Someone mapped every lighthouse on the planet. They run on a design system older than the web.

What can a century of lighthouses teach people who build design systems?

This week, I found a map I keep looking at.

It is a night globe. Spin it, and you see the lights along the coastlines of the world flicker, not as a glow, but as thousands of independent lights, blinking and sweeping their beams in individual rhythms. Zoom in on the coastline, and you see lights in the harbours. Hover over one of them, and it tells you its name.

There are 75,919 lights on this map. Each of them flashes at the rhythm printed on the chart.

This tool is called mapped.earth, and it was created by Aaron Becker, a generalist whose background is in institutional asset allocation and who enjoys solving problems by writing code. Aaron created it with open data: OpenSeaMap and OpenStreetMap contributors, the NGA List of Lights, NOAA charts, and the USCG Light List.

There are also 29 separate maps showing individual coasts. There are 263 lights in Japan, 245 in Brazil, 237 in Germany, 225 in Mexico, 188 in Scotland, 158 in England and Wales, and 26 in Florida. On every coast map, each beam is shadowed by the land it guards, and you can hover over any light to see its name, its character and its range.

It is a beautiful piece of work. But after spending some time with it, I realised that what I was looking at was something very familiar from my own work.

A design system.

Every light has a code

Each light isn’t just a light. It is a light that flashes in a specific pattern, and the pattern is documented.

On the chart, it looks like this: Fl(2) W 10s.

Fl stands for “flashing”, and the (2) stands for “a group of two flashes”. W stands for “white”. And 10s is the period: the whole sequence repeats every 10 seconds. Two white flashes, then darkness, then again.

Every light is described by three elements: its colour, its period, and the pattern within that period. Flashing, occulting, isophase, quick, even Morse code. A small, strict vocabulary, and everything is built from it.

The reason is very simple. At night, from a ship, all lights look the same. They are all just dots in the dark. The only way to tell one light from another is its rhythm. So different lights use different colours, frequencies and patterns, so that a sailor can recognise them.

This is a token. A short, named value that means the same thing wherever it is used.

Every system needs a rulebook

These patterns are not invented light by light. There is an international organisation behind them, the International Association of Marine Aids to Navigation and Lighthouse Authorities, IALA, and it publishes recommendations.

Some of them are surprisingly strict. A single flashing light should be lit for less than two seconds in each period. When flashes come in a group, each flash should last the same time. A long flash needs a period of at least eight seconds.

Some patterns have a reserved meaning. For example, a group of two white flashes, Fl(2), marks an isolated danger. Cardinal marks, which tell you which side of a hazard is safe, follow a clock face: three flashes for east, six for south with a long flash, nine for west. Once you know it, there is no way to forget it.

But one pattern is missing on purpose. IALA’s buoyage system does not use a steady light at all, because a light that never changes cannot be told apart from other lights.

A component left out of the system because it fails the test that really matters. I’ve had that conversation in design reviews several times.

Every system has a version history

Lights do change, and the changes are documented.

Haulbowline Lighthouse sits at the mouth of Carlingford Lough in Northern Ireland. It was completed in 1824 with a fixed light. In 1899, its pattern changed to three flashes every 30 seconds. In 1922, it changed again to three flashes every 10 seconds. That pattern is still used today.

This is a release history. Same component, three versions, a hundred years apart.

And every system drifts a little

There is one more thing I love here, and anyone who works on design systems will recognise it immediately.

The notation is not completely consistent. It varies slightly from one country’s List of Lights to another, with dots added or removed. Same meaning, different syntax, depending on who wrote the documentation.

Even a system built for life and death drifts a little with its naming.

What we learn

Most of the design systems I have seen were judged on how consistent they looked. This system is judged on whether a tired person on a moving ship can tell one light from another in the dark, within a few seconds, without any mistakes.

It is a harsher test. And the priorities become very obvious. Distinguishability trumps decoration. Each pattern has to be distinct enough from the patterns around it to be recognised under stress. Patterns repeat around the world. Lampione, a tiny light off Sicily, uses Fl(2) W 10s, like many other lights. What matters is that it cannot be confused with the lights near it.

It is the same thing I keep coming back to when I write about aviation: systems where making a mistake is not an option tend to be the clearest systems we have.

Lighthouses have been running on tokens, guidelines, reserved meanings and version histories for more than a century. Decades before the web, and long before anyone thought of it as a design system.

Aaron’s map just makes it visible. Go and spin it. Then pick any light and read its code.

Designing for complex enterprise systems changed how I work entirely. If you want the full breakdown of my design and dev workflow, I put it in an 18-page guide: How We Ship Without Figma.

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References

• Every lighthouse in the world and Lighthouses, live. mapped.earth, Aaron Becker.
• About mapped.earth.
• Light characteristic. Wikipedia (IALA recommendation R0110, notation, fixed lights, isolated danger marks).
• Lights, buoys and navigation aids. Sailing Issues (characteristics, cardinal marks).
• Lighthouses Directory. Marine Radar (IALA notation, Fl(2) W 10s).
• Haulbowline Lighthouse. Wikipedia.
• Lampione Lighthouse. Wikipedia.

Someone mapped every lighthouse on the planet. They run on a design system older than the web. was originally published in Bootcamp on Medium, where people are continuing the conversation by highlighting and responding to this story.