lasboundary - 3D envelope

[Jorg]

Martin,

It would be a great tool (at least for what I am doing at the moment) to have lasboundary not just generating a 2D-shape file but a 3D one - and I do not just mean the bounding box - maybe it could be called lasenvelope or just add it to lasboundary. As far as I can see this is not possible with the current version. What I would then do with this 3D-shape file is to select points from a second pointcloud that fall into this 3D-envelope.

A variation of this would be to have a tool that selects points from a pointcloud on the basis that they are located within a certain 3D-distance of the points present in another pointcloud - following a somewhat similar strategy as lasnoise regarding the specification of the parameters.

What is this good for ? We are currently flying two Riegl scanners at the same time, a Q680i-S (1064nm) and a VQ820G (532nm). The aim is to combine the two and get a dimensionless parameter similar to ndvi. One step that would make life easier would be what I am saying above.

One more thing - for the 2D- and also for a 3D-lasboundary, it would also be great to have a function that extends (or reduces) the size of the resulting shape by some margin. Yes, one can use other software for this, but it would be a great addition to lasboundary too.
Cheers,
Jorg.

[Martin Isenburg]

Hello Jorg,

the first (of several) stumbling blocks for a "3D shape" would be that there is not yet a general "3D Shapefile" format that has wide-spread support in GIS packages to do such inside / outside operations. What may be easier to implement and more usable in other tools may be the creation of two height rasters - a lower one and an upper one - that enclose / envelope the points and then to use the two surfaces defined in combination with two runs of lasheight to cut away the points outside this envelope. Maybe this workflow works for you:

lasgrid -i one.laz -lowest -step 2 -o lower.bil

lasgrid -i one.laz -highest -step 2 -o upper.bil

lassort -i lower.bil -o lower.laz

lassort -i upper.bil -o upper.laz

lasindex -i lower.laz

lasindex -i upper.laz

lasheight -i two.laz -ground_points lower.laz -drop_below 0 -o two_above.laz

lasheight -i two.laz -ground_points upper.laz -drop_above 0 -o two_enclosed.laz

Instead of using 0 you may want to use 0.5 and -0.5 for a slightly "buffered" envelope.

Regards,

Martin @rapidlasso

 

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