[GRASS-user] how to clean vector file after reprojection

Moritz Lennert mlennert at club.worldonline.be
Wed Feb 7 09:22:52 EST 2007

On 07/02/07 00:31, Hamish wrote:
> Moritz Lennert wrote:
>> I am trying to (inverse) project a vector file from an laea location
>> to a lat-long location.
> ..
>> 2) Which tool (v.clean ?) could I use to solve this ?
> Yes, try "v.clean tool=snap". Or before reprojection "v.clean
> tool=break".

'break' on the source map does not find any intersections to break.

'snap' on target map (v.clean in=nuts2 out=nuts2_snap_0_001 tool=snap 
thresh=0.001 - which if I calculated correctly should snap anything 
within a bit more than 100 meters) gives me an even worse result (even 
less areas are recognized):


> My guess is lines are not broken at intersections and reprojected lines
> no longer exactly touch? (only verticies are projected)

Yes, that is the problem. I had mistakenly assumed that an end of line 
automatically is a 'node' and that unclosed lines would show up as 
one-line nodes. But I see that unclosed ends of lines are not nodes and 
are, therefore not visible in v.digit...

But, really strange: looking at the same spot in the source map, the 
line also is not closed, but is still recognized as an area... ???

Will have to explore this some more.


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