Forum #23 - Topic #150 - Message List
Hi,
I've a Problem with the routing result and I guess it depends on the precision I’m using with the assign_vertex_id().
I'm working with the data of bavaria from http://download.geofabrik.de/osm/europe/germany/ in the WGS84 (srid 4326).
I used different values for the precision:
0.001 (http://pgrouting.postlbs.org/wiki/Workshop-PrepareDikstra): There is a result, but there a many paths which are not connected to each other
0.0001 (http://pgrouting.postlbs.org/discussion/23/36): Depending on the start and end point there is a result file with or an empty route in the xml file. But if there is a result, it is obvious not the shortest path. Although little streets are in my database, he seems to prefer main roads.
5 (http://www.selbstverwaltung-bundesweit.de/mapserver/routinganleitung.zip): The result xml contains an empty route.
Thanks for any help. If necessary I am able to publish different version. Also I am available under skype or icq.
Greets EnochRoot?
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Message #510
The "precision" parameter (you can also call it a "snapping" tolerance) defines from which distance between two nodes the node is seen as one node and connects two (or more) road links.
The dimension of this parameter is the same as that of your projection. It can be "meter" for example, in your case it is degree (WGS84).
If your data quality is very good, you don't really need to care about this parameter and keep it very small. In case of OSM road network data is often not connected well. The snapping parameter can help you to eliminate some errors, but it won't solve everything. I don't think there is another way than playing around with different values and then choose the one that works best for you.
daniel06/10/08 23:59:58
