[pgrouting-users] Regarding pgrouting and postgis for shortest path
Stephen Woodbridge
woodbri at swoodbridge.com
Thu Jan 16 14:11:23 PST 2014
On 1/16/2014 4:54 PM, Raghavan Krishnasamylakshmanaperumal wrote:
> Steve,
> Thanks for pointing out various resources, probably I didn't explain
> about my data properly. So the data which I have is not just two points,
> I have collected data from my and some of my friend's runkeeper
> <http://runkeeper.com/> GPS traces for various activities like running,
> walking, biking in and around Chicago. I have all these GPS
> points(longitude,latitude) information with me. What I am trying to find
> is the shortest path given any two points from the data which I have
> collected.
Then you should be able to:
1. load the track points into a table
2. convert the tracks into linestrings
3. then run pgr_nodenetwork
4. update the resulting table to include costs or lengths
5. then run pgr_createTopology
6. then map a start point and end point to the network nodes
7. call pgr_dijkstra to get shortest path
All of the above happens in the database
8. write a client application the connects to the database maps the
start and end points, computes the path and displays it or whatever you
need to do with it.
-Steve
> Thanks,
> Raghavan
>
>
> On Thu, Jan 16, 2014 at 3:42 PM, Stephen Woodbridge
> <woodbri at swoodbridge.com <mailto:woodbri at swoodbridge.com>> wrote:
>
> 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>
> <mailto: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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> Thanks and Regards,
> Raghavan KL
>
>
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