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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Toot

Written by Dave Anderson on 2024-10-26 at 17:15

And then the readme goes to great lengths to say that most of the work it does is to ensure the coastlines are closed polygons, because the rest of the GIS pipeline requires them to be.

And then immediately says "except Antarctica, because in most projections it ends up being an open polygon, so there's hardcoded special cases for Antarctica to allow it to be an open polygon that gets closed using projection-specific hacks"

Mapping is like Unicode, deeply human and intricate and flawed ❤️

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Descendants

Written by Dave Anderson on 2024-10-26 at 17:18

I think I'm finding that I love these corners of computing that are about engaging with the real world and human systems, with all their history and traditions and exceptions. Where every broad statement comes with at least one asterisk, and that asterisk could be an entire master's thesis by itself (and probably was!). In a time where venture capital is busy trying to make humanity more computable, projects like Unicode and OpenStreetMap try to teach computers about humanity. It's beautiful.

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Written by Dave Anderson on 2024-10-26 at 17:34

I also love that, in general, the articles on OSM wiki in German are 10x more detailed than the ones in English. National stereotypes are silly and unhelpful, but also there is definitely a meta-commentary here about the relative devotion to order and organization in different cultures. OSM owes a great deal to its German contributors.

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Written by Dave Anderson on 2024-10-26 at 17:46

Speaking of, the German OSM article on coastlines has some great little statements in it. (machine translated into English, because my German is quite poor)

Coastlines are not cartographically trivial.

When exactly does a coast turn into a river?

When does an artificial construction belong to the coast? [link to immense article about mapping ports]

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Written by Agnieszka R. Turczyńska on 2024-10-26 at 17:24

@danderson How the renderer treats objects like causeway to Lindisfarne?

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

@agturcz That's a human construct, so both OpenStreetMap and Google seem to represent it as a road segment, separate from the continent layer.

... I think, I would have to go digging into the OSM backend to check exactly what the feature is, but it's being rendered as a street.

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Written by Dave Anderson on 2024-10-26 at 17:28

@agturcz But there are plenty of natural features like that, which are part of the complexity of coastlines. Another is archipelagos of islands that are close together, as you zoom out you end up having to lie and distort the shapes of the islands to maintain a visual separation between them, because the eye dislikes "oops these are all one island now" much more than "I'm lying about the shape and area of these islands so that you can still perceive a tiny bit of water between them"

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