On 02/09/2012 11:59 PM, sluedtke wrote:
Dear friends, I have been trying for some hours now but could not find any solution.We do have a shape file of a river network, but a bad one because single rivers consist of multiple lines. Just think of the easiest example, a river with one tributary. I would like to end up with an vector dataset that holds 2 lines for this example, one for the river and one for the tributary of course. In my case, the dataset holds, just as an example, 10 lines, and a distinct set of them makes either the river or the tributary. The lines of each set are connected by the nodes of the single lines. Any ideas how to get ride of this format are very welcome. You might be interested in this thread from a year ago. http://osgeo-org.1560.n6.nabble.com/snap-point-to-line-break-line-at-given-points-tp3887413p3887413.html The short story is that GRASS builds topology when importing a line vector. So each intersection of two lines (i.e. a tributary that branches off the main channel) will be made into a separate line. You can force GRASS to ignore topology, but you probably don't want to. And a correct river network does indeed keep each stream reach as a separate line. (Then you can use the various river network modules r.stream.*). So maybe your original shapefile is not "bad"... What you can do it add an additional column to the vector attrib table and indicate, in that column, which tributary each segment belongs to. THen you can select, display, label, calculate, etc based on this "tributary" attribute column. Would that help? Thanks in advance, Stefan -- View this message in context: http://osgeo-org.1560.n6.nabble.com/How-to-link-or-combine-adjacent-vector-lines-tp4381557p4381557.html Sent from the Grass - Users mailing list archive at Nabble.com. _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user This mail was received via Mail-SeCure System.
-- Micha Silver GIS Consultant, Arava Development Co. http://www.surfaces.co.il |
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