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

[Daniel Bundala]

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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