Jim, please post your GRASS version to the list to better help.
Markus On Thu, Aug 28, 2014 at 1:40 PM, James Keener <[email protected]> wrote: > I'm trying to create a map with isolines for the road-distance places > are from bus routes. I was trying to roughly follow > http://jcastellssala.wordpress.com/2012/05/07/basic-network-analysis-with-grass/ > but I don't quite get similar results (I feel like the network isn't > completely connected, but this is the first time I'm doing this so it's > more likely I'm just doing it wrong. > > I am using the following shapefiles in SRID 2272 (NAD83 / Pennsylvania > South (ftUS)): > > http://jimkeener.com/grass-topo-question/roads.tar.bz2 which is the > TIGER road graph for Allegheny County, PA, USA (state fips = 42, county > fips = 003), but reprojected to 2272 and a "length" attribute added. > > http://jimkeener.com/grass-topo-question/stops.tar.bz2 which is derived > from the Port Authority of Allegheny County GTFS file found at > http://www.portauthority.org/paac/CompanyInfoProjects/DeveloperResources.aspx > and reprojected to 2272. > > > So, the first thing I did is import these files: > >> v.in.ogr dsn=roads.shp layer=roads output=roads >> v.in.ogr dsn=stops.shp layer=stops output=stops > > (http://jimkeener.com/grass-topo-question/ac.png) > > Then I connect the stops to the network > >> v.net input=roads points=stops output=network operation=connect thresh=500 > > Connect the require database layer > >> v.db.connect map=network table=schools layer=2 > > Then allocate the network > >> v.net.alloc --overwrite --verbose input=network output=network_alloc >> ccats=1-6965 > > (http://jimkeener.com/grass-topo-question/ac-alloc-zoom-thumb.png when > displayed with d.vect -c) (the little Xs are bus stops > > And create isolines at 1-, 2-, and 3- thousand feet > >> v.net.iso --overwrite input=network output=network_isolines ccats=1-6965 >> costs=1000,2000,3000 afcolumn=LENGTH abcolumn=LENGTH > > (http://jimkeener.com/grass-topo-question/ac-isolines-zoom.png also with > d.vect -c) > > All but a few of the roadways near the open space to the right (a park > and very hilly (even by Pittsburgh standards:-p) area) are within 3000 > feet of a bus stop. Therefor I was expecting almost all of the roads to > be highlighted in different colors representing their distance from a stop. > > Thank you for any help! > Jim > > > _______________________________________________ > 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
