On Tue, Mar 11, 2014 at 4:09 PM, Patrick S. <[email protected]> wrote: > Dear list, > > I hope you can help me to understand the behavior of GRASS for the > following: I need calculate the network-distances for intersections in this > network. What seemed easy, starts to get very tricky.... > > My approach is shown below, but has following problems: > > 1.) As intersections need to be dedicated with a category, I extraced the > intersection-points with v.net so that I can connect them to their network. > (is this really needed?) The following execution of the command > v.net.allpairs generated errors: I think this might be due to missing > categories for the new points? But adding a table, connecting it to the > layer and filling in categories resulted in errors concerning already > existing attribute tables. Can GRASS handle several layers for one map in > PostgreSQL at all? > > 2.) Exporting and reimporting is a bit hacky, but solves issue 1. After > connecting this new pointlayer to the network, I get a map consisting of > points and lines in the same layer, as expected by v.net.allpairs. However, > I have the feeling that the categories are not distinct, so I have a point > and a line with the same cat-values. I expect this to have an effect on > v.net.allpairs? The command v.net.allpairs does run (with the code below), > but the output is not at all clear: I get the expected number of objects in > the table (square of number of points), but the categories start with "1", > which is not even existing in my original network. So what will cat "1" > stand for than and how can I get v.net.allpairs to use the category of the > points in the output? > > My code runs on GRASS 6.4.3 from Ubuntu-Repos with PostgreSQL 9.1. as > database.
v.net.allpairs does not work properly in GRASS 6. You need to use GRASS 7 if you want to use this module. Markus M > > #___network cleaning and extracting intersections connecting to new network > v.build.polylines in=net_clean out=net_segm cats=first --overwrite > v.net in=net_segm out=intersections op=nodes --o > v.out.ogr in=network dsn="network.shp" type=point #re-import to create > pt_layer with category > v.in.ogr dsn="network.shp" out=network_pt type=point > v.net gr_streets_clean points=network_pt op=connect thresh=200 out=network > nlayer=1 --o > > #___ create o-d-table with costs > v.net.allpairs in=network out=streets_shortpath_od af=cost_speed > ab=cost_speed -a --overwrite > > I'd appreciate any hint! > > Patrick > > > Patrick Schirmer, > Institute for Transport Planning and Systems > ETH Zürich > > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
