MeasureExtractorToZ
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Overview
The FME geometry model supports extracting measures from features; however the only transformer to do this creates an FME list of measures. In some cases a user may wish to transfer the measures to Z values, and this is what the MeasureExtractorToZ workspace does.
Input
This transformer accepts as input any feature with measures attached.
Above: Input features should have a measure. .
Output
The output from this transformer is the same set of features, but with a Z values set to the individual measure for that vertex.
Above: Output features have their measures as Z values.
Methodology
Difficulties arise because there is no way in FME to set the Z value for a single vertex on a line; only for the full line itself.
Therefore two different methods were tried to achieve the measure to Z transfer.
- A DEM method. The features are chopped into points, the measure applied as a Z, and the points treated as a DEM so the original features can be draped back over them.
- A TCL method. The measures are extracted and applied to each vertex using a TCL script.
Detailed Description: DEM
This workspace is surprisingly simple - but the method is really not very good.
Above: The workspace definition..
In the workspace, lines are cut up into points using the Chopper. That means when we extract the measure with the MeasureExtractor there is no problem assigning it to the correct vertex with the 3DForcer.
Z values are transferred back onto the original features by draping them onto the points with the SurfaceDraper.
The key to the workspace is getting the SurfaceDraper settings correct, so that the Z value is taken directly from a point and not interpolated.
Above: The SurfaceDraper settings.
Detailed Description: TCL
This workspace looks even simpler, but has the hidden complexity of a TCL script buried inside a TCLCaller. I'd think this would work better (much faster) especially with large-scale datasets.
Above: The TCL workspace definition.
Above: The TCL script.
