[GRASS-dev] point cloud analysis: new features

[Markus Metz]

On Fri, Jan 9, 2015 at 11:45 AM, Benjamin Ducke <benducke at fastmail.fm> wrote:
> On 08/01/15 23:46, Markus Metz wrote:
>
> [..]
>
>>> Thanks Markus, this is excellent progress.
>>> It seems to me that the approximation of cluster shapes from grouped
>>> points is a generic problem that would best be solved with a separate
>>> module. As long as the shapes are roughly convex, the existing v.hull
>>> should work fine. For concave shapes, AFAIK things become messy because
>>> common methods such as alpha shapes require the user to provide
>>> threshold values.
>>
>> This is true, but v.concave.hull [0] could help ;-)
>>
>> Markus M
>>
>> [0] https://trac.osgeo.org/grass/browser/grass-addons/grass7/vector/v.concave.hull
>>
>
> Wow. And it's been there for a while. How could I not see that?
> I think it's high time that I switch from GRASS 6 to 7.

Indeed.

>
> Nevertheless, since you did all that work on v.cluster in GRASS 6,
> maybe it would be worth implementing this:

v.cluster exists only in GRASS 7.1. It can not even be backported ti
GRASS 7.0 because it relies on a new (new to GRASS) spatial index that
is only available in GRASS 7.1.

>
> http://grasswiki.osgeo.org/wiki/Create_concave_hull
>
> ... in a GRASS 6 shell script?

If you know Python and shell scripting, translating v.concave.hull to
a shell script is easy. Otherwise, chances are good that the Python
script v.concave.hull also runs with GRASS 6. Maybe some option names
need to be modified.

Markus M

>
> I am looking forward to trying the new clustering algorithms,
> especially "density" and "optics2"
>
> Many thanks,
>
> Ben
>
>
> --
> Dr. Benjamin Ducke
> {*} Geospatial Consultant
> {*} GIS Developer
>
> Spatial technology for the masses, not the classes:
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