Limiting Las2Tin triangle formation

[Dennis Shimer]

Is there a way to limit edge triangles based on any criteria? For example maximum leg length, minimum area, minimum angles between legs, or combinations of these factors.

Dennis Shimer

[Martin Isenburg]

Hello,

> Is there a way to limit edge triangles based on any criteria? For example
> maximum leg length, minimum area, minimum angles between legs, or
> combinations of these factors.

not currently. it would be reasonably easy to exclude all triangles
that have an edge length longer than, say 50 meters, from being
output. Similarly to las2iso and las2dem that have the '-kill 50'
parameter. but that could also kill triangles large across water
bodies in the interior of the triangulation. would that be a problem?

Regards,

martin @lastools

[Dennis Shimer]

Just one opinion but it would be a problem for me, though if it was a choice between needing to carefully tune the parameter or getting unlimited length triangles I would choose the former. In my situation the best solution would be something like

IF the triangle has a leg that doesn't border another triangle, AND IF the leg greater than the max length, THEN remove it.

The solutions I have seen in practice needs to take an iterative approach since once you remove a triangle there may be one next to it that is now "external", though just checking the faces which bordered it may also work.

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[Martin Isenburg]

Hello,

> IF the triangle has a leg that doesn't border another triangle, AND IF the
> leg greater than the max length, THEN remove it.

since I had this exact algorithm already "lying around" it was just a
matter of copy and paste to add it to las2tin.exe. Note that
las2tin.exe should also handle batch processing now. the following
command will create a TIN and then recursively remove all triangles
with a leg longer than 25 from the boundary.

las2tin -i lidar.laz -o tin.shp -concavity 25
las2tin -i *.las -concavity 25

get the updated version at
http://www.cs.unc.edu/~isenburg/lastools/download/las2tin.exe
http://www.cs.unc.edu/~isenburg/lastools/download/las2tin_README.txt
http://www.cs.unc.edu/~isenburg/lastools/download/lastools.zip

regards,

martin @lastools