[GRASS-user] Determining number of overlapping features per location after import of shape file

[Markus Neteler]

Rainer,

I suggest to try the snap parameters of v.in.ogr first. Maybe the SHAPE
file is full of gaps and slivers (commonly found, even in governmental
data).
*Small* snapping values might cure it. Be careful to not snap, say,
Africa to a triangle :)

Markus

On Mon, Jun 23, 2008 at 12:13 PM, Rainer M Krug <r.m.krug at gmail.com> wrote:

> Hi
>
> I am importing a vector layer from a shape file as follow, and get the
> warning below:
>
> > v.in.ogr  dsn=/home/rkrug/Documents/Projects/AlienSpread/data/input/
> layer=fireHistory output=fireHistory --overwrite
>
>
> WARNING: 703 areas represent more (overlapping) features, because polygons
>         overlap in input layer(s). Such areas are linked to more than 1
>         row in attribute table. The number of features for those areas is
>         stored as category in layer 2
>
>
> I am aware of that, and I want to create a raster layer with the
> number of features overlapping in each location. As I ultimately need
> a raster layer, I thought to use the following, but I get the error
> message below:
>
> > v.to.rast  input=fireHistory layer=2 output=mf use=attr column=category
> --overwrite
>
> ERROR: Unable to get layer info for vector map
>
> Why is that?
>
> Is there another way of getting the number of overlapping features per
> cell?
>
> Thanks
>
> Rainer
>
>
> --
> Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
> Biology, UCT), Dipl. Phys. (Germany)
>
> Plant Conservation Unit
> Department of Botany
> University of Cape Town
> Rondebosch 7701
> South Africa
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