[GRASS-user] shortest distance within a points layer
mlennert at club.worldonline.be
Mon Aug 11 07:57:18 EDT 2008
On 11/08/08 12:49, G. Allegri wrote:
> It means that I have to select shortest distances from the distance
> matrix from outside GRASS (because I can't use MIN, GROUP BY, and
> similar statements with db.select with DBF driver), and then update
> somehow the points attrbitutes from the previous selection... Mmm,
> it's quite a common task, there should be something more
Well, if you move to sqlite (which will be the default in the future),
the task becomes pretty straightforward...
But maybe we can look into adding a minimum threshold to v.distance
(i.e. only record distances above a certain threshold).
> 2008/8/11 Alex Mandel <tech_dev at wildintellect.com>:
>> G. Allegri wrote:
>>> Hi lis
>>> I need to evaluate the shortest distance between the points of the same
>>> layer .
>>> v.distance fails as to_map and from_map overlap (every shortest
>>> distance is obviously 0: from point to itself). I was considering the
>>> use of network analysis tools... but I don't see a straigthforward way
>>> with them.
>> How about v.distance -a which creates a distance matrix then you can query
>> the table for lowest value, group by point and exclude distances of 0.
>> see http://www.grass.itc.it/gdp/html_grass63/v.distance.html
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