On Wed, 30 Jan 2019 at 19:52, Christoph Dohm <cd...@gmx.de> wrote: > > Hi, > > I'm trying to work on a routing problem for my Python plugin and I wanted to > use the Dijksta algorithm for that. I used QGIS 3.0 Girona first, but > upgraded to 3.4 Madeira recently but getting the same result. > > I tried to work along the Code from the Cookbook and also used the book > "Building Mapping Applications with QGIS" from Erik Westra, which is > basically the same Code as in the Cookbook. > > Since those sources are from QGIS 2 I had to make some adaptions (import from > qgis.analysis library instead qgis.networkanalysis and some others) My Code > seems to be working now, but the results aren't usful as it no matter what I > do only gives me a -1 for every vertex in the tree. > > I posted my problem on stackexchange with the Code that I'm using. > > https://gis.stackexchange.com/questions/308244/dijkstra-finding-shortest-path-gives-back-a-tree-with-only-1-in-it > > I'm a little lost. I don't understand why it is not working.
There was a bug fixed recently which mostly impacted network routing when geographic coordinate systems were used. Could this apply to you? Nyall > > Sincerely > > Chris > > > > > Here is a part of the Code I'm using > > > director = QgsVectorLayerDirector(layer, -1, '', '', '', 3) > > strategy = QgsNetworkDistanceStrategy() > > director.addStrategy(strategy) > > builder = QgsGraphBuilder(crs) #crs = project.crs() which is in this case > WGS84 > > tiedPoints = director.makeGraph(builder, [startPt, endPt]) > graph = builder.graph() > > startVertex = graph.findVertex(startPt) > > (tree, cost) = QgsGraphAnalyzer.dijkstra(graph, startVertex,0) > > > > > _______________________________________________ > QGIS-Developer mailing list > QGIS-Developer@lists.osgeo.org > List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer _______________________________________________ QGIS-Developer mailing list QGIS-Developer@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
