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[mkgmap-dev] Bug in Road Merging - actually doubling roads.

From Gerd Petermann gpetermann_muenchen at hotmail.com on Fri Feb 23 07:21:47 GMT 2018

Hi Felix,

I have to think about this for a while. There are three very short ways connected in node 412440328:
way 130665733 : the northern node 1263658617 is close to a Garmin grid point, the sourthern node 412440328 is also closer to this grid point than to any other,
so both are rounded to the same grid point in the north, and finally it is ignored.
way 110722884:  the way is only ~1m long and  both nodes are far from any Garmin grid point. This is the way that is causing the trouble.
It is not removed, instead the initial rounding changes it to a ~3m way  going north -> south.
way 130663479: the way has 3 nodes, and the one in the middle (node 1263658804) is rounded to the same coords as the ends of the bridge (way 103567847) and way 110722884, while the northern node 412440328 is moved up.

I've attached 4 files to document the problem. Please load into JOSM to visualize:
orig.osm.pbf: the original osm data 
init_hp.osm.pbf: the road network as input to WrongAngleFixer in so called "high precision"
init_mu.osm.pbf: like init_hp.osm.pbf, but rounded to Garmin map units
after-WO_mu.osm.pbf: the result of WrongAngleFixer with coords rounded to Garmin map units
(please ignore the fact that the node ids in non-orig files are wrong)

Somehow I have to teach mkgmap that it would be better to ignore (also) way 110722884. I don't know yet what criteria I should use for that.
Normally we try to keep all routable ways, as they may contain access restrictions. 

BTW: There is more such trouble near way 111528851.


Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Felix Hartmann <extremecarver at gmail.com>
Gesendet: Donnerstag, 22. Februar 2018 20:19:15
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev] Bug in Road Merging - actually doubling roads.

Perfect. I guess my maps are the only one causing bsod here on devices, but without the bug they would be fine...

On 22 Feb 2018 20:03, "Gerd Petermann" <gpetermann_muenchen at hotmail.com<mailto:gpetermann_muenchen at hotmail.com>> wrote:
Hi Felix,

I can reproduce the problem with a small download around the way and just the --route option.
The problem seems to be in WrongAngleFixer, it says
"... all points of way http://www.openstreetmap.org/way/130665733 are rounded to equal map units"
No idea why the way is not reduced to a single point, will investigate further.


Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk<mailto:mkgmap-dev-bounces at lists.mkgmap.org.uk>> im Auftrag von Felix Hartmann <extremecarver at gmail.com<mailto:extremecarver at gmail.com>>
Gesendet: Donnerstag, 22. Februar 2018 19:27:44
An: Development list for mkgmap
Betreff: [mkgmap-dev] Bug in Road Merging - actually doubling roads.

I just noticed that mkgmap sometimes creates a lot more routable roads for a certain stretch than actually defined in the style-file.


should be only once as a routable line in my map, however it ends up 6 times!
Once is correct, but 5 iterations are actually the way from the south (3 times) and the way from the East (2 times). Now each of these ways should be created that often, however it should not overlay into this short stretch of way.

While doubling up ways can be beneficial for routing, having a way more than 5 times on top of each other let's Garmin devices crash on routing over them. Also it leads to detours - as it will not always route straight from the Way from South to the Way going to the West, but follow along after the intersection for 4.3m until hitting up north, then reversing and finally going to the way in the West.

I've uploaded the tile here:

I'm pretty sure that with other style-files - the way will also be copied past the intersection and end up too often in the map for that 4.3m stretch...

I kinda guess it is related to it being so short - that place has some remarkable micro-mapping detail.
Or is this really expected?

If needed I can try to create a reduced style to only create that problem - but I think the bug should be obvious.

Felix Hartman - Openmtbmap.org & VeloMap.org
Schusterbergweg 32/8
6020 Innsbruck
Austria - Österreich
mkgmap-dev mailing list
mkgmap-dev at lists.mkgmap.org.uk<mailto:mkgmap-dev at lists.mkgmap.org.uk>
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