[Qgis-user] remove 'double' borders in polygon data

[MORREALE Jean Roc]

Le 27/05/2010 20:24, Richard Duivenvoorde a écrit :
> Hi List,
>
> I think I have a common problem:
>
> I have polygon/area data (in postgis) of let's say countries/cities.
>
> But to visualize it in a WMS with dotted lines, the borders where two
>  city polygons overlap/touch you get strange drawing effects because
> of the two dotted lines lying over each other.
>
> Now my colleague pointed to OpenJump where you apparently have: Tools
> > Edit Geometry > Convert > Extract Common Boundary Between
> Polygons...
>
> But off course this is feasible with QGIS also isn't it ?? ;-)
>
> Anybody an idea to handle this?
>
> If not: Carson, is this a new idea for fTools?
>
> TIA, Regards,
>

The easy path for you to achieve this in QGIS would be to make use of 
the grass vector format with a correct topology where 2 polygons share 
their contiguous border.