Hi Gregers, Thanks for your reply.
The question was not "how to" yet, but "shall I" ;o) I think I did something similar to the "ends matching" in a python script that creates those polygons (in a particular context that also requires tiling). What I'd like to know, is if there is a reason why it's not already available in gdal, since there is the need for that and apparently algos to reach the goal. > You cannot always make polygons with them unless you are on a perfect island I'm not sure I understand the that. The polygons I have in mind are polygons with holes (multipolygons for a given class actually), is it related to what you're saying ? V. Le 19/10/2017 à 14:23, Hans Gregers Hedegaard Petersen a écrit : > Hi Vincent, > >> I know this is old stuff (references below), but making polygons instead >> of lines would be a great option for gdal_contour IMO. >> >> It could be also another program included in gdal/app (if it is already, >> I can't find it). >> >> What do you think, shall I add that ? If yes, first or second option ? > I had a similar problem years ago, and after making consistent > orientation [1] it is simply a matter of running through the lines and > matching starting points with endpoints in the linestrings. This is a > rather fast operation on a spatially indexed dataset. > > You cannot always make polygons with them unless you are on a perfect > island - for instance I processed Denmark in tiles (over 43000 tiles > of 1x1km) and then "glued" the linestrings together afterwards. Speed > was essential, so I first glued all linestrings in a tile (which would > make a large number of closed linestrings), then between tiles (but > only for those that were not yet closed). > > > Cheers, > > Gregers > > > [1]: https://trac.osgeo.org/gdal/ticket/3129 _______________________________________________ gdal-dev mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/gdal-dev
