[GRASS-user] v.overlay missing polygon

[Vincent Bain]

Falko,
if you try to make things match, looks like v.overlay returns a correct
result. Try the following command -- threshold 5 m is arbitrary, of
course :

v.edit map=plot type=boundary tool=move move=0,0 thresh=-1,5,0 bgmap=veg
snap=vertex bbox=3607160,5733860,3609000,57350

then 
v.overlay --o ainput=veg atype=area binput=plot btype=area
output=res_overlay operator=and

(right now, I can't tell you what was wrong for the long western
polygon)

Vincent.



Le mardi 13 mars 2012 à 11:41 +1100, Richard Chirgwin a écrit :
> On 13/03/12 6:36 AM, grass-user-request at lists.osgeo.org wrote:
> > Dear Vincent,
> >
> > thanks for your idea. I wasn't aware of the possibility to snap a vector
> > map to another one. Good thing to know!
> > However, it didn't solve my problem.
> > Actually, I checked the data with respect to my theory 2 again, and I
> > must say: Visually it seems, that in this case the two data sets I would
> > like to overlay match perfectly concerning the boundaries. The theory
> > might be wrong.
> >
> >
> > I did some further testing:
> >
> > Even if I isolate the polygon that disappears in the overlay process
> >
> > v.extract input=veg output=veg_137 list=137
> >
> > and use it for the overlay
> >
> > v.overlay ainput=plot atype=area binput=veg_137 btype=area operator=and
> > output=res_137_and
> >
> > the result is erroneous. Nothing new, but still very strange.
> >
> >
> > Tricky. I am puzzled and need to get home;-)
> >
> > Falko
> Falko,
> 
> I agree - the same error reproduces for me, using your vectors.
> 
> Neither veg nor plot show any apparent errors in v.digit.
> 
> Anyone offer suggestions to try and debug this?
> 
> Richard
> 
> 
> 
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