Hi Mike, some answers: - the unit is metre, it is scaled with this formular: maxErrorDistance = filterDistance * (1<< (24 - resolution)), so factor 4 for resolution 22, 8 for 21, 16 for 20 and so on. - The default is 2.6 if the option is not given or given without a value. The --no prefix doesn't work, but the Douglas-Peucker filter can be switched off with a value of 0. - I used different option names because I think --reduce-point-density is a bit misleading. I didn't think about changing the syntax of the existing option, but it would be an alternative. - Why different option for polygons? See http://gis.19327.n8.nabble.com/Include-the-following-patches-into-trunk-Patch3-quot-reduce-point-density-polygon-quot-tc5327721.html
I really have no clue how one (Felix) determines his favorite values and it's not interesting for me as a software developer. @Steve Reg. online doc: I don't know if this is intended. I'd prefer to have separate docs for each branch, or that branch builds don't change the web page, whatever is easier. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-boun...@lists.mkgmap.org.uk> im Auftrag von Mike Baggaley <m...@tvage.co.uk> Gesendet: Montag, 14. Juni 2021 22:32 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] Documentation for the new Douglas-Peucker options in low-res-opt branch Hi Gerd, I think the original documentation for --reduce-point-density and --reduce-point-density-polygon could do with some improvement. It also seems bizarre to have a recommended value that is not the default. Is 2.6 the default if --reduce-point-density is specified without a value, or is it also the default if the option is not specified? Are the units metres? Is the distance the same no matter what resolution is used, or does the distance increase at lower resolution? If the former, wouldn't it be better to increase by a factor of 1.414 at successive resolutions? Would this be sufficient to not need to be able to specify individual values for resolutions? I'm not keen on having two very differently named options that basically achieve the same aim and suggest that it would be better to simply extend the existing --reduce-point-density options with --reduce-point-density=value|resolution:value[,...] or even better --reduce-point-density=value[,...] where the first value applies to the first used resolution and so on, with the last value being scaled for any further resolutions that have not had a value specified. Is there a reason why polygons need different values than lines? Shouldn't reduce-point-density-polygon default to the reduce-point-density value? I note that although the documentation belongs to the low-res-branch, it is showing up on the mkgmap command line web page. Regards, Mike -----Original Message----- From: Gerd Petermann [mailto:gpetermann_muenc...@hotmail.com] Sent: 14 June 2021 07:43 To: mkgmap-dev@lists.mkgmap.org.uk Subject: [mkgmap-dev] Documentation for the new Douglas-Peucker options in low-res-opt branch Hi all, I've now added documentation for these new options, see: https://www.mkgmap.org.uk/websvn/diff.php?repname=mkgmap&path=%2Fbranches%2F low-res-opt%2Fresources%2Fhelp%2Fen%2Foptions&rev=4775&peg=4775 Is it clear enough? I think the recommend value --reduce-point-density-polygon=8 is far too high at low resolutions. Should this be changed? Together with the new --improve-overview option this branch version can produce much better results for the lower resolutions. Gerd _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk https://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk https://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
