[GRASS-user] ... getting rid of duplicate polygons ...

[Huidae Cho]

Uwe,

It wouldn't be easy to tell what your problem is without seeing your
dataset. If you don't want to share your dataset, maybe create a small
subset of it so others can try it.

Regards,
Huidae

On Fri, Feb 10, 2017 at 11:44 AM, Uwe Fischer <gisfisch at t-online.de> wrote:

> Hello list,
>
>
>
> I have a question about dealing with duplicate polygons (dp) coming into
> GRASS from a polygon shapefile. The polygons are not overlapping or having
> gaps, but there are a number of real duplicate ones (polygons show parcels
> with owners, and if one parcel has two or more owners, e. g. wife and
> husband, this situation in the shapefile is represented by two identical
> polys with two database rows that only differ in the owners name).
>
>
>
> My goal is to get rid of duplicates, having a result with only one
> polygon/centroid at a given location with only one owner name. The name
> does not matter, it can be chosen arbitrary by the system. This works fine
> when using ESRI "clean"-command. The structure of the database table is
> maintained while one (or many) of the dp is/are lost, leaving only one
> valid polygon.
>
>
>
> Now, I found an older thread called "unable to get rid of duplicate
> polygons". Obviously, the problem/question is the same but I could not find
> a solution for GRASS there. So I tried:
>
>
>
> v.clean -c input=input at mapset output=output_clean tool=snap,rmdac,bpol
> threshold=0.01,0,0
>
>
>
> and
>
>
>
> v.clean -c input=input at mapset output=output_clean
> tool=break,snap,rmdupl,rmdac,bpol
>
>
>
> Nothing did work. I get a map with tree layers, one showing the islands
> only (layer 0), one showing the complete polygon set with duplicates (1),
> and one showing only the duplicates (2). I also tried to delete layer 2,
> assuming that this might remove the dp, but it only messed up the dataset.
>
>
>
> What am I doing wrong?
>
>
>
> Regards, Uwe
>
>
>
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