[GRASS-dev] Large Polygon-datasets

[Stephan Holl]

Hello Radim,

On Tue, 9 May 2006 13:53:20 +0200 "Radim Blazek"
<radim.blazek at gmail.com> wrote:

> On 5/9/06, Hamish <hamish_nospam at yahoo.com> wrote:
> > > I have a very large dataset containing about 300.000 polygones
> > > which I would like to import into GRASS using v.in.ogr
> > >
> > > Is there a possibility to not build the topology during import,
> > > but afterwards. It runs nor about several hours now and does not
> > > provide more information than
> > > Importing 300000 map features...
> > >
> > > and nothing more. The maschine is very slow in response using the
> > > mouse.
> > >
> > > Does anybody have some experience in using this kind of datasets?
> > > Thanks for any suggestions how to import the data.
> >
> >
> > Yes, I have seen this and IIRC there was a Florida Coastline import
> > with the same problem.
> >
> > In all cases the polygons were all unbroken polygons with only one
> > end node breaking a single boundary line.
> >
> >
> > At the time, Radim wrote:
> > > Now I have just one idea, because the areas are probably isolated,
> > > it could be that exist one BIG boundary around all the map
> > > (I thing that something like that exists in ArcInfo),
> > > in that case, when this boundary is processed, it selects
> > > lines which could intersect it by bounding box, in that case ALL
> > > lines, and to check intersection of ALL segments of that BIG line
> > > with ALL segments of ALL other lines can take a very long time.
> >
> > I think this case is why he wrote v.split.

No this is not the case. When I apply the spatial=-switch of v.in.ogr
the module imports fine, because the area is small enough (about
100.000 polygones).

> It must go to v.in.ogr.
> v.in.ogr -c + anything != v.in.ogr

I do not understand what you mean by the above. Could you elaborate,
please?

Anyway, is there an elegant way to import large datasets even on
non-RAM-monster-maschines?

Thanks for you comments

	Stephan

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