[GRASS-user] Count points in a network between two locations

[Markus Metz]

On Sat, Feb 2, 2013 at 12:51 PM, Moritz Lennert
<mlennert at club.worldonline.be> wrote:
> On 01/02/13 19:55, Markus Metz wrote:
>>
>> On Fri, Feb 1, 2013 at 6:39 PM, Moritz Lennert
>> <mlennert at club.worldonline.be>  wrote:
>>>
>>> On 01/02/13 11:44, Johannes Radinger wrote:
>>>
>>>
>>>>    the problem is that the v.net.allpairs lines are partly
>>>> overlapping (sharing parts). So there
>>>> are several barriers on partly overlapping lines, but I want to select
>>>> all barriers per line category.
>>>
>>>
>>>
>>>
>>> IIUC v.net.allpairs actually creates several duplicate segments which
>>> seems
>>> contrary to GRASS topology rules.
>>
>>
>> GRASS topology supports overlapping lines.
>
>
> Yes, but having several overlapping line segments that are actually the
> representation of the exact same path kind of seems against the idea of not
> duplicating information if not necessary.
>
>
>>
>>> Shouldn't these rather be represented by
>>> single segments with multiple category values (like v.buffer in grass7) ?
>>
>>
>> Yes, but only if the segment directions are also identical. For
>> example, if backward direction costs are identical to forward
>> direction costs, the path from node A to node B is a duplicate of the
>> path from node B to node A, but in reverse direction.
>
>
> Right, didn't think about direction here. I was more thinking about the
> situation where paths from A to B, C, D, E all have a common part before
> forking to the respective destination later on.
>
> But I guess even for this situation overlapping lines are not so much of an
> evil to justify making this into an issue.

Fixed in r54893.

Markus M