Ancestors

Written by Dave Anderson on 2024-10-26 at 17:07

I also love that GIS is a fractal of cursed things.

"Okay I could use a continent outline to draw stuff on"

• open box marked "continent outlines", ten million spiders pour out*

Ah, turns out some people have spent a large part of their lives on just the question of how to make coastlines look right. Cool cool good to know how delightfully cursed

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Written by Dave Anderson on 2024-10-26 at 17:12

If nothing else, a trivial thing I hadn't considered: tides. Coastlines aren't a constant feature even on a day timescale. OpenStreetMap standardizes on the coastline feature being "mean high water springs", the high tide line in spring averaged over the past 19 years.

There's a dedicated path in the OSM rendering pipeline just for producing the coastline+ocean backdrops, completely separate from the entire rest of the mapping logic, because it's just its own cursed little problem.

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Written by lolcat on 2024-10-26 at 17:16

@danderson

Is there a standard "ruler length" map people use for measuring squiggly lines?

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Toot

Written by Dave Anderson on 2024-10-26 at 17:21

@lolcat No idea! I assume a lot of coastline data comes from government survey data, at varying degrees of detail and accuracy. Part of the challenge of coastline representation, I'm told, is how to simplify the geometry as you zoom out without it looking weird or distorting shapes. Like, at what zoom level do you replace a cove with just a straight line? Last time I looked at this people had genuinely spent 10y of research on just that question, and it's still not fully solved.

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Descendants

Written by lolcat on 2024-10-26 at 19:35

@danderson

Love this sort of thing. It might sound like a technical question, but ends up touching on so many other things, including "the truth." E.g. a coastline measured with a 1m ruler would probably end up being many, many times longer than the same place when measured with 1km lines. So, how long is it? A? B? Something completely different? And that's just getting started.

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