I have always wondered how anyone made a map without our modern technology. It's hard to wrap one's head around how ancient mapmakers could visualize what the world looked like from above just by traveling through it. The art of surveying has always been a mystery to me.
Chris Spargo got a chance to visit Ordnance Survey, the government agency in Britain that makes maps. They had a display of historical equipment used to make maps in the days before aerial surveys and GPS, which included a box for spiders. Why? Well, before we get to that, we learn some neat stuff about the advances in cartography over the last few hundred years, but eventually the spiders are explained. There's a one-minute skippable ad at 5:50. (via Damn Interesting)
Wednesday, October 08, 2025
Why British Cartographers Have a Box of Spiders
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As I understand it, it's done via sightings from a known point, of a known height. So, you can find how far you are away from the mountain, with known height, because you know the angle you need to use, to see the mountaintop. With two such known points, you can determine your distance and direction to both, which creates a triangle with you at the peak - hence, "triangulation". That means you can map features to the flat map, eventually, creating a picture as if from above.
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