[postgis-users] Checking Road Network Topology

[Sandro Santilli]

On Fri, Jan 23, 2015 at 10:46:43AM +0100, toni hernández wrote:
> Sandro,
> 
> At this point I am not sure. :-(
> 
> I tried again using srid=4326 and a tolerance of 0.0001 which for my
> latitud (Girona, Spain) is about 1 meter.
> This time everything worked just fine.

Great!
So, to recap, tolerance=0 errored out while tolerance=0.0001 worked fine ?

Note that when a tolerance=0 is given, the code would actually compute
the tolerance for each line geometry added looking at the smallest
representable shift from the biggest ordinate value in input.

There are known robustness issues in the topology builder which you can
find on the tracker. You might have encountered one of these. The idea
to load in chunks serves the purpose to be able to fix such issues locally
when they happen, understanding your data better and tweaking tolerances
on a feature basis (if needed).

--strk;

  ()   Free GIS & Flash consultant/developer
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