[pgrouting-users] Checking Network Validity (was "Nasty Crash")

Richard Marsden winwaed at gmail.com
Wed Feb 2 10:11:04 EST 2011


Well with the ice storm, the hard disk that should have arrived today, has
been delayed. So updating to an Ubuntu system with the latest pgRouting is
going to have to wait.

I've been trying to clean up my road network, but I'm still getting the
crash.
My data is the entire planet.osm OpenStreetMaps dataset loaded into PostGIS
using osm2po.

It seems there isn't a way to determine what the problem is, other than
going through a list of possible network problems (and using the latest
pgRouting).
Here are the problems I have thought of:

- Zero costs or very short lengths
I do not have negative costs or lengths.
I did have some zero costs and lengths, so I have updated my view to set
these to my geography lengths (previously I used geometry lengths, but with
global data I don't think this is a good idea as it will cause problems with
routes that cross a wide range of latitudes (eg. Chile, Russia, or Canada).
Of course using geography lengths is currently very slow, but this can be
cached in its own column.

I'm using the dijkstra__sp_delta() function. If I understand correctly, this
requires length, cost, and reverse cost fields?
And I should set these to the same (which is what I'm doing)?

The geography lengths mean I no longer have any zero costs, but I do have
48,000 links which are less than a metre, and 1,376 links which are less
than 0.1metres.
Then I can remove all nodes which are within 1m of another node. I think I
will require a Python script to do this, as it will require renumbering.
(I'm actually thinking of creating a copy of my link table that I can modify
without losing my original table)

- I don't have any links which start and stop at the same node.
Due to my intended application, closed loops can be removed if I do find
them.

- High node identifier values
I have heard of problems with high node identifiers. What exactly is "too
high"?
As I'm using the entire planet.osm, I am going to have a huge number of
nodes. So high node identifiers seem like they might be a problem?

Are there any other problems I should look for?


Richard
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