[pgrouting-users] Shortest Route Search Not Working

[Daniel Kastl]

Hi Dan,

A* and Shooting* have a heuristic component and prefer to move towards the
goal. It's an assumption to make shortest path search faster, though usually
data loading time takes a lot longer than path calculation. You usually
don't see a (big) difference.
You can send me some data and I can take a look.

Daniel


2010/7/18 Dan Putler <putler at yahoo.com>

> Hi Daniel,
>
> To follow on Yasir's comments in terms of routing results, I've been
> working with a simple example data set where the distance and travel time
> results are likely to be different (really there are several equally good
> routes based on distance, but a unique route based on travel time, but with
> the "length" field in the database reflecting travel time along an edge).
> When doing the routing based on travel time I get the correct solution using
> the Dijkstra algorithm, but an incorrect result using the A* and Shooting
> Star algorithms. The nature of the errors I'm getting would be consistent
> with what Yasir is finding. I'd be glad to send you both the network data
> and my test queries. I'm running on 64bit Ubuntu 10.04 using the Ubuntu
> repository version of PostgreSQL (8.4.4), PostGIS 1.5.1, and built pgRouting
> from the subversion repository on Tuesday.
>
> Dan
>
> --- On Fri, 7/16/10, Daniel Kastl <daniel.kastl at georepublic.de> wrote:
>
> From: Daniel Kastl <daniel.kastl at georepublic.de>
> Subject: Re: [pgrouting-users] Shortest Route Search Not Working
> To: pgrouting-users at lists.osgeo.org
> Received: Friday, July 16, 2010, 9:58 PM
>
>  I hope you don't mind helping me with another couple short questions:
> 1. Projection 4326 with latlng is lot easier for me to work with. Although
> there are ways to convert the latlng to
>  900913 projection, I was wondering how would I be able to directly use
> 4326 and run search on it (HTML changes), assuming that the tiles were
> generated with 900913 projection and the routing database is set to 4326?
>
>
>
> You can use Postgis "transform()" function to do this:
> http://postgis.refractions.net/docs/ST_Transform.html
>
>
>
> 2. Just out of curiosity.
> The routing results usually take residential route ways, instead of taking
> instead of taking highway streets (which is more like what results from
> Google Maps show). Any ideas why the difference?
>
>
>
> pgRouting gives you the "shortest" path and it's up to you to define what
> is "shortest". Easiest is to take length as cost, but if you take time as
> cost, then shortest will be the fastest. You could for example define some
> speed for your road classes, and if the speed is higher on highways it will
> prefer the highway like Google Maps does.
>
>
> Daniel
>
>
> Thanks
>
>
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