[GRASS-user] V.Select strange results

[Stefano]

Thanks all. i think that the current solution is good enough. maybe next
time i'll try the 6.5 with feature.

thanks

On Thu, May 28, 2009 at 10:39, Moritz Lennert
<mlennert at club.worldonline.be>wrote:

> On 25/05/09 18:00, Stefano wrote:
>
>> Hi all.
>> i'm looking to v.select (grass 6.4).
>>
>> i've 2 paths done by v.net.path, i want to extract the diff path of
>> these 2 paths using v.select, overlap and the reverse.
>> before this operation i clean both of them using break and snap.
>>
>> As you can see in the image there are two path, one blue and one
>> green, these two path sheared pieces (u can't see the shared path,but
>> is not imporant).
>> so, i want find the differences of these two path.
>> i do the select with a reverse command but the result is not right as
>> i can excepted.
>>
>> if u pay attention the black path (the diff path) is not completly
>> right. in fact this path has to start and finish on the intersection
>> of these two path (blue and green) but start and end before the
>> intersection. so the black path has to be identical as the green path
>> (the green path that u can see)
>>
>> i think the problem is the lines of these 2 path (green and blue) that
>> are not cut in the intersection, so the line goes across the
>> intersection of these line.
>>
>> how can i fix this problem?
>>
>
> v.select does not cut exactly at the edges of overlap, but selects the
> entire feature that overlaps, even if this feature goes beyond the overlap
> (i.e. it does an "overlap" and not an "intersect").
>
> What you want is v.overlay, but unfortunately this has never been
> implemented for two line layers (never understood why).
>
> Your best solution at this stage is to compile the current grass6 svn tree
> (6.5) with the --with-geos configure flag which will give you access to a
> much more wide array of tools than only overlap [1].
>
> Moritz
>
> [1] http://grass.osgeo.org/grass65/manuals/html65_user/v.select.html
>



-- 
Stefano
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