In August, a man with a sword was arrested near Buckingham Palace on suspicion of preparing to commit an act of terrorism. Westminster Magistrates Court heard that the man, an Uber driver from Luton, had intended to go to Windsor Castle but his satnav directed him to a pub called The Windsor Castle instead. Without stopping for a drink, he drove on to Buckingham Palace. It isn’t clear if he was still relying on the satnav for the final stage of his journey, or whether rage at the mistake was a motivating factor in his alleged offence. Three police officers were said to have received minor injuries; presumably he hadn’t stopped to ask them for directions.
Greg Milner includes a few stories about satnav fails in Pinpoint, his lively history of satellite navigation technology – his central chapter is called ‘Death by GPS’ – but one of the eye-opening things about his book is quite how far-reaching the tech is. As well as guiding missiles and encouraging motorists not to pay attention to road signs or even to the road ahead of them, GPS is used in crop management, high frequency trading, weather forecasting, earthquake measurement, nuclear-detonation detection and space exploration, as well as the smooth running of countless infrastructure networks, from electricity grids to the internet.
GPS, which stands for Global Positioning System, was developed by the American military. The US Department of Defence currently spends more than a billion dollars a year maintaining it. There are 31 GPS satellites orbiting the earth, all monitored, along with hundreds of other military satellites, from Schriever Air Force Base in Colorado. For the system to work, a receiver on the ground – your mobile phone, for example – needs to have a ‘line of sight’ to at least four of the satellites (there are very few places on earth where it wouldn’t). Each satellite continously broadcasts its position, along with the time the signal left the satellite. The time it takes for the signal to reach you (measured in milliseconds) will tell you exactly how far away it is. Three of these signals provide enough information to pinpoint your position; the fourth confirms the time used in the calculations. GPS satellites, unlike mobile phones, carry super-accurate atomic clocks, which are continually synchronised with one another. This is necessary for the precision of the positioning system, but many of the applications of GPS make use of it primarily as a timekeeping device.
Since 1967, the second has been defined as ‘the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom’. A pendulum clock uses gravity to make a pendulum oscillate at a measurable frequency; a quartz clock uses electricity to make a quartz crystal oscillate at a measurable frequency; an atomic clock uses microwaves to make caesium (or similar) atoms oscillate at a measurable frequency. In the 1970s, the only way to synchronise your atomic clock with the one at the International Bureau of Weights and Measures was to take it to Paris with you and compare them side by side. Now it’s all done by satellite signals. GPS time is also what enables stocks and shares to change hands in microseconds, prevents power surges in vast electrical grids and keeps the internet ticking smoothly.
But before it was co-opted as the pocketwatch of late capitalism – a gift from the US government – GPS was developed as a way to help the US air force drop its bombs just where it wanted with as little risk as possible to American lives. As with any technological breakthrough, it took decades, with false starts, moments of inspiration, patient refinements, scepticism from the brass (‘We’re the navy, we know where we are’), inter-service rivalry and a more or less steady influx of government cash. Within days of Sputnik’s launch in 1957, two young engineers at Johns Hopkins University were using the Russian satellite’s radio signal to plot and then predict its position. GPS came of age in the 1991 Gulf War. (...)
There used to be two different GPS signals: a high-precision one, which only military receivers could decrypt, and a deliberately degraded one for civilian use, which gave your position to within a hundred metres or so. When US troops started shipping out to the Gulf after Saddam Hussein invaded Kuwait in August 1990, they had only 13 Manpack portable GPS receivers between them. Each one cost $40,000 and weighed 12 kg. The Department of Defence put in an order for thousands of Trimpacks, portable receivers built by a former Hewlett Packard engineer called Charlie Trimble (one of the many people Milner interviewed). But there still weren’t enough to go round, so a lot of soldiers ended up spending $1000 of their own money on mass-produced Magellan portable receivers, which were less accurate than Trimpacks but better than nothing in the middle of a hostile desert. The Magellans were made by Ed Tuck, an ex-military venture capitalist with a background in the tech industry. He’d imagined selling cheap (less than $300) GPS receivers to middle-aged men who didn’t like admitting they were lost or asking for directions, but many of his early customers were people with boats off the southern coast of Florida – drug dealers or people traffickers.
Because so many soldiers in Desert Storm were carrying GPS receivers that used the civilian signal, the military turned off the ‘selective availability’ software that degraded it. They turned it on again when the Gulf War was over, but amateur GPS enthusiasts would have noticed a sudden improvement in their receivers’ accuracy in September 1994, when US forces landed on Haiti to depose General Cédras and restore Jean-Bertrand Aristide to power. Meanwhile, commercial GPS receiver manufacturers were developing ways to overcome or work around selective availability, and make their products more accurate in spite of it. In May 2000 the military stopped degrading the civilian GPS signal. Sales of GPS receivers soared.
It isn’t just every phone and every Uber car that’s now fitted with GPS; in some parts of the world it’s every tractor too. And not because farmers need to be reminded of the way to their fields. Milner visited a sugar beet farm in Colorado, a few hours north of Schriever Air Force Base. Using GPS in combination with the Russian GLONASS system to achieve ‘sub-inch accuracy’, the beet farmer tills his field in strips, leaving a narrow band of fallow earth between each row to help keep water and nutrients in the soil. Each seed is planted in a precise, recorded position, with more of them in the more fertile parts of the field. Just the right amount of water and fertiliser is sprayed onto the beets. When they’re harvested, each and every one can be plucked entire from the earth (a broken beet is no use to anyone). Milner reckons that GPS is now worth billions a year to American farmers. An experiment in Uttar Pradesh, meanwhile, found that levelling the land on a two-acre farm using GPS nearly tripled the wheat yield. The farmer in Colorado told Milner that GPS gives him ‘intimate knowledge’ of the land, like his grandfather, who walked behind a horse looking at the ground beneath his feet. Still, hi-tech agriculture has its downsides. Not so many years ago, it took two men to harvest a beet field: one of them driving the tractor, the other operating the digger at the back. Now the tractor does almost everything itself; the driver merely has to turn it round at the end of the row. Soon, he won’t have to do even that. A former farmhand in East Yorkshire told me this summer that he had stopped driving tractors because he can’t understand the computers.
Greg Milner includes a few stories about satnav fails in Pinpoint, his lively history of satellite navigation technology – his central chapter is called ‘Death by GPS’ – but one of the eye-opening things about his book is quite how far-reaching the tech is. As well as guiding missiles and encouraging motorists not to pay attention to road signs or even to the road ahead of them, GPS is used in crop management, high frequency trading, weather forecasting, earthquake measurement, nuclear-detonation detection and space exploration, as well as the smooth running of countless infrastructure networks, from electricity grids to the internet.
GPS, which stands for Global Positioning System, was developed by the American military. The US Department of Defence currently spends more than a billion dollars a year maintaining it. There are 31 GPS satellites orbiting the earth, all monitored, along with hundreds of other military satellites, from Schriever Air Force Base in Colorado. For the system to work, a receiver on the ground – your mobile phone, for example – needs to have a ‘line of sight’ to at least four of the satellites (there are very few places on earth where it wouldn’t). Each satellite continously broadcasts its position, along with the time the signal left the satellite. The time it takes for the signal to reach you (measured in milliseconds) will tell you exactly how far away it is. Three of these signals provide enough information to pinpoint your position; the fourth confirms the time used in the calculations. GPS satellites, unlike mobile phones, carry super-accurate atomic clocks, which are continually synchronised with one another. This is necessary for the precision of the positioning system, but many of the applications of GPS make use of it primarily as a timekeeping device.Since 1967, the second has been defined as ‘the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom’. A pendulum clock uses gravity to make a pendulum oscillate at a measurable frequency; a quartz clock uses electricity to make a quartz crystal oscillate at a measurable frequency; an atomic clock uses microwaves to make caesium (or similar) atoms oscillate at a measurable frequency. In the 1970s, the only way to synchronise your atomic clock with the one at the International Bureau of Weights and Measures was to take it to Paris with you and compare them side by side. Now it’s all done by satellite signals. GPS time is also what enables stocks and shares to change hands in microseconds, prevents power surges in vast electrical grids and keeps the internet ticking smoothly.
But before it was co-opted as the pocketwatch of late capitalism – a gift from the US government – GPS was developed as a way to help the US air force drop its bombs just where it wanted with as little risk as possible to American lives. As with any technological breakthrough, it took decades, with false starts, moments of inspiration, patient refinements, scepticism from the brass (‘We’re the navy, we know where we are’), inter-service rivalry and a more or less steady influx of government cash. Within days of Sputnik’s launch in 1957, two young engineers at Johns Hopkins University were using the Russian satellite’s radio signal to plot and then predict its position. GPS came of age in the 1991 Gulf War. (...)
There used to be two different GPS signals: a high-precision one, which only military receivers could decrypt, and a deliberately degraded one for civilian use, which gave your position to within a hundred metres or so. When US troops started shipping out to the Gulf after Saddam Hussein invaded Kuwait in August 1990, they had only 13 Manpack portable GPS receivers between them. Each one cost $40,000 and weighed 12 kg. The Department of Defence put in an order for thousands of Trimpacks, portable receivers built by a former Hewlett Packard engineer called Charlie Trimble (one of the many people Milner interviewed). But there still weren’t enough to go round, so a lot of soldiers ended up spending $1000 of their own money on mass-produced Magellan portable receivers, which were less accurate than Trimpacks but better than nothing in the middle of a hostile desert. The Magellans were made by Ed Tuck, an ex-military venture capitalist with a background in the tech industry. He’d imagined selling cheap (less than $300) GPS receivers to middle-aged men who didn’t like admitting they were lost or asking for directions, but many of his early customers were people with boats off the southern coast of Florida – drug dealers or people traffickers.
Because so many soldiers in Desert Storm were carrying GPS receivers that used the civilian signal, the military turned off the ‘selective availability’ software that degraded it. They turned it on again when the Gulf War was over, but amateur GPS enthusiasts would have noticed a sudden improvement in their receivers’ accuracy in September 1994, when US forces landed on Haiti to depose General Cédras and restore Jean-Bertrand Aristide to power. Meanwhile, commercial GPS receiver manufacturers were developing ways to overcome or work around selective availability, and make their products more accurate in spite of it. In May 2000 the military stopped degrading the civilian GPS signal. Sales of GPS receivers soared.
It isn’t just every phone and every Uber car that’s now fitted with GPS; in some parts of the world it’s every tractor too. And not because farmers need to be reminded of the way to their fields. Milner visited a sugar beet farm in Colorado, a few hours north of Schriever Air Force Base. Using GPS in combination with the Russian GLONASS system to achieve ‘sub-inch accuracy’, the beet farmer tills his field in strips, leaving a narrow band of fallow earth between each row to help keep water and nutrients in the soil. Each seed is planted in a precise, recorded position, with more of them in the more fertile parts of the field. Just the right amount of water and fertiliser is sprayed onto the beets. When they’re harvested, each and every one can be plucked entire from the earth (a broken beet is no use to anyone). Milner reckons that GPS is now worth billions a year to American farmers. An experiment in Uttar Pradesh, meanwhile, found that levelling the land on a two-acre farm using GPS nearly tripled the wheat yield. The farmer in Colorado told Milner that GPS gives him ‘intimate knowledge’ of the land, like his grandfather, who walked behind a horse looking at the ground beneath his feet. Still, hi-tech agriculture has its downsides. Not so many years ago, it took two men to harvest a beet field: one of them driving the tractor, the other operating the digger at the back. Now the tractor does almost everything itself; the driver merely has to turn it round at the end of the row. Soon, he won’t have to do even that. A former farmhand in East Yorkshire told me this summer that he had stopped driving tractors because he can’t understand the computers.
by Thomas Jones, LRB | Read more:
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[ed. I had a project that used some of the earliest commercial versions of GPS technology (around 1992) to map salmon streams in remote Alaskan back-country, then feed those locations in ArcInfo for mapping. Selective availability was a bitch and overcoming it required triangulation from several locations, some of which entailed a lot of frustrating bushwhacking to get to sites high enough on mountain sides to get good, reliable Sat signals. A lot of extra effort to overcome Defense Dept. paranoia.]
[ed. I had a project that used some of the earliest commercial versions of GPS technology (around 1992) to map salmon streams in remote Alaskan back-country, then feed those locations in ArcInfo for mapping. Selective availability was a bitch and overcoming it required triangulation from several locations, some of which entailed a lot of frustrating bushwhacking to get to sites high enough on mountain sides to get good, reliable Sat signals. A lot of extra effort to overcome Defense Dept. paranoia.]
