[pgrouting-users] Test case - can't find route

[Stephen Woodbridge]

Hi Hugo,

I have not been able to load this test case up yet, but my intuition is 
that the topology is a problem as you suggest. Can you post the results 
of this query and what tolerance did you use with assign_vertex_id();

select gid, source, target, x1, y1, x2, y2 from roads;

Tolerance needs to be set to a value in the unit of the coordinate 
system you are using for your edges. So if you are using degrees thena 
reasonable tolerance= 0.000001 if you are use 6 decimals of precision. 
Or if your data is in meters or feet then 1.0 might be appropriate. 
Basically the tolerance is the maximum distance between two end points 
that you want to be considered as the same point.

-Steve

On 5/11/2012 4:27 AM, Hugo wrote:
> Hello all,
>
> I've been using the same workshop to try out pgrouting. And i have also
> tried with the a-star algorithm which is giving the same results. Here
> are the queries i'0ve tried:
>
> select * from shortest_path_astar(
> 'select gid as id,
>      source::integer,
>      target::integer,
>      length::double precision as cost,
>      length::double precision as reverse_cost,
>      x1, y1, x2, y2
>      from roads',
>      8, 5, true, true
> )
>
> select * from shortest_path(
> 'select gid as id,
>      source::integer,
>      target::integer,
>      length::double precision as cost,
>      length::double precision as reverse_cost
>      from roads',
>      8, 5, true, true
> )
>
>  From what i was able to check, i thiink this might be related with the
> topology that is built with the function assign_vertex_id() but i'm
> really not sure. I think i will try to explode the road network into
> simple lines (having only two points defining each line) and try it out
> again to see if that makes any changes.
>
> Any addiotional hints?
> Cheers,
>
> Hugo
>
> On Fri, May 11, 2012 at 7:21 AM, Javier Mr <javiersdevmail at ymail.com
> <mailto:javiersdevmail at ymail.com>> wrote:
>
>     Hi,
>
>     i would sugest using A-Star algorithm (specially form large
>     datasets). As Daniel has said the query would be very usefull. Check
>     the directed graph and has_reverse_cost booleans parameters in the
>     core query. Just in case this is a link to a workshop, the one i
>     used to get pgrouting up and running:
>     http://workshop.pgrouting.org/chapters/shortest_path.html#dijkstra
>
>     Regards.
>     Javier
>
>         *De:* Daniel Kastl <daniel at georepublic.de
>         <mailto:daniel at georepublic.de>>
>         *Para:* pgRouting users mailing list
>         <pgrouting-users at lists.osgeo.org
>         <mailto:pgrouting-users at lists.osgeo.org>>
>         *Enviado:* Viernes 11 de Mayo de 2012 1:23
>         *Asunto:* Re: [pgrouting-users] Test case - can't find route
>
>         Hello Hugo,
>
>         Thank you for reporting this!
>         Could you also share your query?
>
>         Daniel
>
>
>         On Fri, May 11, 2012 at 2:32 AM, Hugo <hfpmartins at gmail.com
>         <mailto:hfpmartins at gmail.com>> wrote:
>
>             Hello all,
>
>             This is my first post to this mailing list as i have just
>             started to look into pgrouting more deeply.
>             When making some routing with this fantastic piece of work,
>             on a big network i was able to find some porblems where
>             pgrouting is not finding any route. I attach a very simple
>             and small data set (roads and vertices_tmp as shapefiles)
>             that illustrates the problem. If you look into teh image
>               below, pgrouting is not able to calculate route between
>             point 8 and 5. I'm using the Dijkstra algorithm and have
>             built the topology as explained in the docs. I'm using
>             pgrouting 1.0.3 under postgres 8.4 with postgis 1.5. What to
>             do in the topology so that a route can be found and how can
>             i do it in a bulk form to apply to a much bigger roads dataset?
>
>             Thanks in advance. Cheers,
>             Hugo
>             Inline image 1
>             --
>             Hugo Martins
>
>
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>
>
>
>         --
>         Georepublic UG & Georepublic Japan
>         eMail: daniel.kastl at georepublic.de
>         <mailto:daniel.kastl at georepublic.de>
>         Web: http://georepublic.de <http://georepublic.de/>
>
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>
> --
> Hugo Martins
>
>
>
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