[GRASSLIST:5333] Re: 2 prob.: v.proj and overlapping

[Radim Blazek]

ivan marchesini wrote:
> Dear users...
> I've got two problems using grass57....
> 
> the first one:
> I've an area vector map in UTM ED50 system (imported from a shp map)...
> is a complex map, with a lot of boundary segments and a lot of
> centroids... but it is quite correct because all the areas seems to
> answer correcly to v.what.vect... and all boundaries are two areas
> boundaries... according to v.digit..
> I've projected it on gauss-boaga roma40 system (an italian system) using
> v.proj...
> now only few areas are preserved...(in the gauss-boaga system I mean)
> and there are a lot of not correct boundaries (no area or 1 area... as
> v.digit explain...). Consequently, also areas are not respected ....
> can you explain me the reason of this behaviour... and how to solve the
> problem??? thank you

That is interesting. In theory, reprojection could maybe corrupt the 
topology, but it is not probable for UTM and Gauss-Boaga on a small 
area. Could you send me a small example (use v.in.region and v.select)
including both PROJ_INFO?

Radim