[GRASSLIST:5345] Re: 2 prob.: v.proj and overlapping

[Radim Blazek]

Francesco Mirabella wrote:
> Hi radim and many thanks for your reply,
> 
> no, we did not use the -c option because we thought that polygons should
> be cleaned (or maybe not?)

That is correct, v.in.ogr which -c does not import polygons correctly.

The proble is surely in import, but I cann say what is the problem
untill I see that data. Can you send me a _small_ subset of your
dat (shp) ideally just few areas?

Radim


> Francesco
> 
> On Thu, Jan 13, 2005 at 04:04:53PM +0100, Radim Blazek wrote:
> 
>>Have you used v.in.ogr -c?
>>
>>Radim
>>
>>Francesco Mirabella wrote:
>>
>>>Hi Radim and all,
>>>
>>>I am currently working with ivan regarding the topic of this message:
>>>
>>>Actually, we had some problems when reprojecting from UTM to
>>>Gauss-Boaga as Ivan wrote before. The original map was Corinne landcover
>>>2000 (.shp).
>>>The problem first arised after reprojection to Gauss-Boaga so we decided
>>>to go back to the originally imported map into UTM (corinne landcover
>>>2000 is utm).
>>>
>>>The original UTM corinne was displayed well also when queried 
>>>(d.what.vect), but when looking into it in detail with v.digit we found
>>>that a lot of boundaries were duplicated. It means that each vertex snapped
>>>over another of the same boundary, closing where the boundary start (the
>>>start and the end of the boundary is the same!!! and also all the other
>>>nodes).
>>>This brings to the creation of a lot of doubled areas and their centroids 
>>>are positionated exaclty over the double boundary...
>>>
>>>To try to solve this, we decided to try to delete the double areas and
>>>tried v.clean tool=rmarea thresh=es.1(meter) in order to have the small 
>>>double areas removed.
>>>
>>>Now the problem is that v.clean was still removing areas on the map but 
>>>the process is still running after 15 hours work on a pentium 4 processor, 
>>>512 Mb ram!
>>>
>>>many thanks for your help
>>>
>>>Francesco
>>>
>>>
>>>
>>>On Thu, Jan 13, 2005 at 12:09:23PM +0100, Radim Blazek wrote:
>>>
>>>
>>>>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
>>>>
>>>
>>>
>