New answers tagged network
pgr_createTopology does not "fix" disconnected graphs if two endpoints are not within a certain tolerance. SELECT pgr_createTopology('edge_table',0.001); 0.001 in this example is the snapping tolerance and it's unit (meter or degree) is the same as the unit of your data. pgr_createTopology never splits linestrings. It assumes, that there is no ...
I ended up using this workflow in Arc.: Buffer road lines by a trivial distance (e.g. 1 Foot) Select the “Dissolve All” options in Arc to merge all overlapping road buffers. Convert multi-part to single part. Convert feature to line. Collapse dual lines to center lines.
You are looking for what is called the "strongly connected components" in graph theory jargon. These network islands can be computed in QGIS with the grass plugin - See v.net.components.
To revert line direction you can go with v.edit and the flip option.
Ok,so I think I found an answer to my problem. Basically, hierarchy is used in long-distance networks where a lot of routes must be solved. Say if you are traveling from Vancouver to Seattle, hierarchy will help you solve the route faster. Instead of solving for all small routes, the solver will solve based on hierarchy and excludes smaller roads until it ...
There should be no problem using PgRouting for this purpos, and it should be pretty straight forward to prepare your data as routable network. I build a network similar to yours based on transtools data for Europe, and it was working within an hour. Load the data into the database in whatever way you have them, and they can be prepared with SQL - use this ...
Ok, I tried everything again. I am working in a database so I created separate feature classes and removed all costs but length ( you need to at least have one to run the network ) yet ,it is not working. So I even made the network much simpler, I can't humanly make it simpler than this. Attached are the pictures: Note: the red line hierarchy :1 The green ...
Have you followed the guidelines on these pages? http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//004700000057000000 http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//004700000020000000 "Using hierarchy by default As long as the network dataset has a hierarchy attribute, you can set any network analysis layer you create to use ...
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