Problem with big spikes in roads

[m-gerhold]

Hi all,

I'm having some issues when generating roads with 3Dfier. For other classes (terrain, buildings etc.) the results look good, but when calculating roads 3Dfier will sometimes output big spikes. These spikes do not seem to happen with any other class. I have tried calculating the road polygons as "terrain" in 3Dfier instead and the spikes did not appear there, so that seems to prove the spikes have something to do with the way 3Dfier generates roads.

I assume this problem happens during the lifting process for roads. Also, in the stiching process terrain objects next to these roads are then sometimes stitched to these spikes to fill the height gaps, which also generates these spikes in the terrain (see example 2). The spikes also arent only above ground, in some cases a road will also get spikes above and below the ground (also example 2).

I have tried different lifting options (changing radius_vertex_elevation and also filter_outliers and flatten for roads), however this has not had the desired effect. Raising the radius has instead only created even more spikes at different locations. They also don't seem to be connected to outliers in the point cloud (for the roads I'm using height points from a DEM that I have converted to LAS) and again, the spikes don't appear when generating as "terrain".

Is there anything else I could try to prevent these spikes in roads? Or is this possibly a bug? Using the "terrain" class for roads prevents these spikes, but is not a good solution, because the roads then aren't as flat and have height points within them.

I would really appreciate some help with this. Thank you in advance!

Example 1:

Example 2:

Road has no spikes when calculated as "terrain":