[GRASS-user] Networks

achim ak7 at jupiter.uni-freiburg.de
Thu Jun 4 13:03:35 EDT 2009


I am going to do some work on drainage networks I created. I could not
figure out some basic procedures. Maybe, you have some ideas how to work
with some of the following questions/tasks:

1) how is a network stored? creating it via v.net from a multiline "map"
says it wants to create two layers: one with lines, the other with points
 -> general problem: creating an table containing an entry for every
object (Id). I know thats general, but why doesn't it work with
v.db.newtable? And why answers v.to.db option=cat with
"Reading features... Updating database... 0 categories read from vector
map (layer 1) 0 records updated/inserted (layer 1)"?

2) how can I identify each network by eg. an integer value? There are
many unconnected trees, which I want to keep separated.
 -> I tried it with v.buffer, on the one hand I couldn't upload the
information to the network (points and polylines) and on the other hand
it takes a lot of time.

3) can I define a "direction" of a network with values on the nodes?
like a sorted tree? in order to get the sub trees?

4) how can I find out, which and how many lines are connected to a node?

5) ...there are some, but I think its enough; and furthermore the
questions more or less depend on each other.

Hoping, someone has some experience with that kind of stuff,
kindly regards,

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