On Wed, Oct 5, 2016 at 3:05 AM, Sam Snellings <[email protected]> wrote: > Markus, > > Thank you for the suggestions. I ran the following commands nine times on > the data, with thresholds .00000000000000000001, 0.0000000001, 0.0000001, > 0.00001, 0.01, 0.1, 1, 10, and 100. Let me know if I'm not going small > enough. > > v.clean --overwrite input=roads output=roads_snap -c tool=snap thresh=[see > above] > v.net --overwrite input=roads_snap points=schools output=network > operation=connect thresh=1000 > v.net.alloc --overwrite input=network output=network_allocation ccats=1-2 > > I did not get a complete allocation of road segments from any of them, and > as far as I can tell it got stuck at the same vertices on each run. > > I will email you a link to the data off-list, thanks for taking a look.
thanks for providing a link to the data! The problem is that the roads are 3D with z coordinates not matching at the end of a road segment and the beginning of another road segment. The solution is to import roads as a 2D vector with v.in.ogr -2. 2D snapping with v.clean tool=snap thresh =1 might be helpful. Markus M > > -Sam > > On Tue, Oct 4, 2016 at 3:53 PM, Markus Metz <[email protected]> > wrote: >> >> On Tue, Oct 4, 2016 at 5:09 PM, Sam Snellings <[email protected]> >> wrote: >> > I've been running some trials through v.net.alloc using town road >> > networks >> > as the arc layer and schools as the node layer. I have one set of >> > roads/schools that breezes through v.net.alloc without issue (Town 1), >> > while >> > another one only allocates the first few arcs connected to each school >> > and >> > leaves the rest of the network unallocated (Town 2). There is probably a >> > problem with the data from Town 2, but I can't figure out what it is. >> > Does >> > this issue sound familiar to anyone? >> > >> > I am using the GUI. I load each pair of shapefiles into GRASS and then >> > run >> > the following statements (I only import two school points to simplify). >> > The >> > two towns are pulled right from the state-wide GIS office, but the towns >> > are >> > in different states (ie - different agencies provide the data). >> > >> You do not need this for v.net.alloc: >> > v.net input=roads output=road_nodes operation=nodes >> it will create a point for every node, the first point will have >> cat=1, the second cat=2 which collides with the points you want to >> attach >> >> > v.net input=road_nodes points=schools output=network operation=connect >> > thresh=1000 >> >> rather use >> v.net input=roads points=schools output=network operation=connect >> thresh=1000 >> >> > v.net.alloc input=network output=network_allocation ccats=1-2 >> >> the real problem is probably a data problem: roads are not properly >> connected, i.e. the end of one road does not match the beginning of >> another road. Try v.clean input=roads output=roads_snap -c tool=snap >> with a very small threshold. This kind of error is quite common with >> shapefiles (not a fault of the shapefile format but of the software >> used to create the shapefiles). >> >> > >> > Thanks in advance for any advice, I can also email images/data if that >> > would >> > be helpful. >> >> If v.clean -c tool=snap does not help, (links to) original data of the >> schools and road network for Town 2 would be helpful (data please only >> off-list). >> >> Markus M > > > > _______________________________________________ > 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
