[Gvsig_english] "bleeding" polygon themes and how to repair them

[Benjamin Ducke]

Well, there was talk about a topology extensions on this list a day
or two ago. As it stands, OpenJUMP has pretty good tools for
cleaning/checking geometries.

Ben

----- Original Message -----
From: "Wolfgang Qual" <wolfgang.qual at gmx.net>
To: "gvsig internacional" <gvsig_internacional at runas.cap.gva.es>
Sent: Tuesday, October 28, 2008 4:33:21 PM (GMT) Europe/London
Subject: Re: [Gvsig_english] "bleeding" polygon themes and how to repair them

Hello Micha,
thanks for your hint. Therefore, the shapefile does not seem to be broken only 
drawn in a differnt way? However, it happens sometimes that a shapefile 
really contains broken geometries. A function to check this within gvSIG 
would be great - do you know an open source application that could do that 
job?

Best,
Wolfgang


Am Dienstag 28 Oktober 2008 15:40:53 schrieb Micha Silver:
> Wolfgang Qual wrote:
> > Dear developers,
> > I think you know that problem: a polygon theme has some polygons those
> > boundary is not perfectly closed. Thus, when opening that layer, the
> > polygon "bleeds to death" - the whole view gets coloured.
> > Well, I just had this to happen - in ArcView 3.2.
>
> I believe that the shapefile spec requires that area shapes be created
> in a clockwise direction. So that as you "walk" around the area, inside
> is always to your right.
> If an area is created in reverse (by GPS or digitizing) then in Arcview
> 3.2 you'll see the whole map colored, as you described.
>
> Sometimes you can fix badly made shapes by just saving as a new
> shapefile. In addition there are some shapefile repair tools out there
> that will sometimes overcome this problem.
>
>
> Good luck...
> Micha
>
> > When opening the same layer in gvSIG, nothing happened. This is strange,
> > isn't it? Is the vector layer defect or not?
> > Now, I am in a "catch 22" situation: which program is telling a lie?
> > gvSIG's or ArcView (you will say "AV of course", grinning... )
> > In order to find out the truth, I would like to ask you, whether gvSIG
> > will provide once a possibility to find out defect geometries. It would
> > be really great, if such a tool would be available in the future. This
> > tool would be even better, if it would not just repair a layer, but
> > (before) tell the user where the problems lie (for example by selecting
> > the defect polygons graphically). Otherwise, everything is a blackbox to
> > me.
> >
> > All the best,
> > Wolfgang
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> >
> >
> >
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