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No. 2985:
Relative Accuracy

by Peter Turchi

Today, we'll question the virtue of accuracy. The University of Houston presents this series about the machines that make our civilization run, and the people whose ingenuity created them. 

Given a choice between an accurate map and a distorted one, most of us would choose accuracy. After all, accuracy is good, right? 

Well — it depends. "Accuracy," we need to remember, is relative. 

One of the great reminders of that fact is a map that's been used around the world for nearly a century.

The first underground railway opened in 1863. For 70 years, the map of the London Underground, or Tube, was simply superimposed over a road map. As the Tube expanded, that map grew increasingly difficult to read. The names of the stations in the center of the city were clustered together; the stations at the outskirts were so far apart that the map was unwieldy. The depiction of the lines and stations was accurate, but confusing.

MBTA map
The Massachusetts Bay Transportation Authority route mapPhoto Credit: Wikimedia Commons

A young draftsman named Henry Beck worked for the London Underground Signals Office. In his spare time, Beck made a very different map. He kept in mind the things passengers wanted to know: what line to get on, where to transfer, and when to get off. That may sound obvious; but it meant there were a lot of things passengers did not need to know. When we ride a subway, we don't particularly care if the next stop is a quarter of a mile away or half a mile; it doesn't matter to us where the track curves, or exactly what path it takes.

On Henry Beck's map, the rail lines were color-coded, and reduced to just a few simple angles.

Beck submitted his design in 1931. And it was rejected. 

Why? What made a map that's universal today seem so wrong to the people in charge of the London Underground?

Bangkok transit map
A Bangkok transit mapPhoto Credit: Wikimedia Commons

For one thing, it didn't look like a railway map — or at least, not the sort of railway map people were used to. It looked more like an electrical schematic, which was what inspired Beck —a kind of diagram that made a complex tangle of lines clear to the eye. For another thing, the map was inaccurate — instead of depicting the actual distance between stations, the map spaced the names so they were easy to read. To people working on the railway — the men improving the tunnels, providing illumination, maintaining track — the map was all but useless. But so far as passengers were concerned, the map was perfectly accurate: the individual lines were correctly identified, the stations were in the correct sequence.

Beck argued for his unusual looking map, and in 1933 it was adopted. The initial print run of 700,000 copies ran out in the first month.

Henry Beck
The plaque marking Henry Beck's birthplace in London.
Photo Credit: Wikimedia Commons

Henry Beck's transit map is used today by transportation systems from Korea to Vienna, from Montreal to Washington DC. It's considered one of the most effective maps ever made. But when it was first drawn, some people were quick to say it was wrong.

So the next time you're waiting for a train or bus'for that matter, the next time you ask what tomorrow's weather is going to be like, or what time it is, or how far you are from the next highway exit'think about which information, and how much information, you really want. Remember that 'accuracy' is nearly always a relative term. Like Henry Beck, we need to ask, accurate how? For what purpose?

I'm Peter Turchi, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

'Harry Beck and London's Iconic Tube Map.' Time Out London, April 17, 2007.

Turchi, Peter. Maps of the Imagination: The Writer as Cartographer, Trinity University Press, 2004.

Peter Turchi's most recent book is A Muse and A Maze: Writing as Puzzle, Mystery, and Magic. His other books include Maps of the Imagination: The Writer as Cartographer; Suburban Journals: The Sketchbooks, Drawings, and Prints of Charles Ritchie, in collaboration with the artist; a novel, The Girls Next Door; and a collection of stories, Magician. He has also coedited, with Andrea Barrett, A Kite in the Wind: Fiction Writers on Their Craft and The Story Behind the Story: 26 Stories by Contemporary Writers and How They Work; and, with Charles Baxter, Bringing the Devil to His Knees: The Craft of Fiction and the Writing Life. The recipient of fellowships from the National Endowment for the Arts and the John Simon Guggenheim Memorial Foundation, he is a professor of English at the University of Houston. His website is

Note added on Feb. 4, 2015: A listener wrote in response to this episode, concerned that it might make light of the topic, and raised some points that help develop the discussion. 

A subway map can be accurate with respect to the order of the stations but inaccurate with respect to the distance between stations. The challenge comes when we try to describe the accuracy of the map as a whole, as opposed to the accuracy of the map's individual components.

Accuracy is independent from utility. The lesson to draw from Beck's map might be that a map - among other things - doesn't need to be accurate to be useful; and in fact, for some purposes, an inaccurate map is more useful than an accurate one.

Finally, the listener suggested "accuracy is a binary condition"; something is either accurate or inaccurate. But if we take that to be true, no map is accurate. Every map chooses a projection, or distortion formula, to transfer some part of our three-dimensional world to a two-dimensional page.

While accuracy might be an absolute in some fields, we often use "accurate" as a word that accepts a modifier (more, less, etc.). Also, we define accuracy relative to a chosen objective. A darts player who hits the board ten times out of ten may not strike us as particularly accurate, if the goal is to throw a bullseye. On the other hand, if the darts player is standing 150 feet from the board, we might be impressed.

This episode first aired on January 15, 2015.