Adding the Gulf of Bothnia as a 1600+ member multipolygon creates a pseudo precision that does not match reality, and needlessly complicates all coastline editing. The way drawn in as the "southern boundary" is arbitrary. A node is perfectly sufficient.
Could you explain what do you mean by "it does not match reality"? Is there something not real with gulf being limited by the coastline - other than coastline not being accurate in itself (which is the real source of what you called pseudo precision)?
Southern line was just first approximation (straight line), it should be drawn more precisely over time.
I should have been more precise; it is a random subset of reality. The gulf is part of the baltic sea which is not mapped as a named polygon. The gulf consists of smaller named water bodies, namely the "Bothnian Bay" in the North, and the "Bothnian Sea" in the South. These are not mapped as polygons either, and these themselves partly consist of smaller named water bodies like Luodonselkä in the North-East. My point is that the "Gulf of Bothnia" polygon has been arbitrarily been introduced for rendering purposes at a specific zoom range, to have a nice name showing on the map.If you step into the water on the Eastern shore of Hailuoto island, you are stepping
into the waters of Luodonselkä. And into the waters of Bothnian Bay. And into the
Gulf of Bothnia. And into the Baltic Sea. Things will be similar elsewhere. Selecting one of them to create a polygon for is arbitrary and not an accurate representation of reality. I think that it is desirable to record the names and
approximate locations of these water bodies, but we *must* find a better solution
for it than to create massive polygons with thousands of coastline member ways for
each of them. These massive polygons make editing the coastline harder, they are liable to break
at any time, they often suggest a precision that does not exist in reality,
and they're also a burden on data processors down the line.
I forgot to mention that if someone *did* want to properly map the Bay of Bothina and the Bothnian Bay and Luodonselkä, these would be three partly overlapping natural=bay objects which would likely cause editor warnings and mis-countings ("hey, OSM has so-and-so many square kilometres of bays mapped"). But as I said, it's undesirable to have each piece of coastline be part of 20 relations anyway.
The latest thread about bays on the Tagging list is much more generic than this case, so it's better to discuss it here:
@woodpeck Do I understand you correctly that you deleted a sea area polygon because other sea areas nearby haven't been mapped (yet?) as polygons?
I agree that the boundary line is likely not precisely defined (in reality), but discussing this with the creator before deleting it completely would maybe have been more sustainable. You write that nodes are "sufficient", but how can you understand the size/extent of the area from the node?
How can you see that "The gulf consists of smaller named water bodies, namely the "Bothnian Bay" in the North, and the "Bothnian Sea" in the South. ...and these themselves partly consist of smaller named water bodies like Luodonselkä in the North-East." if these are all "perfectly sufficient" nodes?
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