[Tagging] Using multipolygons to map bays in Alaska

Frederik Ramm frederik at remote.org
Sat Nov 17 11:27:51 UTC 2018


On 11/17/18 01:51, Paul Allen wrote:
> I'd find that bad enough even had he been right in his interpretation. 
> Given how he has explained
> it so far,


Jumping back in here after a while, and assuming that the "he" here is
talking about me, let me offer a bit of backstory and explain why I am
unhappy about all this.

I'm doing a fair bit of map rendering myself, using a wide array of
different map styles, either self-made or made by others, and including

OSM-Carto does two particular things with water rendering that not every
map necessarily does:

1. They use the same colour for the sea as for inland water areas.

2. They don't actually draw sea polygons; they have a blue map
background and then draw the land mass in grey on top of it.

While the wiki has been advising against rendering natural=bay in a
solid blue fill for a while (actually since Chris Hormann added a note
to that regard in January 2016), it used to make sense to disregard this
advice because you'd have many natural=bay areas that were not on the
sea but adjacent (e.g. Botany Bay used to be like that for a long time)
giving you white spots on your map otherwise. (OSM-Carto wouldn't have
this issue because their background was blue, but if you chose to have a
white map with sea polygons drawn you'd see it.)

So, long story short, a couple of "my" maps suddenly started to show
ugly dark-blue patches e.g. across the bay of Biscay, or the Gulf of
Bothnia. That's how I noticed and investigated what was happening, and I
found that Daniel had added the Gulf of Bothnia polygon to accompany the
newly-introduced OSM-Carto feature of rendering bay names depending on
the size of the area.

Of course I can adapt my map styles, and have indeed done so, as I often
have to do when mappers change their behaviour. But I was pissed off
nonetheless; I felt that OSM-Carto is just one rendering project and
does not (and should not) have the authority to steer what mappers do.
There are many other people interpreting our data and they should not be
forced to jump whenever OSM-Carto decides they want to change something.

I do agree that while we should not "map for the renderer" it is good to
have a central map that provides valuable feedback, and keeps mappers
from, say, introducing random highway types by simply not rendering
them. But I felt in this situation, they had overstepped their mandate,
*especially* because they were not reacting to something that people
were doing, but actively creating a new feature ("hey, you can now have
huge named bays") and at the same time adding the data to OSM to
illustrate their new feature.

Another pet peeve of mine is a dislike of what I call "relation mania",
where we have land boundaries that can easily be part of 20 different
relations on different admin levels and other boundary types. It's bad
enough on land, and makes editing harder for everyone; when I saw the
Gulf of Bothnia polygon (which *already* is large enough for the web
site to time out when you want to show the history) I thought: Is this
*really* necessary if all you want is a nice label written on the sea?
And let's be totally clear here: A nice label on the sea is all that
Daniel wanted. He's not a maritime scientist who for some reason needs
the exact extent of Bothninan Bay - he went through the time-consuming
exercise of combining more than 1600 coastline pieces into one huge
polygon which is difficult to handle for data processors and editors

It is only a matter of time until they start labelling natural=sea
polygons and people then create relations with 100,000 members for the

If you are not interested in labels, then this is wrong because of the
side effects.

If you *are* interested in labels, then this is wrong because (a) it
means that you have to go through this huge exercise just to place a
label, and (b) the label will vanish as soon as someone breaks the
polygon by e.g. creating a small self-intersection along one of the 1600
coastline bits. It will probably be gone more often that it is there.

Summing up, my opinion is

(1) the OSM-Carto project and Daniel have overstepped their mandate as
the maintainers of our style, and should have sought a wider consensus
on this before acting;

(2) the decision they have made is not a good solution for the
cartographic problem they wanted to solve;

(3) the decision they have made will lead to people creating huge
polygons that will often break, make coastline editing harder, and have
at least one totally made-up edge.

And, I have to admit,

(4) Frederik has been an utter dick to try and start the discussion by
deleting the Bothany Bay polygon, instead of simply raising it here. It
was wrong, I'm sorry.


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

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