[RouterGeocoder] FW: [OSGeo-Discuss] Discussion on Routing

[Andrew Ross]

FWD for history on the new list 

-----Original Message-----
From: discuss-bounces at lists.osgeo.org
[mailto:discuss-bounces at lists.osgeo.org] On Behalf Of Stephen Woodbridge
Sent: November 11, 2008 1:20 PM
To: OSGeo Discussions
Subject: [OSGeo-Discuss] Discussion on Routing

(Orkney)Toru Mori wrote:

[snip]

> p.s. Anybody want to talk about routing?

[changing subject line was: RE: [OSGeo-Discuss] Anyone interested in
geocoding and routing?]

I have started playing with pgRouting and find it to be an impressive start.
It was easy to rewrite some of the plpgsql wrappers to better suit my needs.
I was able to write a driving directions module the explicates the direction
as text and can be configured for multiple languages.

There are a few limitation that I see:

1) poor support for turn restrictions. It supports turn restrictions but if
you want to enter multiple restrictions at a given intersection it is
difficult to do and not intuitive. I have updated a couple of the wiki pages
to add more information. This is really needed to be able to support
commercial datasets like Navteq.

2) There is no way to optimize fetching of data that is needed for a
potential solution other than via the postGIS spatial index which is based
on bounding boxes. This is very bad for route that follows basically a 45
degree diagonal path. Another option would be to organize data into squares
of a fixed spatial size, these could be loaded and cached as needed.

3) The data for the US and Canada or all of Europe has in the ballpark about
27-32 million segments. I would like to see optimization like the above,
and/or support for multilevel routing as an option.

3a) There is also some very new research that has been done gives 2+ orders
of magnitude faster routing by doing some preprocessing of the network. It
might be nice to see something like this integrated.
http://algo2.iti.uni-karlsruhe.de/english/routeplanning.php

4) I would like to see a decoupling of the routing engine from the backing
stores to support it. PostGIS is nice and I'm happy to work with it, but I
can see a lot of situations where not using postgresql could be desirable.
It would be nice to have an API that would allow plugable or code-able back
end data stores.

5) It would be nice to have the ability to set some standard costs like it
cost more to make a turn across traffic than with traffic. It costs more to
make a turn than to stay on a street, so the cost of the turn must add value
to the overall route. This helps to avoid the stair-step routes in a gridded
city region. The USPS has save millions of dollars in fuel costs by avoiding
left hand turns across traffic unless it is absolutely required.
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