[GRASS-user] v.patch -a: how to interpret message "Line -58728 already has area/isle -1611 to left"

[Moritz Lennert]

On 20/08/18 22:09, Markus Metz wrote:
> 
> 
> On Mon, Aug 20, 2018 at 5:42 PM, Moritz Lennert 
> <mlennert at club.worldonline.be <mailto:mlennert at club.worldonline.be>> wrote:
>  >
>  > I am trying to patch together a series of vector maps, using v.patch 
> -a (apparently without -a, category values are not retained).  These 
> maps contain polygons that were extracted from the same base map (but in 
> each map there are different polygons than in the others), treated with 
> different intermediary steps, to then be all put back together in a new 
> vector map.
>  >
>  > However, for one of these maps, when I try to add it, I get:
>  >
>  > WARNING: Line -58728 already has area/isle -1611 to left
>  > ERROR: Unable to add isle (map closed, topo saved)
>  >
>  > How should I interpret this message ?
> 
> This is a problem with registering a new area. The warning is coming from
> https://trac.osgeo.org/grass/browser/grass/trunk/lib/vector/diglib/plus_area.c#L718
> and the error is coming from
> https://trac.osgeo.org/grass/browser/grass/trunk/lib/vector/Vlib/build.c#L140
> 
> Try to patch without building topology, i.e. v.patch -b, then clean with
> v.clean -c tool=bpol,break type=boundary

Will this allow to also keep the attribute tables ?

Moritz