Dear list, I am curious to find out if it is possible to successfully convert the "boundaries" of a raster map (contains some administrative boundaries) in a vector map.
The problem with this raster map is that the boundaries are represented by non-continuous lines (dots). --- Here is the link to the bad-looking gif files which contain administrative boundaries (prefectures in Greece): http://www.ypes.gr/kapodistrias/greek/kapo/nomoi.htm --- Is there a way to get the biggest portion out of it as vector lines/boundaries and correct manually as less as possible? Thank you, Nikos P.S. My "quick" attempts so far (a) I 've tried using r.zc (edge detection) with no satisfactory results. (b) 1. Save gif from http://www.ypes.gr/kapodistrias/images/i_trik.gif 2. grass -text # and create an xy location 3. r.in.gdal input="/grass_db/kapodistrias/data/i_trik.gif" output="trikala" 4. d.rast trikala cat=3 # cat=3 is the blue color, that is the boundaries of interest. 5. r.mapcalc trikala_3="if(trikala == 3, 3, null())" 6. r.thin input="trikala_3" output="trikala_3.thinned" iterations=200 7. r.to.vect input="trikala_3.thinned" output="trikala_3_thinned" feature="line" 8. v.clean input="trikala_3_thinned" output="trikala_3_thinned_clean" type="line" tool="snap,rmdangle,rmbridge,rmdupl" thresh=16 Probably only snap help here but anyway I tested several options. snap threshold above 20 and below 14 gives few/bad lines. If there is a way to connect the "blue dots" in the raster map then I suppose it would be more or less easy to grab lines from the raster map. _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
