[GRASS-user] Lidar points height from ground

[Daniel Victoria]

Hi all,

I'm trying to calculate the height from the ground of several lidar
points (15million) in order to get the number of points that occur at
different height levels. I read some older posts about using r.in.xyz
(or r.in.lidar in grass 7) but I could not understand how to count the
number or points that have height from 0 to 5 m above the ground, for
instance. So, I'm trying to do the following.

1) import points using v.in.lidar (Grass 7 ubuntu linux)
2) create a column in the database for the ground height and one for elevation
3) populate height column from ground raster (generate in another
process) using v.what.rast
4) calculate elevation as zcoord - ground for each point (v.db.update)

As you might imagine, this takes a long time. Just to import a 400Mb
lidar file takes around 50min.
Is there any easier way that I'm not envisioning?

I'm running Grass 7 with liblas on a Ubuntu Virtual Machine and sqlite backend.

Thanks
Daniel