SpatialRelator

Example: Finding spatial relationships between lines and areas

In this example, we compare a set of line features (bike paths) with polygons representing city parks. The bike paths are the Requestor - the features we want information about - and the parks are the Supplier that they will be compared to. Only bike paths with added attributes will be output - the parks will be discarded after they have been used to perform the spatial analysis.

In the SpatialRelator parameters dialog, we make the following selections:

Spatial Predicates to Test: for this case, we will select the spatial relationships we are interested in:
Generate List: generating a list is the default choice, and supports adding attributes for multiple matches. Under Add to List, we choose Selected Attributes, and then select DogPark and ParkName:

Looking at the results in the Data Inspector, with the Parks layer shown for reference, we can see that all of the path segments now have a _related_candidates attribute showing how many park features they matched. Feature 10, highlighted in blue, crosses from one park into another, and so shows two entries for INTERSECTS in its _relationships list attribute.

The geometry of the features has not been altered.

Spatial Transformers Comparison Matrix

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 (optionally including self-intersections), splitting features, and creating new geometry.
Clipper	Yes	Yes	No	No	Point Text Curve Area 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: Curve includes Lines, Arcs, and Paths. Area includes Polygons, Donuts, and Ellipses.

The Effect of Spatial Transformer Choice on Performance

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. As an example, when comparing address points to building polygons, there are a few ways to approach it.

The first example, using a SpatialFilter to test whether or not points fall inside polygons, produces the correct result. But the SpatialFilter is a fairly complex transformer, able to test for multiple conditions and accept a wide range of geometry types. It isn’t optimized for the specific spatial relationship we are analyzing here.

With a SpatialFilter:

The second example uses a PointOnAreaOverlayer, followed by a Tester. The features output are the same as in the first method, but the transformer is optimized for this specific task. The difference in processing time is substantial - from 54.3 seconds in the first configuration, down to 13.7 seconds in the second one.

With a PointOnAreaOverlayer and a Tester:

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

Requestor

Point, line, area, and text features that will be compared and then output with a tagged list describing the relationships.

Supplier

Point, line, area, and text features that will be used to compare with Requestor features, but not output.

Output

These are the Requestor features with the new attributes added. One list entry is made for each of the Suppliers that has at least one matching predicate.

Requestor and Supplier features with invalid geometries will be rejected and output via this port. If predicates are provided via an attribute, Supplier features with no or invalid predicates will also be output via this port.

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

INVALID_BASE_GEOMETRY_NOT_OGC_VALID
INVALID_BASE_GEOMETRY_TYPE
INVALID_BASE_GEOMETRY_VERTICES
INVALID_CANDIDATE_GEOMETRY_NOT_OGC_VALID
INVALID_CANDIDATE_GEOMETRY_TYPE
INVALID_CANDIDATE_GEOMETRY_VERTICES
INVALID_CANDIDATE_PARAMETER_PREDICATE
INVALID_GEOMETRY_TYPE
MISSING_CANDIDATE_PARAMETER_PREDICATE

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.

Transformer

Group By

This parameter is used to indicate that only Requestors and Suppliers that have the same value for certain attributes should be compared. Both the Requestors and Suppliers must having matching attribute names and values.

Group By Mode

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.

Tests

Support Mode	Support Aggregates: (default) Both multi and aggregate geometries will be supported. However, the only available predicates will be Contains, Equals, Intersects, Touches, and Within. The Overlaps predicate and the Crosses predicate will not be supported. 9-character masks representing Dimensionally Extended 9 Intersection Matrices will also not be supported. Support All Predicates: All the predicates described in the Spatial Relations Defined page will be supported, except Disjoint. However, aggregate and multi geometries will not be supported.
Spatial Predicates to Test	This parameter lists the spatial predicates that will be used for comparisons between the Requestor and Supplier features. These can either be selected directly from the list, or taken from attribute values. Tests include: Requestor Intersects Supplier Requestor Equals Supplier Requestor Touches Supplier Requestor Contains Supplier Requestor is Within Supplier Requestor Crosses Supplier Requestor Overlaps Supplier Not all tests are available for aggregate or multi geometry. If the Support Mode is Support All Predicates, you may also test relationships using arbitrary 9-character masks. Such masks consist of the rows of a Dimensionally Extended 9 Intersection Matrix. Note that in order to use these masks with the SpatialRelator, you must assign them to an attribute on the Supplier features, and include the value of that attribute in the Tests to Perform clause (you cannot specify them directly). Multiple predicates may be specified in one attribute by separating them with a space. Note that this transformer does not allow a matrix representing a disjoint relationship to be used. This includes any matrix that has F or * in all of the four top-left elements. If you wish to find features that are disjoint to another feature, the SpatialFilter may be used. For more information about predicates, see Spatial Relations Defined.
Attributes that Must Differ	This attribute controls which attributes must have different values before a match is declared.
Curve Boundary Rule	This parameter specifies how to determine the boundary of curve and multicurve geometries. The Default Rule is that any curve endpoints that occur an odd number of times in the geometry as a whole, will be considered its boundary – that is, a linear loop (a line whose start point equals its endpoint) will not have any boundary. The other rule specifies that the curve or multicurve's boundary is the set of all its endpoints.

Output

Related Suppliers Count Attribute

This attribute specifies the name of an attribute that will be added to each Requestor, which stores the number of Suppliers with which the Requestor had at least one true relationship.

Calculate Cardinality of Intersections

If Yes, then for each Supplier that matches a Requestor, three attributes will be added to the corresponding list entry: card_point, card_line, and card_area. These count the number of points, lines, and areas that comprise the intersection of the Requestor and Supplier. For instance, a point is counted if two polygons touch at a vertex, a line is counted if they touch at an edge, and an area is counted if they overlap.

Attribute Accumulation

Merge Attributes

When checked, enables options for merging feature type attributes.

Accumulation Mode

Merge Supplier: Attributes from all features are merged. Conflicts are handled according to parameter Conflict Resolution.

Prefix Supplier: All Supplier attributes are prefixed with a value specified by the Prefix parameter.

Only Use Supplier: Only attributes from Supplier features are used.

Conflict Resolution

Specifies how to handle attribute conflicts when Accumulation Mode is Merge Supplier.

Use Requestor: Gives priority to Requestors.

Use Supplier: Gives priority to Suppliers.

Prefix

When Accumulation Mode is Prefix Supplier, the specified value prefixes Supplier attributes.

When attributes are merged down from Supplier to Requestor features, existing attributes are not replaced. Therefore if the Suppliers and Requestors have attributes with the same name, the values will not be transferred down.

This can be worked around by renaming, removing, or prefixing attributes to avoid name collisions. (See AttributeManager and BulkAttributeRenamer.)

Generate List

When checked, enables options for list generation. The default is On.

The list attributes will contain relationship and spatial join attribute values. Spatial relationship information is added in this form:

<LIST_NAME>{i}.de9im = [DE9IM string]
<LIST_NAME>{i}.pass{0} = [true PREDICATE 1]
<LIST_NAME>{i}.pass{1} = [true PREDICATE 2]
...
<LIST_NAME>{i}.pass{n} = [true PREDICATE n+1]

List Name

This parameter specifies the name of the list attribute that will be added to the Requestor features.

Note: List attributes are not accessible from the output schema in 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 Supplier attributes will be added to the Requestors.

Selected Attributes: Enables the Selected Attributes parameter, where specific attributes may be chosen to be added from the Suppliers to the Requestors.

Selected Attributes

Enabled when Add To List is set to Selected Attributes.

Specify the attributes you wish to be added from the Suppliers to the Requestors.

How to Set Parameter Values

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.

Related Transformers

PointOnPointOverlayer

SpatialFilter

TopologyBuilder

Processing Behavior	Group-Based
Feature Holding	Yes
Dependencies
FME Licensing Level	FME Professional Edition and above
Aliases
History
Categories	Data Quality Filters and Joins Spatial Analysis

SpatialRelator

Typical Uses

How does it work?

Usage Notes

Choosing a Spatial Transformer

Configuration

Input Ports

Output Ports

Parameters

Editing Transformer Parameters

Defining Values

Reference

FME Community