After a vacation at the Baltic Sea I noticed that the coastline in OSM is no longer matching the reality. I tried to fix this yesterday but the rendering of the map looks awkward but I cannot find anything strange looking at the data, neither in JOSM nor in iD.
Could anyone with deeper knowledge in coastline mapping have a look please?
For OpenStreetMap Carto there can be significant delays between changes being made to the high water line and its appearance on the map. This can be easily several days.
Coastline rendering in Standard tile layer on openstreetmap.org may update later than other rendering changes. There are two reasons for this:
To avoid major disruptions of map rendering due to data errors (entire continents displayed as sea instead as land) the coastline is not automatically updated if there are larger changes in the geometry compared to the last time it was successfully processed. For example any addition or removal of a large lake with coastline tag will require manual intervention. This is done to avoid entire continents being flooded because someone broke small coastline section. You can look at the update times of the layers on Land polygons to see when the last successfull update of the coastlines was done.
Internal coastline map lists new major changes to coastline which were not yet validated
Normally changes in OSM data will be detected by the update process on the tile servers and affected tiles will be marked as to be updated. This does not always happen correctly for coastlines. The problem is that the need for the update might be detected and a re-rendering scheduled, but if at that time the new coastlines aren’t available (see above), it will re-render the old coastlines. So sometimes it needs further changes to trigger the re-render again.
Oh, thank you very much for your fast reply. I thought that coastlines could be something special for rendering but did not expect it to take more than 10 hours.
As I am new to coastline mapping I just feared that I destroyed something and that this error could progress into offline maps.
It looks OK - and if you are worried you can try to check with JOSM validator (Osmose exists and likely will work fine for coastline, but it also report many spurious, completely unimportant or wrong errors).
Thank you to the OSM users who have been maintaining the Coastline by hand for many years without much fuss. Countless times they have saved entire continents from flooding.
