[GRASS-dev] Problems with v.net.distance

[Markus Metz]

On Mon, Jun 18, 2012 at 3:13 PM, Roberto Marzocchi
<roberto.marzocchi at gmail.com> wrote:
> Hi Markus,
>
> many thannks for your changes. I think now the command is quite O.K..
> Nevertheless I have encountered a new error:
> I have tried with the command that you suggested me (to_type is point and
> not line) and it works.
>
>
> v.net.distance input=network_cat4 output=network_cat4_distance alayer=3
> nlayer=4 afcolumn=lungh_a abcolumn=lungh_i flayer=4 from_cats=1-4 tlayer=4
> to_type=point to_cats=5-6920 --overwrite
>
> after I try to do the opposite, that is from the 6916 nodes of the network
> (that are point!) to the firestations and it don't works
>
> v.net.distance input=network_cat4 output=network_cat4_distance alayer=3
> nlayer=4 afcolumn=lungh_a abcolumn=lungh_i tlayer=4 to_cats=1-4 flayer=4
> to_type=point from_cats=5-6920 --overwrite
>
>
>
>>> Building graph...
>>> Registering arcs...
>>>  100%
>>> Flattening the graph...
>>> Graph was built
>>> ERROR: Requested feature id -1 is not reasonable(max features in vector
>>> map
>>>       <network_cat4 at ospedali_grass7>: 15747)
>
>
> I don't understand why...

Some of the 'from' features are not reachable within the network. For
each 'from' feature, the module finds the nearest 'to' feature. That
means that all 'from' features must be connected to the network, but
it is ok if some 'to' features are not connected. This is why you got
this error after you swapped the set of 'from' and 'to' features.

Fixed in r52124. But maybe a warning would be useful if some 'from' or
'to' features are not reachable.

Markus M

>
> Thanks in advanced,
> Roberto
>
> 2012/6/16 Markus Metz <markus.metz.giswork at googlemail.com>
>>
>> On Fri, Jun 15, 2012 at 6:12 PM, Roberto Marzocchi
>> <roberto.marzocchi at gmail.com> wrote:
>> > Dear all,
>> >
>> > I'm trying to use v.net.distance in grass7, which option seem be
>> > corrected
>> > respect of teh version of grass65 (alayer, nlayer and consequently
>> > costs).
>> >
>> > First of all, I noted that the option output is reported two time, but
>> > this
>> > can be simply corrected removing line 134 of main.c command. If needed I
>> > can
>> > add in the svn.
>> > Secondarly the program stop itself because if I correctly uderstand, the
>> > number of lines not corresponding with the number of nodes.
>> >
>> > ERROR: Nodes not available for line 8819
>>
>> v.net.distance should be fixed with r52069.
>>
>> >
>> > Unfortunately I'm not expert with vector grass libraries so I didn't
>> > understand the problem..
>> >
>> >
>> > --
>> >
>> > I'm using as a test the north carolina dataset and in particular I do
>> > the
>> > step of the tutorial of Trento university
>> >
>> > (http://www.ing.unitn.it/~grass/docs/tutorial_64_en/htdocs/esercitazione/network_analysis/index.html) adding
>> > also a 4th layer with the nodes. Attached a script to create the dataset
>> > (grass70)
>>
>> In the test script, use
>>
>> v.net.distance input=network_cat4 output=network_cat4_distance
>> alayer=3 nlayer=4 afcolumn=lungh_a abcolumn=lungh_i flayer=4
>> from_cats=1-4 tlayer=3 to_type=line to_cats=6-6920
>>
>> in order to get the shortest paths from the four selected firestations
>> to the network. The 'from' features are always points, I have updated
>> the description and manual accordingly.
>>
>> Markus M
>>
>> >
>> >
>> > Cheers,
>> > Roberto
>> >
>> >
>> >
>> >
>> > _______________________________________________
>> > grass-dev mailing list
>> > grass-dev at lists.osgeo.org
>> > http://lists.osgeo.org/mailman/listinfo/grass-dev
>
>