In movies, the first thing a person says when waking from a period of involuntary unconsciousness is: “Where am I?” For many of us today, though, knowing where we are is a job that has been outsourced to a technological prosthesis. The existence of phone-based mapping is a fabulous cyborg-era boon for people like me who have almost no innate sense of direction and who spent the pre-smartphone age marching out of buildings in exactly the wrong direction. Still, one easily forgets, when receiving infallible directions to a pub, just how extraordinary the GPS system is, dependent on 31 orbiting satellites and mathematical corrections for Einsteinian relativity. The problem is that, as Greg Milner’s fascinating book points out vertiginously, the comforting sense a GPS-equipped smartphone gives you – that you know where you are – is more fragile and fictional than it seems.
For a start, the faint radio signals intercepted from orbiting satellites are compared to maps that may or may not be accurate. (Hence the stories about people following GPS systems who drove off bridges: Milner collects these under the rubric “Death by GPS” but, as he knows, they would be more accurately described as examples of death by bad map.) For another thing, it is worryingly easy to “spoof” GPS receivers with false data, in order (as one relatively benign demonstration showed) to make a drone crash into the ground. And third, the very idea that there can be a totally accurate place called “where you are” is something of an idealisation when the ground is constantly shifting under our feet because of plate tectonics, on an irregularly shaped, sloshing and wobbling planet, the location of whose centre became known only relatively recently to within a centimetre. The exact location of the centre of the planet, it turns out, is important because all positioning must be defined relative to a reference point. The US military want to get that accuracy down to a millimetre. And yet even the centre of the Earth, defined as its centre of mass, wanders around because the distribution of water on the surface changes. “Nothing is where it seems,” Milner comments, “because it is nowhere.”
Like the internet (slaved to a GPS-enabled clock), GPS was originally a military technology. The first satellite was launched in 1978 and the system is still managed by the 50th Space Wing of the US air force. Its declared purpose at start-up was not navigation but guidance: telling missiles how to get to targets. The idea was to “drop five bombs in the same hole”, in large part because airmen were sickened by the destruction caused by carpet bombing in Vietnam. (As Milner asks, though: “What if you have the wrong hole?” Hence notorious mistakes such as the 1999 Nato bombing of the Chinese embassy in Belgrade: officials say the missile flew accurately to its destination co-ordinates but the CIA map used was out of date.) Yet it proved handy for military navigation, too: during the First Gulf War, GPS enabled what Milner calls “the first large-scale deep desert advance in the history of warfare”, allowing tanks and infantry to move with assurance in conditions where visibility often dropped to five metres.
GPS is embedded in many more places than bombs, planes (making it possible for pilots to land using instruments only), cars, ships and, these days, phones. Milner visits a beet farm in the US, a model of modern “precision agriculture”, where the tractor drives carefully automated, GPS-guided routes to plant and harvest beet without breaking the product. More vulnerably, GPS is now embedded in much of the “critical infrastructure” of the modern world, including the electricity grid and automated trading systems, both of which rely on GPS timing signals. A successful attack on trading computers could initiate a “flash crash” like that of 2010; an attack on the power grid could be much worse. “GPS has become our heartbeat,” Milner observes – and, just like a wifi-enabled pacemaker, it can be disrupted by malicious hackers.
Other people have particular reason to be GPS dissidents. American truck drivers, subjected to pervasive “fleet management”, involving the tracking of where they drive and precisely how long they stop for, buy “personal privacy devices” – or GPS jammers – that are freely available on the internet. In the UK, police do not need a warrant to put a GPS tracking bug on your car, and some see the increasing use of GPS-enabled electronic “tags” for convicted criminals as a wholesale replacement for the parole system. Of course, smartphone users are willingly carrying around their own electronic tags that transmit location data to whomever might be listening, and will soon even enable interested parties to know which shop in a mall a person has just walked into. GPS has a wide range of human uses, and yet society seems to have defaulted to the punitive panopticon.
On the other hand, there are now some GPS devices small enough to attach to a bee, which could enable remarkable insights into their swarming and dancing behaviour. And using very sensitive GPS sensors along with seismographs could give national disaster managers up to a few minutes’ crucial extra warning in the event of a large earthquake. (Both systems were in place before the magnitude 9.0 quake in Japan in 2011 but, as Milner explains, they were not joined up in the right way.) Measuring how the GPS signal travels through the atmosphere even improves weather forecasting by enabling an estimate of the quantity of water vapour around. Even space probes on the way to Mars must use Earthbound GPS as a reference point – as a Nasa engineer tells Milner: “We navigate the spacecraft by looking in the rear-view mirror.”
This is a deeply researched book with fascinating interludes on the history of navigation and geodesy (the measurement of the Earth). Milner has talked to many engineers who contributed to the present GPS system and its experimental forebears, and explains the technological principles lucidly. He also asks what we might be losing by relying so much on global positioning. He warns that it might be “altering the nature of human cognition”, rewiring our minds – but so does everything that we do habitually.
Milner opens and closes his book with a delicate and poetic account of the extraordinary mental system of navigation used by Polynesian islanders, the very possibility of which was disputed for centuries. If that capability is dying out, however, it is not the fault of GPS. Multiple experiments seem to indicate that people who use navigation systems remember less about the areas through which they have travelled, which does seem a shame. But I’d rather forget where I’ve been than never get where I’m going. Those of us who could never find our way around in the first place will still feel an intense, 21st-century comfort at seeing the blue dot on the screen that reassuringly means, more or less: “You are here.”
Steven Poole’s “Rethink: the Surprising History of New Ideas” is newly published by Random House Books
Content from our partners
Related
