog, Generate List is enabled. The list is named Intersections, and one selected attribute - NAME - will be captured in the new list.

At each intersection of the lines, they are split, and a node is placed at the intersection. The nodes have a list called Intersections, which contains the NAME attribute we requested, as well as the angle and direction of line it is referring to.

The selected node shown here has four items in the list, as four line segments converge at that point - Broughton St incoming and outgoing, and Alberni St incoming and outgoing.

The lists can be further manipulated - see About List Attributes.

Usage Notes

Choosing a Spatial Transformer

Many transformers can assess spatial relationships and perform spatial joins - analyzing topology, merging attributes, and sometimes modifying geometry. 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.

To correctly analyze spatial relationships, all features should be in the same coordinate system. The Reprojector may be useful for reprojecting features within the workspace.

Transformer

Can Merge Attributes

Alters Geometry

Counts Related Features

Creates List

Supported Types*

Recommended For
SpatialFilter Yes No No No
  • Point
  • Text
  • Curve
  • Area
  • Testing for the existence of spatial relationships between two sets of features, and routing them according to whether they pass or fail the test(s).
SpatialRelator Yes No Yes Yes
  • Point
  • Text
  • Curve
  • Area
  • Identifying the nature of spatial relationships between two sets of features.
AreaOnAreaOverlayer Yes Yes Yes Yes
  • Area
  • Finding polygon overlaps and extracting them into new geometry.
LineOnAreaOverlayer Yes Yes Yes Yes
  • Curve and Area
  • Finding intersections between lines and polygons, and splitting the lines where they intersect with the polygons.
LineOnLineOverlayer Yes Yes Yes Yes
  • Curve
  • Finding intersections between line features, splitting them, and generating new line geometry as well as points representing the intersections.
PointOnAreaOverlayer Yes No Yes Yes
  • Point and Area
  • Text and Area
  • Identifying points that fall within polygons, and merging attributes between them
PointOnLineOverlayer Yes Yes Yes Yes
  • Point and Curve
  • Text and Curve
  • Identifying where points fall on lines, and splitting the lines into new geometry.
PointOnPointOverlayer Yes No Yes Yes
  • Point
  • Text
  • Identifying points in the same location (within a tolerance), and merging attributes between them.
Intersector Yes Yes Yes Yes
  • Point
  • Text
  • Curve
  • Area
  • Finding intersections between all input features, regardless of geometry (including self-intersections), splitting features, and creating new geometry.
Clipper Yes Yes No No
  • Point
  • Text
  • Curve
  • Area
  • Surface
  • Solids
  • Raster
  • Point Cloud
  • Comparing features against a set of Clipper features, and splitting the features at or along the Clipper boundaries. Outputs both new and untouched geometry, identified as either Inside or Outside the Clipper.
NeighborFinder Yes In some cases No Yes
  • Point
  • Text
  • Curve
  • Area
  • Identifying the nearest other feature(s) to each feature being considered, either in another set of features or within the same feature set.
TopologyBuilder Yes Yes No Yes
  • Point
  • Text
  • Curve
  • Area
  • Analyzing spatial relationships between features to compute topology, splitting features and creating new geometry representing topologically significant nodes, edges, and faces, with associated attributes.

* Note that Curve includes Lines, Arcs, and Paths. Area includes Polygons, Donuts, and Ellipses.

Spatial analysis can be processing-intensive, particularly when a large number of features are involved. If you would like to tune the performance of your workspace, this is a good place to start.

When there are multiple ways to configure a workspace to reach the same goal, it is often best to choose the transformer most specifically suited to your task.

If performance is an issue in your workspace, look for alternative methods, guided by geometry.

Configuration

Input Ports

Features to be compared for intersections. Point, line, and area features are supported.

Output Ports

The intersected features are output to this port. If the List Name parameter was specified, these features will have an attribute containing their number of overlapping input features. They will also have all attributes of the original features.

The locations of topologically significant nodes are represented by point features and are output to this port. The transformer parameters modify which attributes are included on the output features.

Features which were smaller than the tolerance value collapse to a point and are output to this port.

All null, surface, solid, raster, and point cloud features are output through this port.

Features whose projection onto the xy-plane are not finite (i.e. nan or infinity coordinates) are also output from this port.

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 default behavior is to use the entire set of features as the group. This option allows you to select attributes that define which groups to form.

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.

Tolerance

The minimum distance between geometries in 2D before they are considered equal, in ground units.

If the tolerance is Automatic, a tolerance will be automatically computed based on the location of the input geometries. Additionally, a custom tolerance may be used.

Duplicate Nodes at Each Elevation

The creation of nodes can be calculated in 3D, if requested. Constructing nodes in 3D would mean that line segments would only share a node if they shared the same Z value at the point they intersected. Constructing nodes in 2D would mean that all intersecting segments would share a common node, regardless of their respective Z values.

For example, a situation where two lines (that crossed) represented roads, where one road was an overpass above the other road. with differing elevations.

If you constructed nodes in 3D, these two roads would not be linked to the same node where they crossed. Two nodes would be produced at the crossing point – each one with a different Z value.

If you constructed nodes in 2D, these lines would both link to a common node, which would be present at the location where they crossed.

In either the 2D or 3D case, the full dimensionality of the input is preserved in the output – 3D features are never converted to 2D.

The 2D or 3D choice only indicates how the nodes are created and which lines are linked to them; it does not affect the dimension of the features that are output.

Yes - Whenever 3D lines intersect at differing heights, two 2D nodes will be output via the Node port. Each node will have the same x and y coordinates, but a different node number.

No - Whenever 3D lines intersect at differing heights, a single 2D node is output at the intersection point.

Separate Collinear Segments

If Yes - causes overlapping segments not to be merged into a single segment: one copy is output for each original feature sharing the segment. Each such segment will have the respective original feature’s attributes as its main attributes, and attributes from all other collinear features will be added as a list attribute, if the list name was supplied.

When a coverage of polygons is input, the set of topologically significant lines which form their boundaries is output.

Aggregate Handling

Deaggregate: All input aggregates will be deaggregated, and each split part will be processed independently. With this setting, the transformer might output more features than were given as inputs.

Reject: All input aggregates will be rejected.

Treat Measures as

When new coordinates are added due to intersection, the measures at those coordinates are determined from existing coordinates.

Continuous: New measures will be computed from a linear interpolation of the neighboring coordinates along that segment.

Discrete: Measures will be set to the measures of the nearest coordinates along the intersected segment.

Direction

 

Name this optional attribute to include in generated lists.

On segment features, it indicates whether the attributes at that entry in the list come from a collinear feature that had the "same" or "opposite" direction as the output feature.

On node features, it indicates whether the attributes at that entry in the list come from a segment feature that is "outgoing" from the node or "incoming" to the node.

Overlap Count

Name the attribute to contain the number of collinear input lines that overlapped the output segment.

Segment Count

Name the attribute to contain the number of segments into which the segment’s original feature was divided.

If an input feature was broken into n output segments, each of those segments will have an attribute named <attribute name> which has a value of n.

Node Number

Name the attribute to contain a unique ID for each topologically significant node.

Accumulation Mode

Specifies how attributes should be accumulated.

Drop Attributes: All incoming attributes are removed from the features.

Merge Attributes: Merges all attributes from overlapping segments.

Use Attributes From One Feature: Takes all attributes from one representative feature.

Prefix

When Separate Collinear Segments is Yes, and Accumulation Mode is Merge Attributes, this value prefixes all incoming attributes on collinear segments. It does not affect node (point) output.

 

Generate List

When enabled, adds a list attribute to the output features, and the attributes of intersecting features are added to the list. Nodes will receive list attributes from all intersecting features, including direction and angle.

List Name

Enter a name for the list attribute.

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.

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

Enabled when Add To List is set to Selected Attributes. Specify the attributes you wish to be included.

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.

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.

Dialog Options - Tables

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.

Reference

Processing Behavior

Group-Based

Feature Holding

Yes
Dependencies  
Aliases  
History  

FME Community

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