[mkgmap-dev] closed ways and multi-polygon relations

Thu Nov 22 19:30:32 GMT 2018

Hi Ticker,

okay, I can reproduce the results. I was wrong, the ways with mkgmap:mp_created=true and mkgmap:stylefilter=polyline
are in fact copies of the original way members of the MP and those are typically not closed.
No idea why it is implemented this way. Looks wrong to me.

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Ticker Berkin <rwb-mkgmap at jagit.co.uk>
Gesendet: Donnerstag, 22. November 2018 19:16
An: mkgmap development
Betreff: Re: [mkgmap-dev] closed ways and multi-polygon relations

Hi Gerd

What I was expecting was that multiPolygonRelation generates 1 closed
way per distinct outer polyon and this has just the tags of the
relation. This is passed to 'lines' and 'polygons' matching.

My example is relation/1371699 which uses 9 ways (a mix of existing
roads and ways just created for the purpose) as outers to define a
single polygon.

What I'm seeing, with these in 'lines':

name='Littleton' & place=village & is_closed()=true {echotags
'lineLitVilTrue'}
name='Littleton' & place=village & is_closed()=false {echotags
'lineLitVilFalse'}
name='Littleton' & place=village [0x12 resolution 22]

1/ is no output from lineLitVilTrue

2/ 9 identical ways from lineLitVilFalse; I've removed some admin tags:
Way generated from 1371699 [landuse=residential,
mkgmap:cache_area_size=99714.294, mkgmap:mp_created=true,
mkgmap:stylefilter=polyline, name=Littleton, place=village]
lineLitVilFalse
Way generated from 1371699 [landuse=residential,
mkgmap:cache_area_size=99714.294, mkgmap:mp_created=true,
mkgmap:stylefilter=polyline, name=Littleton, place=village]
lineLitVilFalse
etc

3/ using GPSMapEdit, the generated line looks to be in 4 segments, some
of the outers from the relation have been joined, but it looks like it
has avoided joining where the base way tags conflict.

With this in 'polygons':
name='Littleton' & place=village {echotags 'polyLitVil'}
 and, as in default style:
place=village [0x03 resolution 22]

I get:
JoinedWay generated from 94665254 [landuse=residential,
mkgmap:cache_area_size=99714.294, mkgmap:mp_created=true,
mkgmap:stylefilter=polygon, name=Littleton, place=village] polyLitVil

which is as expected, and it shows correctly on the map.

I'm pretty sure the relation and have just loaded the latest data from
geofabrik .

I get about 4500 messages running 1 map tile with this in 'lines':
mkgmap:mp_created=true & is_closed()=false {echotags 'mpNotClosed'}

Ticker

On Thu, 2018-11-22 at 16:18 +0000, Gerd Petermann wrote:
> Hi Ticker,
>
> I don't understand what you expect here. The ways with tag
> mkgmap:mp_created
> are the result of the joining process. Normally they are closed.
> Is the one way that is reported a part of a broken MP?
> Maybe you expect that the members of a MP rel do also have a special
> tag?
> That would be something that you have to do in the relations style
> file.
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag
> von Ticker Berkin <rwb-mkgmap at jagit.co.uk>
> Gesendet: Donnerstag, 22. November 2018 17:03
> An: mkgmap development
> Betreff: [mkgmap-dev] closed ways and multi-polygon relations
>
> Hi Gerd
>
> I'd hoped and expected that all polygons were fed into the 'lines'
> style processing in a similar manner, regardless of their origin as
> either a closed OSM way or generated by multiPolygonRelation. This
> would allow simple testing using just 'is_closed()=true' to effect
> lines around polygons if required.
>
> Instead I find that, for a few examples I've looked at in detail, for
> each outer way in a relation a way is passed into 'lines'. They all
> have identical tags (from the relation) and is_closed()=false. It is
> difficult to determine if these correspond directly to the ways in
> the
> relation.
>
> In the generated map, the line around the area might be in multiple
> segments, so some logic appears to have merged some of the ways but
> not
> others. In my example is seems as if merging has been prevented when
> the original ways have conflicting tags (maybe just the name=)
>
> Given that it isn't possible to differentiate the multiple outer ways
> when passed in from multiPolygon, why doesn't it just pass in the
> joined way that will be passed to the 'polygons' processing.
>
> Also, assuming that later processing is joining some of these parts,
> what stops it joining them all.
>
> I can give you details of my example if required, but just having:
>
> mkgmap:mp_created=true & is_closed()=false {echotags 'mpNotClosed'}
>
> in 'lines' then looking for consecutive identical 'Way generated
> from...' output and checking that there is only 1 output polygon will
> yield a lot.
>
> Another difference between closed ways and multi-polygons is that
> with
> a closed way the object is passed through the rules of 'lines'
> concatenated with 'polygons' and all the facilties of stopping after
> a
> match/continue/with_actions work in a nice way, whereas with a multi
> -polygon, even if it matches in 'lines', it is passed through
> 'polygons' as well; so extra conditions will is needed in 'polygons'
> to
> determine if matched in 'lines'
>
> Regards
> Ticker
>
> _______________________________________________
> mkgmap-dev mailing list
> mkgmap-dev at lists.mkgmap.org.uk
> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
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