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

Thu May 12 09:37:36 BST 2022

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