See below. Michael Barton School of Human Evolution &Social Change Center for Social Dynamics & Complexity Arizona State University
...Sent from my iPad On Oct 6, 2012, at 1:52 PM, "Moritz Lennert" <[email protected]> wrote: > On 06/10/12 03:35, Michael Barton wrote: >> 2. The lack of ability to query a network vector is a bug I think. >> I'm guessing it's in v.what, but am not sure. Can you test to see if >> you cannot query it either? > > I'll test when I get back to the office on Monday, but as a network vector is > not different in essence from any other vector, either you can reproduce this > querying issue with all vectors, or I would need much more precise info about > what you are doing and what exactly is not working. I did this and filed a bug report. > >> 3. v.net.path works fine with your example, but I still don't know >> what the format should be when using cat values. Why 2 integers >> before the cat value? > > As the man page indicates, you have the choice of two formats to feed the > module the info about the path you want. > > 1) When you want to use nodes with cat values as start and end point, just > indicate the cat of each. > > id start_cat end_cat > > 2) When you want to use coordinates as start and end point, you indicate x,y > of start then x,y of end > > id start_x start_y end_x end_y > > The 'id' is an arbitrary cat value that you attribute to the resulting path. > > Each line represents one path going from its start to its end through the > network. Thanks. I don't know why this was not working. But it is now. > >> 4. I'm still not sure of the proper workflow to create a network from >> an existing vector of lines--like a road or stream network--assuming >> that I'm happy to use nodes at intersections in the original vector >> map as network nodes. > > If you just want to use the intersections of the network, then v.net > operation=nodes is what you need. > If you want to connect points to a network (example: points representing > schools to the network of streets) then you have to use operation=connect. > > The reasoning behind the second is that network analysis needs a > topologically clean network, meaning that if you want to find the path form > one node to another, these nodes have to be connected to the network for this > to work. operation=connect does exactly that. If display your network after > connection with nodes, displaying both the network on layer 1 and the nodes > on layer 2, and you zoom very close to one of the nodes you connected, you > will see that there is now a short line segment connecting the node to the > nearest line of the network. This is a BIG help for this key module. NOW I understand how it is supposed to work. Michael > > > Moritz _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
