The map that stopped being literal.

A street map and a subway diagram answer different questions. Walking above ground, you need to know where streets actually bend and how far apart places are. Underground, you may mostly need the order of stations and the point where you change trains. Trying to preserve every kind of truth on one sheet can make the sheet worse at its main job.

In 1931, electrical draughtsman Harry Beck worked on a diagram for the London Underground. The design reached the public in 1933. Instead of tracing every geographic curve, he organised routes using verticals, horizontals and 45-degree diagonals. The River Thames remained as a simplified geographic reference. The map was not pretending that London had become a tidy machine. It was selecting the relationships a passenger needed to see.

Beck's approach makes a useful distinction: a diagram can be inaccurate about distance while being highly useful about connection. That does not make distortion universally good. You would not want to use a transit schematic to estimate a walk without checking a geographic map. The design question is what the reader is trying to do next. Apply it to a presentation, a timetable or an instruction screen: which details help someone act, and which merely prove how much you know? Removing a detail can be an act of care when the important relationship becomes easier to see.