Menu
▾
▴
Re: [Geotools-gt2-users] LineString Graph Traversal
|
From: Jase <jas...@gm...> - 2005-11-23 10:43:33
|
hi Justin,
I followed your instructions and am getting errors. Here is what I did.
XYNode src =3D (XYNode)lgb.getNode(new Coordinate (101.603802, 3.071856));
XYNode dest =3D (XYNode)lgb.getNode(new Coordinate(101.71339200,3.15235700)=
);
Error : java.lang.ClassCastException:
org.geotools.graph.structure.basic.BasicNode
at test1.main(test1.java:86)
Line 86 refers to the first line above.
So I thought perhaps I should not have casted it and used this:-
Node src =3D lgb.getNode(new Coordinate (101.603802, 3.071856));
Node dest =3D lgb.getNode(new Coordinate(101.71339200,3.15235700));
and i got the following error:-
java.lang.ClassCastException
at test1$1.getWeight(test1.java:93)
at org.geotools.graph.traverse.standard.DijkstraIterator.cont(
DijkstraIterator.java:184)
at org.geotools.graph.traverse.basic.BasicGraphTraversal.traverse(
BasicGraphTraversal.java:172)
at org.geotools.graph.path.DijkstraShortestPathFinder.calculate(
DijkstraShortestPathFinder.java:85)
at test1.main(test1.java:102)
Line 93 : LineSegment line =3D (LineSegment)e.getObject(); (this is part of
the getWeight method)
Line 102: dsp.calculate();
I did some debugging on dst and src to see if there was a value and there
indeed was...
src=3D27895 while dst=3D6336
Thanks for helping me out with this.....
Jase
On 11/23/05, Justin Deoliveira <jde...@un...> wrote:
>
> Hi Jase,
>
> Looking closer at your code snippet I see the problem. You are creating
> new nodes for src and dest. Instead the nodes need to be pre-existing in
> the graph.
>
> The LineStringGraphGenerator has a method called getNode(Coordinate).
> You can use it to a node in the graph at a particular coordinate.
>
> So instead of:
>
> XYNode src =3D new BasicXYNode();
> src.setCoordinate(new Coordinate (101.603802, 3.071856));
>
> XYNode dest =3D new BasicXYNode();
> dest.setCoordinate(new Coordinate(101.71339200,3.15235700));
>
> You should use:
>
> XYNode src =3D lgb.getNode(new Coordinate(101.603802, 3.071856));
> XYNode dest =3D lgb.getNode(new Coordinate(101.71339200,3.15235700));
>
> Hope that helps, let me know if that works for you.
>
> Justin
>
>
> Jase wrote:
> > hi Justin,
> >
> > I'm not getting any errors. it's just that when i printed the value of
> > "p" i got a null value.
> >
> > Thanks
> >
> > Jase
> >
> > On 11/23/05, * Justin Deoliveira* <jde...@un...
> > <mailto:jde...@un...>> wrote:
> >
> > Hi Jase,
> >
> > Could you send the stack trace of the exception. Thanks.
> >
> > Justin
> >
> > Jase wrote:
> > > Hi Justin,
> > >
> > > Upon closer inspection on my database, I found that the roads
> > have been
> > > noded on the intersections. MOst of the roads I had a look share=
s
> a
> > > common end point.
> > >
> > > I proceeded on with using some of the algorithms that you
> > suggested in
> > > this mailing list. What I'm getting is a null pointer. I'm a bit
> > baffled
> > > as to what might have gone wrong. I initially though that the
> roads
> > > might not have been noded so I tried with two points on the same
> road
> > > and got the same results.
> > >
> > > Attached are the codes that I used. I'm guessing I did something
> > wrong
> > > at the "src" and "dest"
> > >
> > > Thanks.
> > >
> > > Jase
> > >
> > >
> > >
> > > DataStore pgDatastore =3D
> > DataStoreFinder.getDataStore(params);
> > > FeatureSource fsBC =3D pgDatastore.getFeatureSource
> > ("mustmrr");
> > > System.out.println("Road to be added: " +
> > > fsBC.getCount(Query.ALL));
> > > System.out.println("Reading PostGIS datastore...");
> > >
> > > LineStringGraphGenerator lgb =3D new
> > LineStringGraphGenerator();
> > > //FeatureSource fs =3D
> > (FeatureSource)layers.get("mustmrr");
> > > FeatureResults fr =3D fsBC.getFeatures ();
> > > FeatureCollection fc =3D fr.collection();
> > > FeatureIterator feat =3D fc.features();
> > >
> > > Envelope envelope =3D fc.getBounds();
> > > System.out.println ("Building graph network...");
> > > while (feat.hasNext())
> > > {
> > > Feature ft =3D feat.next();
> > >
> > > if (envelope.contains(ft.getBounds ()))
> > > {
> > > System.out.println("Road Name:"+
> > > ft.getAttribute("name").toString().trim() + "\tAtribute:"
> > > +ft.getAttribute("wkb_geometry"));
> > > lgb.add(ft.getAttribute("wkb_geometry"));
> > >
> > > }
> > > }
> > >
> > > Graph g =3D lgb.getGraph();
> > > System.out.println (g);
> > > XYNode src =3D null;
> > > src =3D new BasicXYNode();
> > > src.setCoordinate(new Coordinate (101.603802,
> 3.071856));
> > >
> > > XYNode dest =3D new BasicXYNode();
> > > dest.setCoordinate(new
> > Coordinate(101.71339200,3.15235700));
> > >
> > > DijkstraIterator.EdgeWeighter weighter =3D new
> > > DijkstraIterator.EdgeWeighter()
> > > {
> > > public double getWeight(Edge e)
> > > {
> > > LineSegment line =3D
> (LineSegment)e.getObject();
> > > return(line.getLength());
> > >
> > > }
> > > };
> > >
> > > DijkstraShortestPathFinder dsp =3D new
> > > DijkstraShortestPathFinder(g, src, weighter);
> > > System.out.println("Calculating Paths....");
> > > dsp.calculate();
> > > Path p =3D dsp.getPath(dest);
> > > System.out.println(p);
> >
> >
> > --
> > Justin Deoliveira
> > The Open Planning Project
> > http://topp.openplans.org
> >
> >
>
>
> --
> Justin Deoliveira
> The Open Planning Project
> http://topp.openplans.org
>
|