[postgis-users] Need a method for "noding" a street network

[Nicolas Ribot]

On 10 May 2013 10:34, Sandro Santilli <strk at keybit.net> wrote:

> On Thu, May 09, 2013 at 02:53:29PM -0400, Stephen Woodbridge wrote:
> > On 5/9/2013 1:27 PM, Nicolas Ribot wrote:
> > >Steve,
> > >
> > >I modified your script to include the final step gathering all needed
> > >input lines in the results table.
> > >I also corrected the linestring ends insertion queries:
> > >
> > >...quote_ident(n_geom) || ') <> ''LINESTRING'' '; to become:
> > >...quote_ident(n_geom) || ') = ''LINESTRING'' ';
> > >
> > >which inserted null values for geom column as st_startpoint(geom) is
> > >null for any geometry <> LINESTRING.
> >
> > Duh, my bad on that and you even mentioned it. I'm pleading a nasty
> > sinus cold which has scramble my brains.
> >
> > I would like to include this in pgRouting, if that is OK with you. I
> > would also like to credit you for your effort to develop this tool,
> > so if you would like to add a comment and copyright that would be
> > great.
> >
> > >It seems to work well on bdaways dataset and costa rica highways.
> > >
> > >I will add some snapping operations as suggested by Sandro and try to
> > >see if all segments are noded.
> > >(Topology still creating after 4270 ms)
> >
> > The snapping would be nice. I'm wondering if Sandro could possible
> > use a variant of this to speed up the topology creation?
>
> Possibly. But topology building also has to setup explicit edge linking
> (which edge comes next by walking on each side of the edge) and handle
> face creation.
>
> I've actually a big refactor in mind for topology building, in that the
> current model of snapping new-comers to pre-existing primitives has a
> conceptual bug (there's no way for existing edges to be immutable).
>
> But anyway ST_CreateTopoGeo would have all input at once so shouldn't
> suffer from that bug. It'd be great if Nicolas wanted to take a look :)
> IIRC that function wasn't optimized as I tought it wasn't as useful as
> the ones building the topology incrementally... I'm pretty sure there's
> performance to squeeze out of it.
>

I Sandro,

I canceled the topology creation on costa rica dataset after 1 hour of run.
I will try with Steve dataset, which is smaller.

Nicolas

>
> --strk;
>
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