[GRASS-user] Multiple v.net.path parameters

[achim]

Hello Daniel (and others),

I ran the module successfully, but only with a network, where every line
ends with the next node.

In attached example it is possible to calc path from 1 to 4 and from 5
to 6, but not from 1 to 2,3,5,6 or from 5 to anywhere expect 6 and so on.

Do you have an idea how to handle this?

Especially: do you know if "breaking the lines" (eg. dark green one at
point 5) is possible with networking techniques?

Sorry for asking you directly, but I hopefully thought you are deep
inside the topic at the moment.

Thanks anyway for your work!
Achim



Daniel Bundala schrieb

> Hello all,
> 
> I have finished v.net.distance module as a part of my Google Summer of
> Code project. The (source code of) module can be downloaded from grass
> add-ons repository (vector/net.analyze). I recommend to download the
> entire directory to avoid any compilation issues. Additionally, you
> get an access to some latest network analysis modules! Anyway, simple
> make command in the net.analyze directory should compile the modules
> (and library). There is no documentation (yet), however, the interface
> should be similar to the one used in v.net.path and/or v.distance.
> Finally, here is a couple of nice pictures:
> 
> http://people.ksp.sk/~dano/grass/nd.png
> http://people.ksp.sk/~dano/grass/ndt.png
> http://people.ksp.sk/~dano/grass/ndtd.png
> 
> Blue and orange lines show the shortest length and time paths respectively.
> 
> Best,
> Daniel
> 
> On Wed, Jul 1, 2009 at 5:56 PM, Moritz
> Lennert<mlennert at club.worldonline.be> wrote:
>> On 01/07/09 04:44, J. Holden wrote:
>>> Hello,
>>>
>>> I am looking to use v.net.path to determine the distance of many
>>> different points to many different other points on a network.
>>>
>>> Is it possible to send multiple parameters to v.net.path? For
>>> instance, I have (in theory) 4 points connected to a network. I want
>>> to find the distance of the line segments between points 1 and 4, 2
>>> and 4, & 3 and 4.
>>>
>>> I want to: run v.net.path once by passing multiple parameters; get
>>> vector line output of each of these three paths found by v.net.path
>>> in one output file; calculate the distance of each line from the file
>>> using v.to.db.
>>>
>>> Since this is not a module of GRASS which I have worked with in the
>>> past, I am wondering if this is possible.
>> Sure, as mentioned on the man page:
>>
>> "Nodes can be piped into the program from file or from stdin. The syntax is
>> as follows:
>>
>> id start_point_category end_point_category
>>
>> or
>>
>> id start_point_x start_point_y end_point_x end_point_y"
>>
>>
>> So to take your example, and assuming that 1,2,3,4 are category values of
>> existing points:
>>
>> Create a file containing:
>>
>> 1 1 4
>> 2 2 4
>> 3 3 4
>>
>> and feed it to v.net.path with the file= parameter.
>>
>> You will then get one vector map with severals lines which have the category
>> values used in the first column of your file.
>>
>> Moritz
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