[GRASS-user] visited lines

[Annalisa Minelli]

Hello Moritz,
I tried your solution and since I generated the path using the same
v.net.path with the same -s flag (which preserves the segments) that you
suggest, when I do the v.distance trying to "copy" the attribute cat from
the net segments it seems not to work properly - I mean, it copies
"something" but that "something" is wrong in the sense that it takes the
category of the element NEAR the studied one, not 'under' even specifying a
dmax=0..

v.net.path input='gridCat' output='tmpPath2' file='tmpCoord2' -s
v.db.droptable map='tmpPath2' -f
v.category input='tmpPath2' output='tmpPath4a' option='del'
v.category input='tmpPath4a' output='tmpPath2' option='add')
v.db.addtable map='tmpPath2' columns='cat integer,tmpcat integer'
v.distance from='tmpPath2' from_type='line' to='gridCat' to_type='line'
upload='cat' column='tmpcat' dmax=0

here a pic of my situation: http://oi62.tinypic.com/2epopcj.jpg
in red the tmpPath2 and tmpcat value as label
in black the gridCat and the value of the category as label

Thanks for all,
Annalisa

ps. ..and for the request too :)




2014-03-24 17:10 GMT+01:00 Moritz Lennert <mlennert at club.worldonline.be>:

> On 20/03/14 11:41, Annalisa Minelli wrote:
>
>> Hi list,
>> I have a maybe stupid question, but I should identify (by category) the
>> net lines visited from going to one point to another along a net. I
>> tried the v.net <http://v.net> module, but I'm not colpletely sure to
>>
>> have understood what the 'nreport' option for the parameter 'operation'
>> does.
>> I don't necessarily need to generate the path, I should only identify
>> the visited lines by printing category..
>>
>
>
> I don't think there is a direct way of doing this (except possibly by
> activating debugging and then filtering out the relevant info), but you can
> do it through a combination of v.net.path, v.category and v.distance. E.g.
> (using the North Carolina demo dataset):
>
> v.net -s streets_wake points=schools_wake out=network op=connect
> thresh=500
> echo "1 166 1" | v.net.path -s network out=mypath
> #The result is a map with the same category value for all segments, but we
> need different category values for each segment
>
> v.category mypath op=del out=temp
> v.category -t temp op=add out=mypath_segs
>
> v.distance -p from=mypath_segs to=network upload=cat col=segcat
>
> #The result should be (I didn't verify) the list of the cat values of the
> lines in network that the path goes through.
> #If you need another attribute of these lines, just use upload=attr and
> tocolumn= in the v.distance call.
>
> Moritz
>
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