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Hi Johannes: On 04/22/2011 05:15 PM, Johannes Radinger wrote: Am 22.04.2011 um 13:22 schrieb Moritz Lennert:On 22/04/11 11:34, Johannes Radinger wrote:About my situation: I've got a river network, which is a polylinefeature set with 43 lines (43 IDs) included (tree-like shape of a rivernet) all with the same cat-value (1).Now I would like to unite/merge the lines to one feature (1 ID) if that is possible and break that single element at given points with v.edit...Because if I break now at around 40 positions I get over 80 segements (40 old segements and which are broken again at different positions) but there should be only 41 or so... so how can I handle that and assign unique cat values for each segment...(at the moment the don't have to be the same like the breakpoints, just unique values) any suggestions?v.edit tool=catadd id= ?Sorry but I am still confused how to do the break. In the Attachment there is a GRASS-exported shp.-file with my rivernet consisting of 43 single lines. I want to break that river at e.g. 3521021.43671,6041340.79067 which is one point (out of others) along the river. Here's what I tried: GRASS 6.4.0 (WGS84):~/geodata > v.edit river_gen tool=break coords="3521021.43671,6041340.79067" Selecting features... 100% 1 of 43 features selected from vector map <river_gen@PERMANENT> 100% 1 lines broken Building topology for vector map <river_gen>... Registering primitives... 44 primitives registered 17135 vertices registered Building areas... 100% 0 areas built 0 isles built Attaching islands... Attaching centroids... 100% Number of nodes: 45 Number of primitives: 44 Number of points: 0 Number of lines: 44 Number of boundaries: 0 Number of centroids: 0 Number of areas: 0 Number of isles: 0 v.edit complete. So I there are now 44 line segments as opposed to the original 43. One got split into two. But the two new segments have the same cat number. Next I wiped out all the old cats: GRASS 6.4.0 (WGS84):~/geodata > v.category river_gen opt=del cat=1-43 out=river_gen_tmp and recreated new cats into a new vector: GRASS 6.4.0 (WGS84):~/geodata > v.category --o river_gen_tmp opt=add out=river_gen_2 In the attached image you can see that the original line segment with cat=12 (black numbers) got split into two (after the v.edit step). THe red numbers are the new cat values, and that line segment got cats 43 and 44. Reviewing your first post I want to also note: I believe that GRASS's topology model will not allow you to merge the original river segments into one "polyline" (MULTILINE in other GIS). You *can* of course have polylines in GRASS, but they must consist of two line segments connected at exactly one point. In any typical river network you always have three segments intersecting: the upstream reach, the tributary and the downstream reach. Others with more experience may correct me, but I think that if you must merge all the river segments into one "MULTILINE" before splitting at the new points, then you'll have to use some other tool and non-topological vector data format outside of GRASS. Regards, Micha In the end I want two features/categories one on each side of the break. what are the exact steps especially when I want to do it with several points (I know the procedure with a python for loop in combination with v.edit). This mail was received via Mail-SeCure System.Moritz _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-userThis mail was received via Mail-SeCure System._______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user This mail was received via Mail-SeCure System. -- Micha Silver Arava Development Co. +972-52-3665918 http://www.surfaces.co.il |
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