achim schrieb: > > achim schrieb: >> Hi, >> >> 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)"? > > to 1) > make sure, the map is connected to the desired database. if necessary > overwrite current connection and delete tables > -> db.droptable -f table=network > -> v.db.connect -d map=netw...@achim > then do a > -> v.db.addtable map=netw...@achim layer=1 > all geometry objects get a number > (maybe a v.category is necessary before) > > -> Questions remaining: > -how can I distinguish between points and polylines? > -how are connections (polyline)-node-(polyline/polyline) stored/defined?
-how can I distinguish between points and polylines? to add a layer you can set a geometry type (eg. type=point) and do a "v.category" (misleading name) in an additional layer v.category --overwrite input=netw...@achim output=netw...@achim type=point layer=2 if you did it wrong before adding all geometries, you can delete (option=del) some of the categories v.category --overwrite input=netw...@achim output=netw...@achim option=del type=line layer=2 (I feel a bit schizo) Questions remaining: -> how are connections (polyline)-node-(polyline/polyline) stored/defined? >> 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, >> Achim >> _______________________________________________ >> 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 _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
