[GRASS-user] isoareas from DEM data

[Hamish]

Stefan Eriksson wrote:
> > > I am trying to create isoareas from DEM data.
> > > So far I have managed to create the polygons from DEM data by
> > >> r.mapcalc "newElev2 = round(elevation.dem / 100) * 100"
> > >  100%
> > >> r.to.vect

Moritz Lennert wrote:
> > Have you tried r.contour ?

Stefan Eriksson wrote:
> Yes, but I want polygons rather than lines as output. r.contour only
> produce lines, does it not?

Convert lines to polygons with 'v.type line,boundary' and v.centroids.

Areas in GRASS are virtual features made from boundaries + centroids.
The centroid will typically hold the attribute data (like elevation range) and
the boundary will not have a category (it is ambiguous as to which area
touching the boundary belongs to the attribute. Note that many GRASS vector
modules only work on features with category numbers, add/remove those with
v.category.


Hamish



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