RE: [Cartoweb-users] A question related with using pgdijkstra module

[Fay Du]

Hi Franck:   Hi Franck: Thank you very much. It does help me lot. The node ID is pre-assigned to each town. I have dynamic points, which are from GPS mounted in cars. They must get node ID on the fly. It is why I want some quick method. I wonder except pgdijkstra module, is there any other open source routing program exist? In my application, we must use our own data as clients requirement.   Fay   >Hi Fay, >I think that this is the case for the demo_routing data: the towns (town table) geometry are >independant from the roads (roads_europe  table) ones. >On my side, I tried to replay the procedure given in the manual, section 1.2.4.2. Some steps are not >detailled and I had to search the nearest road start geometry for each town in order to create the >txt field of the roads_europe_vertices table. To get most of the town listed, I had to go up to >2000m, and then get the lowest distance for a given town. >To make it short, the SQL script looks like : >... >CREATE TABLE roads_source_town AS >  select distinct t.txt, source_id, distance(PointN(r.the_geom,1) , t.the_geom) as d from >roads_europe r, town t, roads_europe_vertices >    where t.txt != 'UNK' AND distance(PointN(r.the_geom,1) , t.the_geom) < 2000 AND geom_id = >source_id ORDER BY t.txt , d ; >CREATE TABLE roads_source_town_uniq AS >  select * from roads_source_town a where a.txt IN (select b.txt from roads_source_town b where >a.txt = b.txt  limit 1) AND a.d IN (select b.d from roads_source_town b where a.txt = b.txt  limit >1); >UPDATE roads_europe_vertices set txt = (select distinct txt  from roads_source_town_uniq  where >roads_europe_vertices.geom_id = roads_source_town_uniq.source_id); >... >I am not sure this is the solution done to build the demo_routing.sql database, and it is not >optimized, but it works.   >Also it should be interesting to take in account the whole line geometry of the roads instead of >just the initial point (PointN(r.the_geom,1))...  but this may imply to cut some roads in several >source_id/target_id... >Franck

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