[Tagging] coastline v. water

Frederik Ramm frederik at remote.org
Mon Nov 23 19:53:06 UTC 2020


I would like to make one point that has been touched on but not said
clearly, I think.

Some proponents of the recent changes to Chesapeake bay have used
reasoning like: "Only by mapping the bay as a polygon can $SOFTWARE
properly determine that a given location is in the bay, as opposed to in
some undfined part of the sea."

To this, Jochen has even replied along the lines of "create a polygon if
you want but additionally use the natural=coastline tag".

I want to issue a stern warning here: This line of thinking will not
stop with Chesapeake bay. People are already creating giant
multipolygons for the Strait of X and the Gulf of Y all over OSM. Before
too long, a desire to have $SOFTWARE properly decide that a given
location is, say, in the Atlantic Ocean, will give rise to demands that
the Atlantic Ocean be mapped as a giant, named water polygon.

Our current tooling makes this impractical (that's the very reason why
we handle the coastline like we do). Even the 2000+ member "gulfs" and
"bays" and "straits" that some people seem to derive endless pleasure
from plastering the map with - often using questionable third-party
sources or guesswork to define where exactly you leave the ocean and
enter the gulf - already complicate the delicate community processes of
editing and quality assurance. Splitting a single piece of coastline
anywhere along Chesapeake bay now will, for example, give your changeset
a bounding box that encompasses the whole bay. Anyone monitoring local
edits gets swamped with false positives like that. It will also require
uploading a complete new version of the giant bay polygon, vastly
increasing the likelihood of edit conflicts that might well lead a
hapless novice to abandoning their work, rather than trying to solve the

Now, you might smirk and say "let's fix the tools then", but until the
tools are fixed - which might take years -, you've made life a hell of a
lot harder for anyone editing or quality monitoring in the whole area.

And all for what - a nice blue label in the bay?


Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"

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