[GRASS5] counting number of vector points in same position?

Michael Barton michael.barton at asu.edu
Tue Aug 16 11:25:26 EDT 2005

Thanks Radim. This is  helpful. This is also the first example I've seen of
the query option for v.to.db.

Could you explain how it works in a bit more detail.

Michael Barton, Professor of Anthropology
School of Human Evolution and Social Change
Arizona State University
Tempe, AZ  85287-2402

voice: 480-965-6262; fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton

> From: Radim Blazek <radim.blazek at gmail.com>
> Date: Tue, 16 Aug 2005 10:36:23 +0200
> To: grass5 developers list <grass5 at grass.itc.it>
> Subject: Re: [GRASS5] counting number of vector points in same position?
> 1) v.clean rmdupl will remove duplicates and it should attache
>     all cats to one point (-> one-many link between geometry and attributes)
> 2) v.category layer=2 (-> new layer with 1 cat/point)
> 3) create and link new table to layer 2
> 4) v.to.db option=query layer=2 qlayer=1
>     (query attributes in layer 1 and uppload to layer 2)
> Radim
> On 8/10/05, Markus Neteler <neteler at itc.it> wrote:
>> Hi,
>> I have to transform a vector points map of disease reports.
>> Often more than one report falls into the same location as
>> reports were done/geocoded based on cities. This results into
>> a vector map with often several vector falling into the
>> same coodinate pair.
>> I have to transform this map into a new vector map with
>> single point per coordinate pair and number of cases as
>> attribute.
>> How to do that?
>> I was thinking of v.distance -a to calculate zero-distances.
>> This requires to exclude that the points "see" themselves.
>> But then, I am not sure how to transform this into a map.
>> Maybe with some SQL fun (distinct() operator or so)?
>> Suggestions welcome. This functionality appears to me to
>> be needed for GRASS. I darkly remember that it was asked
>> time ago, but cannot find the mail(s).
>> Thanks
>>  Markus
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