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

Wed May 12 18:12:21 BST 2021

Hi Mike,

Thanks for the reminder reg. rails.
The algo might work for them as well, at least for rails with two parrallel lines, maybe also if four lines fall together so that there is a pattern like  a-b-c-b-a-b-c-b-a . But, as I wrote, it will only remove invisible points so far, so only file size changes (and maybe rendering time)

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Mike Baggaley <mike at tvage.co.uk>
Gesendet: Mittwoch, 12. Mai 2021 18:47
An: 'Development list for mkgmap'
Betreff: Re: [mkgmap-dev] Commit r4703: improve RoadMerger (based on    merge-roads-reversed-v6.patch)

That sounds really promising Gerd. Does this only apply to roads, or can it
also handle other lines? I would like to also reduce multiple railway lines
to a single line at lower resolutions.

Cheers,
Mike

-----Original Message-----
From: Gerd Petermann [mailto:gpetermann_muenchen at hotmail.com]
Sent: 12 May 2021 16:56
To: Development list for mkgmap <mkgmap-dev at lists.mkgmap.org.uk>
Subject: Re: [mkgmap-dev] Commit r4703: improve RoadMerger (based on
merge-roads-reversed-v6.patch)

Hi Felix,

see https://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4711

I think I see a way to really improve rendering of dual carriage ways. Needs
some more experimenting. At the moment only size is reduced in
RemoveObsoletePointsFilter, but the new code seems to be able detect dual
carriage ways. Work in progress...

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 16:58
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev] Commit r4703: improve RoadMerger (based on
merge-roads-reversed-v6.patch)

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<mailto: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<mailto:mkgmap-dev-bounces at lists.mkgm
ap.org.uk>> im Auftrag von Felix Hartmann
<extremecarver at gmail.com<mailto: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><mai
lto: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
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ap.org.uk><mailto:mkgmap-dev-bounces at lists.mkgmap.org.uk<mailto:mkgmap-dev-b
ounces at lists.mkgmap.org.uk>>> im Auftrag von Mike Baggaley
<mike at tvage.co.uk<mailto:mike at tvage.co.uk><mailto:mike at tvage.co.uk<mailto:mi
ke 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><mailto
: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><mailto:svn at mkgmap.org.uk
<mailto:svn at mkgmap.org.uk>>]
Sent: 11 May 2021 11:22
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:mkgmap-svn at lists.mkgmap.org.uk<mailto:mkgmap-svn at lists.mkgmap.org.uk>>;
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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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