[mkgmap-dev] Sensible resolutions - (or patch 5)From Felix Hartmann extremecarver at gmail.com on Sat Mar 26 12:56:18 GMT 2011
On 26.03.2011 13:11, Charlie Ferrero wrote: > On 26/03/2011 15:50, Johann Gail wrote: >> Actually, we do have a mean: if there are multiple parallel tracks (each >>> drawn as a separate way with railway=*), it is a major railway. It >>> should be doable to merge adjacent ways at lower resolutions and sum the >>> "weights" of the ways, to decide what to draw. A style file extension >>> could be useful, to specify e.g., the following: >>> >>> * draw individual railways at resolution 24 >>> * merge parallel tracks to one and draw them at resolution 22..23 >>> * merge parallel tracks to one and draw if count>1 at resolution 21 >>> * merge parallel tracks to one and draw if count>3 at resolution 20 >>> >>> For polygons, it could be useful to specify the minimum size that >>> qualifies for inclusion in a given resolution. Of course, small adjacent >>> polygons would have to be merged together first. >>> >>> I am beginning to think that it could be useful to have low-resolution >>> versions of the OpenStreetMap data, generated by an experimental >>> algorithm that attempts to merge polygons and lines as suggested above. >>> If it is not too CPU intensive to merge adjacent areas and lines, >>> perhaps it could be implemented inside mkgmap after all. >>> >> I'm thinking since some time about an algorithm for merging small >> polygons. Up to now I have not found an suitable algorithm. In another >> case I have thought about merging parallel lines, especially the both >> tracks of highways. >> While reading your mail I got the insight, that this are possibly two >> similar problems. In both cases there should be two objects with a small >> space between it be replaced by a merged single one. >> >> The algorithm in general would be: >> - Increase all polygons/lines with a outline. >> - Check all increased polygons, if some of them overlap. >> - If so, merge the original version of them. >> >> But I expect this to be a really resource hungry task. >> >> Regards, >> Johann. >> > I thought the --merge-lines option did part of what you're saying? i.e. > merge lines at low zoom levels. If it doesn't do that, then what does > --merge-lines do? > > it merges a single street consisting of several parts (behind not beside each other) into one street if name is equal (more or less).
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