The battle for territory in digital cartography

IN THE 1940s Jorge Luis Borges, an Argentine writer, wrote a short story about mapping. It imagines an empire which surveys itself in such exhaustive detail that when unfolded, the perfectly complete 1:1 paper map covers the entire kingdom. Because it is unwieldy and thus largely useless, subsequent generations allow it to decay into tatters. Great scraps are left carpeting the deserts.

In their capacity for up-to-the-minute detail, modern maps surpass even Borges’s creation. By using networks of sensors, computing power and data-crunching expertise, digital cartographers can produce what are in effect real-time simulations of the physical world, on which both humans and machines can base decisions. These maps show where roadworks are blocking traffic or which street corners are the most polluted. Innovative products will make new demands of them. Drones need to know how to fly through cities; an augmented-reality game might need to know the exact position in London of Nelson’s...