[pgrouting-users] Regarding pgrouting and postgis for shortest path

[Stephen Woodbridge]

On 1/16/2014 4:31 PM, Raghavan Krishnasamylakshmanaperumal wrote:
> Steve,
> Thanks for your reply, I think I almost understood. So you say that
> having only these GPS point may not help me I should also have the
> network map corresponding to these GPS points using which I can figure
> out the shortest path?

if you only have two point on the earth and nothing more what is the 
shortest path. "Path" implies that you have a network of paths and that 
you want to find the the shortest path within the network. If you only 
have the points and no network then you can not find the shorth path in 
the network, because you do not have one.

The way things works is that we take a point and find the nearest edge 
ot node in our network for that point and that then becomes the start or 
end point in the network. Dijkstra then searchs the network for the 
shortest path between two points.

> So right now I have only these GPS points, how should I proceed further
> to figure out the shortest path between any two GPS points from my data.

You can't do anything with just these points. You have to make them to a 
network and then search for a solution within that network.

So you have to find network data that you can use for your area of 
interest. You might look at OSM data and osm2pgrouting to load it into 
pgRouting.

You could also look into using Project-OSRM (requires 64bit HW) which is 
the router used by OSM.

> I am open to use any database/framework/language so please suggest me
> how to proceed further and I am concerned about  scalability or other
> factors because this is just a proof of concept(course project) which I
> am trying to build.

pgRouting
Project-OSRM
google: java dijkstra

There are lots of choices, but all require that you have network data.

-Steve

> Thanks,
> Raghavan
>
>
> On Thu, Jan 16, 2014 at 12:21 PM, Stephen Woodbridge
> <woodbri at swoodbridge.com <mailto:woodbri at swoodbridge.com>> wrote:
>
>     On 1/16/2014 12:46 PM, Raghavan Krishnasamylakshmanaperumal wrote:
>
>         Recently I started using PostGIS for my academic project which is a
>         route recommendation system. I have stored the data in the
>         following format.
>         /
>         /
>         /gid=>integer, activity=>varchar(20), geom geometry(Point,4326)/
>
>
>         geometry points are longitude and latitude information, for
>         example if
>         you record your Running activity using a gps device, each point
>         record
>         (longitude & latitude) is stored in the geom column.
>
>
>     The shortest distance between two points is a straight line unless
>     you want to constrain the problem to the shortest distance along
>     some road or path network.
>
>     If it is constrained to a networks of paths then you have to have
>     the data for that network available.
>
>     In the case of pgRouting, you have to load the network data and
>     prepare it for routing, then you can use you points as the start and
>     end points of a route and ask pgRouting to fins the shortest path
>     between them along the network.
>
>
>         I need to find the shortest path(using Dijkistra's) between any
>         two geom
>         points from this data set and I am trying to automate this using
>         some
>         programming language like Java.
>
>
>     With Java you can connect to the database and issue simple queries
>     to pgRouting to get your results. If you are looking for a Java
>     library to solve Dijkstra problems then this is not pgRouting. Also
>     if you are using a Java library you will still need to load the
>     network of paths that you want to solve you queries against.
>
>     Hope this helps,
>        -Steve
>
>         Please can you suggest me how to make use of pgrouting and
>         postgis data
>         to figure out the shortest path. Is there any library available to
>         automate this using Java. I am totally stuck on my project and
>         finally
>         came to know about this mailing list.
>
>
>         --
>         Thanks and Regards,
>         Raghavan KL
>
>
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> --
> Thanks and Regards,
> Raghavan KL
>
>
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