LineOnLineOverlayer
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LineOnLineOverlayer is a Workbench Transformer.
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Description
Performs a line-on-line overlay.
All input lines are intersected against each other and resultant lines features are created and output. The intersection points are created into point features and holds the merge list of attributes of the original intersected lines.
Attributes
When attributes are merged between features, existing attributes are not replaced. Therefore if the pair of lines being overlayed have attributes with the same name, then the values will not be transferred from one to the other. This can be worked around by renaming (AttributeRenamer), prefixing (AttributePrefixer), or removing (AttributeRemover or AttributeKeeper) attributes to avoid name collisions
Geometry Intersections
Some users will want to know which lines overlay each other, but without chopping the geometry at the intersection points. The SpatialFilter transformer is an alternate method of this but, if sticking with the LineOnLineOverlayer, you can simply route the source data around the transformer as a second stream, and attach the information using a FeatureMerger transformer where the bypassed data is the requestor and the output point data is the supplier.
Above: Here a user is using this method to put intersection information back onto the original geometry.
List
If the optional list name is supplied, a list of all the attributes of each line that intersected the resultant feature is created and appended to the point features only.
Collinear Segments
The Separate Collinear Segments option allows you to select whether both (or more) overlapping segments are output (Yes), or whether only one segment is output for each overlap (No). When choosing to output only one segment for each overlap then it may be difficult to predict which of the "original" geometries & attributes are preserved. In general, the features that arrive at the LineonLineOverlayer FIRST, will be the ones that form the separate segments. Use the FeatureHolder or Sorter transformers to change the sequence of features if this is important.
If the optional list name is supplied, AND the separate collinear segments setting is NO, then a list of all the attributes of each line that was merged is created and appended to the line features only. If the separate collinear segments is YES, then no list is ever created on the line features (because no merging would take place).
Measures
Measures: LineOnLineOverlayer will preserve measures - based on the rules described above.
Example
The attached workspace shows an example use of the LineOnLineOverlayer transformer.
Workspace Screenshot
Above: LineOnLineOverlayer Example Workspace.
The workspace generates a number of line features and sends them into the LineOnLineOverlayer.
Because some of the line segments are collinear (ie they overlap precisely) then the transformer setting 'Separate Collinear Elements' has an effect on the output. You should try turning this setting on and off to see the difference in output. Particularly note how the list name interacts with this setting - the list on the line features is a list of merged elements, therefore turning off the merging will result in no list on the output lines.
Output
Above: LineOnLineOverlayer Example Output.
Notice in the output that an intersection point is created at each junction of the line features. If a list is specified then the point features identify which lines intersected at that point.
