[GRASS-user] Concave hull of a set of points (alphashapes)

Maciej Sieczka tutey at o2.pl
Sun Aug 10 03:21:18 EDT 2008

Andruit at gmx.de pisze:
> Hello,
> I have a set of points and would like to compute the concave hull of it.
> Is it possible within grass and has anybody done it before.

(Not tested idea:)

Connect all points with v.distance. Get rid of doubled lines with
v.clean tool=rmdupl. Turn lines into boundaries with v.type - this
creates areas without centroids. Add a centroid to each area. Make sure
each centroid has the same category (use v.category if needed). Dissolve
areas (v.dissolve) - you should get a single area with nodes only at the
most outer points you had in your input dataset.

Let me know if this works.


Maciej Sieczka

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