[GRASS-dev] Re: lidar tools update in grass7

Markus Metz markus.metz.giswork at googlemail.com
Mon May 10 04:58:16 EDT 2010

Hi Sara,

your help is highly appreciated! There are no new commands, only one
in grass7 called r.resamp.bspline. Contrary to v.surf.bspline, it uses
a raster map as input and resamples that map to the resolution and
extends of the current computational region. The existing commands
have been modified and fixed where necessary. They should all run
faster now and some problems with the zones overlapping adjacent
subregions where eliminated. Still, more testing is always good, it
seems that the previous version of the lidar tools did not receive a
lot of testing or bug fixing...

There is one open issue with edge detection. v.lidar.edgedetection
uses two criteria, a high gradient threshold and a low gradient
threshold (hard and soft criterion). All points with a gradient larger
than high gradient threshold are classified as edges. All points with
a gradient larger than low gradient threshold and smaller than high
gradient threshold are investigated more closely, but only if they are
in the core interpolation zone and do not fall into an overlapping
zone. In my tests, it seemed to be ok to treat points in the
overlapping zone identical to points in the core zone. I understand
why the module is conservative and currently treats these points as
unknown and does not classify them as terrain or edge, but it seems to
me that this is a bit overly conservative. It would be great if you
could look into this issue! I could send you a patch for
v.lidar.edgedetection that classifies all points to either terrain or
edge, so you can analyse the classification accuracy.

Markus M

On Mon, May 10, 2010 at 10:24 AM, Sara Lucca <saretta.lucca at hotmail.it> wrote:
> Hi,
> I'm Sara and I am a ph.d student at the Politecnico di Milano with the group
> that developed the LiDAR set of commands.
> Unfortunately I'm not very found in programming but I work a lot with LiDAR
> data.
> I am not able to help on the programming side but I can help testing the
> updated command (e.g running the "new command" on LiDAR dataset that I've
> already filtered in order to evaluate differences in the
> performances/results)
> Sara
> --
> View this message in context: http://osgeo-org.1803224.n2.nabble.com/lidar-tools-update-in-grass7-tp4521505p5029463.html
> Sent from the Grass - Dev mailing list archive at Nabble.com.
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