On 02/14/2013 10:10 AM, David J. Bakeman wrote: > On 02/14/2013 08:58 AM, magerlin wrote: >> Hi - I've tried the one building a time approach but have not been able to >> get through. >> It is very kind of you Victor to offer to have a look at it and perhaps >> include it in your blog. > Perhaps you could use the extract nodes routine to extract the points > from each building and include those along with the points inside the > building polygons? That way even if there are no points inside a > building there would still be at least 3 points? Ofcourse the ftools > extract nodes does not appear to handle selected polygons either but you > could do that in grass with v.extract type=point. Another idea might be > to use a Delaunay triangulation of the points in a building with the > addresses in a building using v.delaunay. OK the delaunay was a bad idea I don't know what I was thinking :-[ Anyway I still think it might be useful to include the points from the building polygon so you always have enough points. >> You can get my data and model files here: Get data >> <https://dl.dropbox.com/u/8189384/Break%20Polygons%20by%20Points.zip> >> The zip file includes both some test data (looking almost like the picture >> in my first post) but also some nasty real data with about 14.000 buildings! >> Also two model files are included: The one used to create the picture in my >> first post and my attempt to the iterative procedure. >> >> Executing the "Break Polygons by Points iteratively.model" give me an error >> message: >> >> <http://osgeo-org.1560.n6.nabble.com/file/n5034373/Error_msg.png> . >> There are no messages in the log. >> >> My general experiences so far has been: >> * I need to use the Grass v.voronoi since the Qgis "Voronoi polygons" uses >> the whole layer even if selections exist >> * v.voronoi stops with an error message if less than 3 points in the >> building but it has problems handling situations also with bigger (but >> small) numbers. In the example below with 5 points it has only made 3 >> voronoi polygons: >> <http://osgeo-org.1560.n6.nabble.com/file/n5034373/5_points_not_ok.png> >> Some other situations with 5 points are handled correctly! >> * Due to the above mentioned limitations and since I need to be able to also >> split buildings with only 2 points I have experienced that the addition of >> some temporary additional points at the (far) edge of the Analysis Extent >> will help when they are included in the creation of Veronoi polygons for >> every building >> * With the large number of polygons in my real data I think the iterative >> process at each step should append the new Voronoi polygons inside the >> building to a "collecting" layer of split buildings (at the end beeing the >> result layer) - otherwise the algorithm must at the end be able to merge an >> unknown big number of shape files. >> >> >> My experiences with Sextante: It is marvellous to now be able to make your >> own routines and it is quite simple with the modeler! I have no knowledge of >> python so I have not come to the scripts yet. >> >> I have an undocumented feeling that Sextante in the background "saves" some >> setting and sometimes unintentionally (at least from my point of view ;-) >> keeps them for later runs of other geoalgorithms? >> Sometimes it could seem to be due to (not reported) problems with >> overwriting existing files. I have experienced several times that my >> "Break_Polygons_by_Points.model" stops to function (nothing happens when >> running it) but closing down Qgis and restarting makes it OK again. It could >> perhaps also be some saved analysis extents? >> >> >> >> >> >> >> >> ----- >> Regards Morten >> >> Qgis 1.8.0 Stand alone installer in Win7 64 bit >> -- >> View this message in context: >> http://osgeo-org.1560.n6.nabble.com/Any-ideas-Splitting-polygons-to-only-have-one-point-in-each-polygon-tp5034081p5034373.html >> Sent from the Quantum GIS - User mailing list archive at Nabble.com. >> _______________________________________________ >> Qgis-user mailing list >> [email protected] >> http://lists.osgeo.org/mailman/listinfo/qgis-user >> > _______________________________________________ > Qgis-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/qgis-user >
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