# Dr. Voronoy and the Bell System

Let me start this off: I’m not really good at math. This is a post about math. Cool? Cool.

There’s a thing called Voronoi diagrams. You take a plane, define points onto it, and map regions onto it to ensure the most efficient coverage or… something like that. Any given arbitrary point on the plane will be in a region that belongs to the closest defined point.

They’re the brainchild of Dr. Georgy Voronoy, though the concept predates him by a bit. The modern mathematical definition is his.

Because we’re a bunch of phone nerds, a few friends and I are trying to get a good idea of the boundaries of wirecenters (what used to be exchanges) in Seattle. I tried pulling public records of exchange maps but it turns out these days all of Seattle is considered one exchange.

We’ve been talking about starting with known boundaries, doing spot checks, mapping it out, then a friend suggested basing a Voronoi diagram on those.

Instead, I tried one based on the wirecenters I do know about. And it’s really good.

Emerson is up north, Sunset is over in Ballard, and Lakeview is next to I-5. The vertex at the bottom center is there because I put Atwater on the map. This is pretty much accurate. 99 does mostly define the Sunset/Lakeview boundary, and I did a spot check — the Sunset/Emerson boundary pretty much follows that line, though it’s a little too far north. It actually goes straight down the ravine you can see there, which makes sense. Also, Sunset ends at the ship canal. Naturally. But Northgate Mall has an Emerson number, and the medical plaza just south of it has Lakeview numbers.

You know what else is cool? That vertex, the one created because I put Atwater on the map, is very close to the Sunset/Melrose boundary. There’s no Melrose wirecenter anymore — it was rolled into Campus (which isn’t on this map because I forgot — imagine a line at 50th) decades ago — but 63x numbers remain.

Back to Voronoi diagrams. The Bell System was nothing if not cheapskates, in the best way. They paid for the brightest and best to save tons of money on the operations side. So, check it out: Emerson is placed just right so that its boundary with Sunset is this huge ravine that cuts through the North Seattle shoreline.

I placed a few other wirecenters I know about (it gets fuzzy downtown — there are a lot of wirecenters I didn’t place, because there are like ten), and well:

I’m not 100% sure how accurate this is. But. Campus did eat Melrose, and Melrose does include a lot of the Wallingford neighborhood, so that’s right.

Anyway, check that out. Look at where West is placed, optimal coverage of West Seattle. Cherry (bottom center) and Duwamish (Georgetown) define a line right along the ridgeline against Parkway. I missed another wirecenter in White Center or Delridge or so, which should put the boundary with Duwamish right on the Duwamish River. Which makes Duwamish’s area look pretty small and sparsely populated, until you realize the Duwamish exchange was originally built just to house a №5 Crossbar to be Boeing’s PBX.

Maybe I’m just doing that human thing where we like to see patterns in things, or maybe this is something Pacific Northwest Bell actually based exchange locations on back in the day.

I like the idea that a lot of the layout of our modern infrastructure is thanks to the work of a Russian mathematician.

Anyway, just another post on the magic of the mundane.

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