[mkgmap-dev] Commit r4703: improve RoadMerger (based on merge-roads-reversed-v6.patch)

Wed May 12 15:58:30 BST 2021

Ah true, if the dp filter changes differently it would not be good. I think
the key could include the max level for no direction change. Just on add
the smaller resolution would need to be considered. However with level 0 dp
filter being invisible in changes anyhow, it's really only important for
level 1 or higher if direction for continue ways can be merged or not.

Also oneway street could be reversed at level 1 or higher.

On Wed, 12 May 2021, 22:37 Gerd Petermann <gpetermann_muenchen at hotmail.com>
wrote:

> Hi Felix,
>
> I don't understand why you think that the direction is only important at
> level 0. Doesn't that depend on the TYP file and the style?
> Still, you are probably right that mkgmap could ignore the direction if
> that doesn't produce visible differences. We just have to find out if there
> is a fixed limit or if we need more options or special tags.
> What I try to avoid is the situation that the road is merged and therefore
> possibly reduced to a straight line while overlay lines are not merged and
> possibly zig-zagging along the road.
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von
> Felix Hartmann <extremecarver at gmail.com>
> Gesendet: Mittwoch, 12. Mai 2021 15:08
> An: Development list for mkgmap
> Betreff: Re: [mkgmap-dev] Commit r4703: improve RoadMerger (based on
> merge-roads-reversed-v6.patch)
>
> Actually besides rivers all lines can be reversed from level1 onwards - Is
> that possible or can ways not be reversed if the direction may not be
> changed in level 0?
>
> Also it would be good if adding {add mkgmap:has-direction=true}
> is only relevant for future lines if continue with_actions is used, but
> not if continue is used. E.g. if a road has cycleway = lane:left I display
> it only at resolution 24, however the road itself can be reversed. Just not
> the cycleway line that is a second line to the left side of the road. The
> road also is later in my style vs the cycleway. That way maybe some
> additional lines can be reversed.
>
> In general for Austria or Germany this gives pretty nice improvements in
> map size. For less developed countries the differences are smaller...
>
> On Tue, 11 May 2021 at 19:21, Gerd Petermann <
> gpetermann_muenchen at hotmail.com<mailto:gpetermann_muenchen at hotmail.com>>
> wrote:
> Hi Mike,
>
> it is off by default because it will cause trouble with some styles / TYP
> files which rely on the direction but don't set that the new special tag
> (yet).
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk<mailto:
> mkgmap-dev-bounces at lists.mkgmap.org.uk>> im Auftrag von Mike Baggaley <
> mike at tvage.co.uk<mailto:mike at tvage.co.uk>>
> Gesendet: Dienstag, 11. Mai 2021 13:15
> An: mkgmap-dev at lists.mkgmap.org.uk<mailto:mkgmap-dev at lists.mkgmap.org.uk>
> Betreff: Re: [mkgmap-dev] Commit r4703: improve RoadMerger (based on
> merge-roads-reversed-v6.patch)
>
> Hi Gerd,
>
> I may be misunderstanding this, but the explanation of when it is enabled
> seems illogical.
>
> It seems to me that reversing should be the default except on ways that
> have mkgmap:has-direction=true unless a switch is given to disable it.
>
> Or it could be off by default and a switch enables it, except for ways
> that have mkgmap:has-direction=true.
>
> Cheers,
> Mike
>
> -----Original Message-----
> From: svn commit [mailto:svn at mkgmap.org.uk<mailto:svn at mkgmap.org.uk>]
> Sent: 11 May 2021 11:22
> To: mkgmap-svn at lists.mkgmap.org.uk<mailto:mkgmap-svn at lists.mkgmap.org.uk>;
> mkgmap-dev at lists.mkgmap.org.uk<mailto:mkgmap-dev at lists.mkgmap.org.uk>
> Subject: [mkgmap-dev] Commit r4703: improve RoadMerger (based on
> merge-roads-reversed-v6.patch)
>
> Version mkgmap-r4703 was committed by gerd on Tue, 11 May 2021
>
> improve RoadMerger (based on merge-roads-reversed-v6.patch)
> This has two effects:
> - it allows RoadMerger to merge roads which build a sharp angle, if that
> is done an info message is logged
> - it allows RoadMerger to merge roads with different directions be
> reversing the order of points if special criteria are met
> - implement new special tag mkgmap:has-direction=true which tells mkgmap
> that the direction of the way is important and should not be reversed. The
> routing tags oneway=yes or oneway=-1 have the same effect, but they also
> effect routing. Use this tag if you have a TYP file which renders lines
> different (e.g. cycleway on the right or on the left side) to prevent a
> reverse merge
> - implements new experimental option --x-force-reverse-merge
>
> Merging with reverse produces smaller maps, esp. smaller NET and NOD
> files, it may have an influence on routing.
> Reversing of roads is disabled unless mkgmap detects that the style has at
> least one rule which adds mkgmap:has-direction=true in rule file lines or
> option --x-force-reverse-merge is used.
> The program checks if any line that was added for a given OSM way has the
> tag mkgmap:has-direction=true.
> If one is found the tag is propagated to the road(s) for that OSM way so
> no reversing happens.
> Roads with different direction attributes are not merged.
>
> The option --x-force-reverse-merge is meant for those who don't use a TYP
> file or don't render left/right attributes with different types. All others
> should not use the option and adapt the style instead.
>
> http://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4703
>
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>
> --
> Felix Hartman - Openmtbmap.org & VeloMap.org
>
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>
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