Re: [Geotools-gt2-users] LineString Graph Traversal

[Satyanarayana Murty Pindiproli]

 
Hi jason,
Considering your Queries I think you have just begun the Work.
here is Somehting that i can Help you out with.
Do U want to Load the Graph Network at all times and Create a route for
Points A and B ?

This is the most Optimum way of Doing that cause ur Data Change would be minimum and Loading the graph in memory( provided its not so huge ) would remove the overhead of Data reading and Graph Creating Everythime for every request for a Route.

Go through the Pathgenerators class which Allow you to find a Path based on Constraints.Constrains can be Distance or Customized on Various Parameters based on an interface. I think u will get better idea of this when you look at the API's provided.
This Shoudl Solve your problem.Implementation of Routing Algorithms is also there in geo-tools like Dijkstra's et all ..making your job more simpler.


Am Providing a Sample Code for ur Understanding :
Graph g = lsg.getGraph();  // ge tthe Graph from the Data. or from ur global variable.

MEdgeWeighterImpl mwi = new MEdgeWeighterImpl(); //Cost based Implementaion that u need to refer to from the API depending on your needs ..Someitmes if Trafic data present then even that is to be Consiered ..et all.. 

mwi.setEdgeCostMap(hmEdgeCost);
DijkstraShortestPathFinder dspf = new DijkstraShortestPathFinder(g, srcNode, mwi);
dspf.calculate();
Path p = dspf.getPath(destNode);
if (p != null) {
               return p.getEdges();
                    // actual Rooute Edges .
          } else
                {
               return null;
                    //No Route found Case .
          }




Good Luck Dude ..happy Routing .

Bye.











On Tue, 08 Nov 2005 Jase wrote :
>My current research involves using open source libraries to create an online
>vehicle routing system for taxis or any vehicles as a matter of fact. I have
>done some research and identified Geotools & Geoserver as the best libraries
>for building such a system. After going through the mailing list, it seems
>that the question I am going to ask is quite a common one afterall but there
>is a lack of solution.
>
>I have a PostGIS database of roads in LineStrings. After following the
>tutorials on graphing, I have managed to create the graph network using the
>LineStringGraphGenerator. What I did was to load the entire PostGIS database
>into the linestringgraphgenerator the and the output that I have obtained
>using getGraph() is as follows:-
>
>V = [14042, 3162, 2002, 12968 … ]
>E = [20301 (6097, 20300) … ]
>Is it right to build the entire line network first before traversing even
>though I do not know the points I would like to use?
>
>I understand I should traverse the graph but I am a bit stuck as to how I
>should proceed. Say, if I would like to route from Point A to Point B, how
>would I do that? As a matter of fact, I would like to locate the closest
>vehicle in a particular area and find the quickest route to that point. I
>see that there are many classes that are in the org.geotools.graph package
>but I'm unsure on how to proceed.
>
>I appreciate if anyone can offer an insight to this.
>
>Thanks
>
>Jason