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

[Roberto Marzocchi]

2012/6/18 Markus Metz <markus.metz.giswork a googlemail.com>

> On Mon, Jun 18, 2012 at 3:13 PM, Roberto Marzocchi
> <roberto.marzocchi a 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 a 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
>

Dear Markus,

Now It works also for other points.  Obviously the nodes not connected are
not considered.

I'm in agree with you, a warning can be very useful!

It is strange also that the points are not connected to the network. In
fact I have created the nodes using v.net.
I will check if there is any problem with v.net.

Many thanks and best regards,
Roberto






>
> >
> > Thanks in advanced,
> > Roberto
> >
> > 2012/6/16 Markus Metz <markus.metz.giswork a googlemail.com>
> >>
> >> On Fri, Jun 15, 2012 at 6:12 PM, Roberto Marzocchi
> >> <roberto.marzocchi a 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 a lists.osgeo.org
> >> > http://lists.osgeo.org/mailman/listinfo/grass-dev
> >
> >
>
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