[GRASS-dev] partitioning of vector polygon?
neteler at osgeo.org
Thu Aug 30 12:44:12 PDT 2018
On Thu, Aug 16, 2018 at 6:28 PM Moritz Lennert
<mlennert at club.worldonline.be> wrote:
> On 16/08/18 17:04, Markus Neteler wrote:
> > On Thu, Aug 16, 2018 at 10:34 AM Moritz Lennert
> > <mlennert at club.worldonline.be> wrote:
> >> On 15/08/18 15:56, Anika Bettge wrote:
> >> > does anyone know how I can split a polygon into n polygons?
> >> >
> >> > For performing area image classification I need to spatially divide my
> >> > training data (points in the polygon) into spatial clumps with those I
> >> > want to train different classifiers, so that I do not need to load the
> >> > image data for the whole polygon at once in the mapset. The image area
> >> > contains 4*10^9 pixels.
> >> Maybe I don't really understand what you are trying to do, but would
> >> v.mkgrid be the solution for you ?
> > Unfortunately not: we want to split the area of interest (vector
> > polygon) into subareas.
> > It looks like this:
> > https://doc.cgal.org/latest/Partition_2/index.html
> > but with the need of specifying the number of subareas (e.g. roughly
> > of the same size).
> > The polygon may have "any" shape.
> > With v.mkgrid we may end up with tiny polygon chunks here and there.
> You could clean those in a second step with v.clean tool=rmmarea.
Yes, v.mkgrid + v.clean tool=rmarea looks like a viable approach
(along with v.report to get the polygon area in order to estimate
about the grid number of v.mkgrid).
> Otherwise, maybe the skeleton option (-s) of v.voronoi could help ?
I also tried that but...
# NC data
g.region vector=zipcodes_wake -p
v.voronoi input=zipcodes_wake output=zipcodes_wake_centerline -s
d.vect zipcodes_wake_centerline color=red
... the result is, say, complex :) Hard to topologically clean up.
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