[mkgmap-dev] generate-sea option and faster-mp changes

Thu May 12 13:29:48 BST 2022

Hi Gerd

Looking at older versions (2019), createLandWay() makes a polygon with
the tile bounds; no extra. This hasn't changed since then.

createSeaWay() has flag to enlarge the polygon slightly and use of this
hasn't changed in the release version

Ticker

On Thu, 2022-05-12 at 08:37 +0000, Gerd Petermann wrote:
> Hi Ticker,
> 
> thanks, I'll take a look at it. My understanding was that
> SeaGenerator should produce an outer way which is slightly larger
> than the tile.
> Did I change that?
> 
> 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, 12. Mai 2022 08:20
> An: mkgmap development
> Betreff: [mkgmap-dev] generate-sea option and faster-mp changes
> 
> Hi Gerd
> 
> I've just rebuilt britain-and-ireland-latest.osm.pbf with the current
> trunk and find that many tiles on the coast have flooded rectangles.
> The coastline is all correct and these flooded area are normally well
> inland and unrelated to where the coastline crosses the tile
> boundary.
> 
> I use option
>   --generate-sea="multipolygon,extend-sea-sectors,close-gaps=750"
> and this worked fine up to about a year ago - I've only just noticed
> the problem.
> 
> Cutting this from a suitable area (Wales, UK, Britain, Europe etc)
> 
> 74220030: 2408448,-331776 to 2430976,-196608
> #       : 51.679688,-7.119141 to 52.163086,-4.218750
> 
> and building with minimal options plus above and default style should
> demonstrate the problem. There are also extra error messages starting
> 
> ... 030.osm.pbf: Multipolygon generated SeaPolygonRelation [nat...
> 
> in the log file, which I attach
> 
> I think it is related to the faster-mp changes and the MP structure
> SeaGenerator created. This has 1 outer (the tile) and all bits of
> land
> are inners, including land touching the edge of the tile.
> 
> I've attached a patch for an enhanced version of SeaGenerator that
> distinguishes between land/sea areas that touch the edge and true
> [anti-]islands and only use MP processing for the islands. With this,
> tiles are correct.
> 
> It also has other benefits: It is clearer in what is happening,
> doesn't
> do a lot of pointless tagging of ways that will joined to become
> polygons, etc
> 
> Ticker
> 
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