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

[achim]

Hello Daniel,

thanks you very much for helping.

> If I understand your description and image correctly, then the line
> from 1 to 4 is one single line and nodes 2 and 3 lie on it. If this is

You understand me right. I thought, you maybe knew a way, doing the
breaking of the lines at the "on line laying" points.

I thought its there is a way like "automatically(!) adding a little road
to a big one from one side (not crossing) and integrating it to the
network"?

Greetings,
Achim


PS:
The bug is in the v.edit tool=break, as I mentioned before:
breaking one selected line on a desired coordinate works well, but
selecting two or more (or all) (eg. yellow and red, point 2) breaking on
the same point, I get artifacts. This depends on the direction of the
yellow line.

(like
http://lists.osgeo.org/pipermail/grass-user/attachments/20090814/816f9568/break-0001.jpg)

If you have an idea..its welcome!
Not being in touch with the structure of the program, sadly I am not
capable of fixing the bug in acceptable time,




Daniel Bundala schrieb:

> the case then the module does not find a path from, say, 1 to 5. The
> reason is, as you mentioned in your email, that "the module runs
> successfully, but only with a network, where every line ends with the
> next node" and the module "ignores" intermediate nodes. I did not test
> it, but I think you get the same behaviour with v.net.path as well. In
> general, this is not a bug. The thing is that the line lengths/costs
> are read from a table and may represent anything and so if you know
> that the cost of traversing from 1 to 4 is X then this does not tell
> you what the cost of traversing from 1 to 2 or 2-3 should be. So to
> fix it, you need to break the lines that is, to break line 1-4 to
> lines 1-2, 2-3, 3-4.
> 
> Hope this helps,
> Daniel
> 
> On Mon, Aug 17, 2009 at 3:07 PM, achim<ak7 at jupiter.uni-freiburg.de> wrote:
>> 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
>>>> _______________________________________________
>>>> grass-user mailing list
>>>> grass-user at lists.osgeo.org
>>>> http://lists.osgeo.org/mailman/listinfo/grass-user
>>>>
>>> _______________________________________________
>>> grass-user mailing list
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