[mkgmap-dev] low-res-opt branch: error message from ShapeSplitter for self-intersecting multipolygon

Mon Jun 7 10:24:57 BST 2021

Hi Ticker,

okay, no problem, I'll work on the faster-mp branch in the mean time
Maybe I'll merge it first into the low-res-opt branch.

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Ticker Berkin <rwb-mkgmap at jagit.co.uk>
Gesendet: Montag, 7. Juni 2021 11:23
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev] low-res-opt branch: error message from ShapeSplitter for self-intersecting multipolygon

Hi Gerd

The shape I'm getting in my build has a major problem with a twist
between the 2 parts. I'm having trouble reconciling it with the OSM
map. I've attached the original shape trace.

I agree that some of the messages do need tweaking, but, in this cases
there is a significant problem.

I'll consider the types of messages etc in the new version I'm working
on.

I'm away for a few days and won't be able to do much remotely.

Ticker

On Mon, 2021-06-07 at 07:22 +0000, Gerd Petermann wrote:
> Hi Ticker,
>
> please check https://files.mkgmap.org.uk/download/512/63240024.o5m
> with (unpatched) r4756 and these options --generate
> -sea=multipolygon,floodblocker --preserve-element-order --order-by
> -decreasing-area
> --allow-reverse-merge
>
> Produces an error message
> SCHWERWIEGEND (ShapeSplitter):
> e:\osm_out_work\norway\20210511_095323\63240024.o5m: Vertical split
> 36691968 failed on shape at
> http://www.openstreetmap.org/?mlat=65.979056&mlon=12.308790&zoom=17 P
> ossibly a self-intersecting polygon
> for this invalid multipolygon :
> https://www.openstreetmap.org/relation/5294624
>
> The result doesn't look wrong, so I think there should either be no
> error message or we need code to remove those self-intersections or
> ignore invalid MP like that?
>
> Gerd
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