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

Wed May 12 14:08:23 BST 2021

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> 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> im Auftrag von
> Mike Baggaley <mike at tvage.co.uk>
> Gesendet: Dienstag, 11. Mai 2021 13:15
> An: 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]
> Sent: 11 May 2021 11:22
> To: mkgmap-svn at lists.mkgmap.org.uk; 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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