That could well be - it does seem a bit strange that pretty straight roads become so zig zagged - surely also taking up more space in the map itself.
On Sat, 1 May 2021 at 17:23, Gerd Petermann <[email protected]> wrote: > Hi Felix, > > I think one reason for the zig-zagging is that we don't merge roads at > lower resolutions and maybe DouglasPeucker should ignore "preseved" points > at level 1 and higher. > > Gerd > > ________________________________________ > Von: mkgmap-dev <[email protected]> im Auftrag von > Felix Hartmann <[email protected]> > Gesendet: Samstag, 1. Mai 2021 11:17 > An: Development list for mkgmap > Betreff: Re: [mkgmap-dev] Request - set --reduce-point-density= for each > resolution > > haha, no worries. I could have only said, I never noticed that problem. > The main problem is the zig-zagging at lower resolution. > > On Sat, 1 May 2021 at 16:54, Gerd Petermann < > [email protected]<mailto:[email protected]>> > wrote: > Hi all, > > sorry for the noise. Got confused by the special case with > mkgmap:fast_road=yes in the default style. > > Gerd > > ________________________________________ > Von: Gerd Petermann <[email protected]<mailto: > [email protected]>> > Gesendet: Samstag, 1. Mai 2021 10:46 > An: Development list for mkgmap > Betreff: AW: [mkgmap-dev] Request - set --reduce-point-density= for each > resolution > > Hi Felix, > > reg. low resolutions: > I think there is also an error in mkgmap which filters e.g. large parts > (almost all) of motorways at resolution 14. > > Gerd > > ________________________________________ > Von: mkgmap-dev <[email protected]<mailto: > [email protected]>> im Auftrag von Felix Hartmann < > [email protected]<mailto:[email protected]>> > Gesendet: Freitag, 30. April 2021 16:55 > An: Development list for mkgmap > Betreff: Re: [mkgmap-dev] Request - set --reduce-point-density= for each > resolution > > sorry - patch has some typos as i was still playing around with values. > here is a working version. These values I feel are good with 1.3 at > commandline. > > On Fri, 30 Apr 2021 at 22:44, Felix Hartmann <[email protected] > <mailto:[email protected]><mailto:[email protected]<mailto: > [email protected]>>> wrote: > I hardcoded a patch - as I was not sure someone is interested in it. This > is doing the job - but I do feel others could profit as well. And yes I now > understood how I could change this for a map starting at resolution 23 as > well. I'm still not sure why do we not run the DP filter on resolution 24? > I would image a very small value would give some improvement without > visually changing anything. > > I haven't really looked at polygons yet - but my patch looks pretty good > to me if you use a value of 1.3. So just as recommendation for default > values. I feel the current default of 2.6 was exactly that low - because at > resolution 23 a high value is really bad, while at lower resolutions there > is a need for simplification. it's a bad compromise. > > On Fri, 30 Apr 2021 at 20:38, Gerd Petermann < > [email protected]<mailto:[email protected] > ><mailto:[email protected]<mailto: > [email protected]>>> wrote: > Hi Felix, > > you are probably right, the DP filter was not adapted to work with a map > with resolution 23 as highest resolution. A quick change would be to > disable the filter at level 0, similar to a map with max resolution 24. > The --reduce-point-density sets the error distance for the Douglas-Peucker > (DP) algorithm. > If I got you right that's not enough for a map with levels = 0:24, 1:23, > ... because you would want to use a rather small error distance for the > first two layers and a higher value for the rest. Sounds reasonable to me. > Probably also for --reduce-point-density-polygon. > > I'll try to implement both. > > Gerd > > ________________________________________ > Von: mkgmap-dev <[email protected]<mailto: > [email protected]><mailto: > [email protected]<mailto: > [email protected]>>> im Auftrag von Felix Hartmann < > [email protected]<mailto:[email protected]><mailto: > [email protected]<mailto:[email protected]>>> > Gesendet: Mittwoch, 28. April 2021 05:03 > An: Development list for mkgmap > Betreff: [mkgmap-dev] Request - set --reduce-point-density= for each > resolution > > As I'm not sure everyone is following the other topic, I would like to ask > to introduce the possibility to set different values for the DP filter > based on resolution. > > Why is this important? > > a) maps which are produced with resolution 23 as highest resolution need > to have a much lower level than subsequent resolutions. > b) For resolution 23 and 22 a lower level makes sense - it is not needed > as much here to speed up the gps device map drawing speed, while for lower > resolutions like 18-21 a high level is really needed else map panning > becomes painfully slow (usually basemap kicks in at 17). > > If I'm correct right now 2.6 at resolution 23 would be 5.4 at resolution > 22, 10.8 at resolution 21 and so on. It's okay to keep that behaviour - but > the value doubled just needs to be possible to be set for each resolution. > It doesn't matter to me if we keep it like that or if we change the numbers > than ourselves by resolution. Important thing is that it's possible to be > set for each resolution > > c) maybe also introduce the possibility to set DP for resolution 24. I > think a value of 0.3-0.6 could be worth it. I'm not sure if there were some > problems preventing DP to be used at 24. However as by now I think mkgmap > is able to produce routable maps starting at 23 instead of 24, those > problems should be fixed... > In general I think a map made for automotive use (car, motorcycle) would > be fine using resolution 23 as a start instead of 24. Like Garmin City > Navigator maps do. But then yes it's really important to not have a high DP > value on resolution 23. Same as contourlines only maps which make sense at > resolution 23 instead of 24. > > -- > Felix Hartman - Openmtbmap.org & VeloMap.org > > _______________________________________________ > mkgmap-dev mailing list > [email protected]<mailto:[email protected] > ><mailto:[email protected]<mailto: > [email protected]>> > https://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev > > > -- > Felix Hartman - Openmtbmap.org & VeloMap.org > > > > -- > Felix Hartman - Openmtbmap.org & VeloMap.org > > _______________________________________________ > mkgmap-dev mailing list > [email protected]<mailto:[email protected]> > https://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev > > > -- > Felix Hartman - Openmtbmap.org & VeloMap.org > > _______________________________________________ > mkgmap-dev mailing list > [email protected] > https://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev > -- Felix Hartman - Openmtbmap.org & VeloMap.org
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