Question

Producing a clipped LAS file on the basis of features from a DGN file

P

Fellow FME programmers. I have a large LAS and a DGN file that goes with it, is there a way to generate a clipped LAS file on the basis of a subset of features in the DGN ? I know I can overlay and view it, but I need to clip and produce a subset LAS file.

6 replies

jdh
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Badge +22

Is there a reason that the Clipper won't do the job?

itay
Rank
Badge +16

Hi @prasadkmurthy,

Looks like some of the features going into the LAS writer are not pointclouds :

"LAS writer: Failed to obtain point cloud from feature. Only features with point cloud geometry are expected" I suggest you add a Geometry Filter before the LAS writer to filter out these features.

Hope this helps.

P

Thanks @itay I also wanted to check what is the best way to convert selected featuretypes in the DGN file into "clipper" objects that can be fed to the Clipper transformer ? Any pointers appreciated.

I will add the Geometry filter as suggested by you.

itay
Rank
Badge +16

Thanks @itay I also wanted to check what is the best way to convert selected featuretypes in the DGN file into "clipper" objects that can be fed to the Clipper transformer ? Any pointers appreciated.

I will add the Geometry filter as suggested by you.

What do you mean by convert selected features? 1 thing I would test for is the following: are the features area features? again using the GeometryFilter.

 

 

redgeographics
Rank
Userlevel 5
Badge +25

Thanks @itay I also wanted to check what is the best way to convert selected featuretypes in the DGN file into "clipper" objects that can be fed to the Clipper transformer ? Any pointers appreciated.

I will add the Geometry filter as suggested by you.

In addition to what @itay says, if your DGN features are lines you can use an AreaBuilder to attempt to build areas from them. The Clipper features have to be areas.

 

 

Inspect your data beforehand to get an idea of what it contains.

 

jdh
Rank
Badge +22

Yes, it looks like the clipper rejected 152 features. Use a GeometryFilter to make sure the dgn is areal. If they are self closing polylines you can use a GeometryCoercer to convert to areal, if it takes multiple features to create the outline, then you'll want to use an AreaBuilder, and you may need to set a Snapping Tolerance. Be advised that an AreaBuilder requires a topologically correct input (all lines are broken at intersections) and will create areal features for all potential polygons. ie a donut will have both the donut and the hole as separate features.

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