On Wed, Mar 30, 2011 at 11:14 PM, Richard Chirgwin <[email protected] > wrote:
> On 30/03/11 9:21 PM, [email protected] wrote: > >> Hi all, >> >> I'm trying to use v.delaunay to get the lines connecting centroids in >> thiessen polygons because I need to compute some statistics on the length >> of >> those segments. >> I'm facing a problem that maybe somebody could help me to solve. >> >> Basically I run v.delaunay with the -l option to get lines instead of the >> polygons, I get the resulting vector, but there is no attribute tables >> associated to it. >> My idea was to run v.db.addtable to create a new empty attribute table, >> then >> v.category to assign cat numbers and the v.to.db to compute and add to the >> attribute table the parameter I need (ie the length). >> The problem is that when I run v.category nothing happens, and the >> attribute >> table remains empty. >> >> Am I missing somethng? >> >> Any help appreciated. >> >> Ing. Andrea Pogliaghi >> Milano - Italy >> > Thoughts ... > > Hi Richard, > 1. Try skipping the v.category step. Try v.to.db option=cat column=cat > I did, but it still doesn't work.... When I run v.to.db I get: GRASS 6.4.0 (utm32):~ > v.to.db map=a_lidar_delaunay option=cat column=cat Reading features... 100% Updating database... 100% 0 categories read from vector map (layer 1) 0 records updated/inserted (layer 1) and the attribute table is still empty. > > 2. What do you get from v.info on the v.delaunay output? > That's the output: v.info a_lidar_delaunay +----------------------------------------------------------------------------+ | Layer: a_lidar_delaunay | | Mapset: andre | | Location: utm32 | | Database: /home/andrea/grassdata | | Title: | | Map scale: 1:1 | | Map format: native | | Name of creator: andrea | | Organization: | | Source date: Thu Mar 31 09:07:59 2011 | |----------------------------------------------------------------------------| | Type of Map: vector (level: 2) | | | | Number of points: 0 Number of areas: 0 | | Number of lines: 29971 Number of islands: 0 | | Number of boundaries: 0 Number of faces: 0 | | Number of centroids: 0 Number of kernels: 0 | | | | Map is 3D: No | | Number of dblinks: 1 | | | | Projection: Universal Transverse Mercator (zone 0) | | N: 5150078.68 S: 5150000 | | E: 1738099.33 W: 1738000.01 | | | | Digitization threshold: 0 | | Comments: | | | +----------------------------------------------------------------------------+ If I run v.delaunay without the -l switch (and thus not obtaining the lines but the whole triangles), then v.category and v.to.db work,so I think that maybe there's some issue with the way v.delaunay generates the lines? Cheers Andrea > Cheers, > Richard > >
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