Shortest path around polygons
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Shortest path around polygons
by tommy408
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I'm really new to PostGIS. I need to solve this problem. Find the shortest path around polygons from point A to point B.
Here is a better description: http://alienryderflex.com/shortest_path/ How can I do it with PostGIS. Or if you can give me some hints to narrow my search. Thank you. |
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Re: Shortest path around polygons
by Suhr, Ralf
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Solving your problem is not realy hard but time expensive.
- install pgRouting - create one table for the polygons - create one table for holding linestrings - write a function that: - build all possible lines in one polygon (makeline from cross join points from polygon) - remove lines wich are outside the polygon - write lines with extra attribute polygon_id in the linestring table - run add_vertices (pgRouting function) - create temporary table for your "two points" (linestring geometry) - rerun the function for creating linstrings with the two points and all polygon points - finaly run shortest_path( join two tables ) -----Ursprüngliche Nachricht----- Von: postgis-users-bounces@... [mailto:postgis-users-bounces@...] Im Auftrag von tommy408 Gesendet: Donnerstag, 25. Juni 2009 15:35 An: postgis-users@... Betreff: [postgis-users] Shortest path around polygons I'm really new to PostGIS. I need to solve this problem. Find the shortest path around polygons from point A to point B. Here is a better description: http://alienryderflex.com/shortest_path/ How can I do it with PostGIS. Or if you can give me some hints to narrow my search. Thank you. -- View this message in context: http://www.nabble.com/Shortest-path-around-polygons-tp24203378p24203378.html Sent from the PostGIS - User mailing list archive at Nabble.com. _______________________________________________ postgis-users mailing list postgis-users@... http://postgis.refractions.net/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list postgis-users@... http://postgis.refractions.net/mailman/listinfo/postgis-users |
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Re: Shortest path around polygons
by tommy408
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Thank you for your help.
If my polygon table is huge, it would have to consider all the polygon in space? Is there a way I can narrow down only polygons are that in the way between point A and B?
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Re: Shortest path around polygons
by Daniel Kastl-2
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Hi,
First I agree with Ralf and would also use pgRouting for this. I think you have a network table and a polygon table, right? When you search for the shortest path from A to B with pgRouting, you usually won't load the complete data but a bounding box area that includes A and B. You could then further exclude network links that are within your polygons and search the shortest path through your "reduced" network. Daniel tommy408 schrieb: > Thank you for your help. > If my polygon table is huge, it would have to consider all the polygon in > space? Is there a way I can narrow down only polygons are that in the way > between point A and B? > > > > Suhr, Ralf wrote: > >> Solving your problem is not realy hard but time expensive. >> - install pgRouting >> - create one table for the polygons >> - create one table for holding linestrings >> - write a function that: >> - build all possible lines in one polygon (makeline from cross join >> points from polygon) >> - remove lines wich are outside the polygon >> - write lines with extra attribute polygon_id in the linestring table >> - run add_vertices (pgRouting function) >> - create temporary table for your "two points" (linestring geometry) >> - rerun the function for creating linstrings with the two points and all >> polygon points >> - finaly run shortest_path( join two tables ) >> >> >> -----Ursprüngliche Nachricht----- >> Von: postgis-users-bounces@... >> [mailto:postgis-users-bounces@...] Im Auftrag von >> tommy408 >> Gesendet: Donnerstag, 25. Juni 2009 15:35 >> An: postgis-users@... >> Betreff: [postgis-users] Shortest path around polygons >> >> >> >> I'm really new to PostGIS. I need to solve this problem. Find the >> shortest path around polygons from point A to point B. >> >> Here is a better description: http://alienryderflex.com/shortest_path/ >> >> How can I do it with PostGIS. Or if you can give me some hints to narrow >> my search. >> >> Thank you. >> -- >> View this message in context: >> http://www.nabble.com/Shortest-path-around-polygons-tp24203378p24203378.html >> Sent from the PostGIS - User mailing list archive at Nabble.com. >> >> _______________________________________________ >> postgis-users mailing list postgis-users@... >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> _______________________________________________ >> postgis-users mailing list >> postgis-users@... >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> >> > > _______________________________________________ postgis-users mailing list postgis-users@... http://postgis.refractions.net/mailman/listinfo/postgis-users |
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