[GRASS-user] Re: grass-user Digest, Vol 50, Issue 8

[Richard Chirgwin]

Nicolas,

To and From have to be different maps - so you need to make a copy using 
g.copy.

You can then use the v.distance "all" feature - the -a flag - to create 
a database table containing a distance matrix containing all possible 
combinations of distances.

Richard Chirgwin

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> Today's Topics:
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>    1. Re: Using v.distance between two identical layers...
>       (Nicolas DEVAUX)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 03 Jun 2010 15:52:00 +0200
> From: Nicolas DEVAUX <devaux at supagro.inra.fr>
> Subject: Re: [GRASS-user] Using v.distance between two identical
> 	layers...
> To: Hamish <hamish_b at yahoo.com>
> Cc: grass-user at lists.osgeo.org
> Message-ID: <4C07B380.2080203 at supagro.inra.fr>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Hamish a écrit :
>   
>> devaux wrote:
>>   
>>     
>>> do you know if it's possible to use v.distance command when
>>> "for" and "to" layers are
>>> the same layer ?
>>> I have a layer describing ecological areas of interest and
>>> I want to qualify spatial
>>> relation between all patches. I want to identify and
>>> calculate shortest relation between
>>> all my patches boundaries.
>>>
>>> How can I do as v.distance command doesn't have any option
>>> like : eliminate identical
>>> objects from the "from" and "to" layer ?
>>>
>>> I'd like to use this particular command because of the
>>> option that create lines between
>>> nearest objects.
>>>     
>>>       
>> use g.copy or v.extract as a first step to separate/duplicate the
>> features?     
>>
>> Hamish
>>     
> g.copy will duplicate features, but will not avoid v.distance to search 
> distance between "from" layer feature to all features except itself in 
> the "to" layer. Or do you mean to do a script that isolate iteratively 
> each feature from the cover time by time (it might be very long as I 
> have a lot of features...) and use v.distance as many time as features 
> number ?
>
> Nicolas
>
>