Last Updated on August 8, 2026 by Karl Thompson
This article is about time rather than maps. It argues that the most important thing satellite navigation gives modern Britain is not the blue dot on a phone screen but a single, shared, extraordinarily precise definition of now — and that every society which has needed shared time has had to decide who supplies it. Ours has answered that question in a way most people have never been asked about.
This is part of How Modern Society Works, a series on the hidden systems that shape everyday life. Each article takes something ordinary and works outwards to the system that produced it.
An Ambulance Is Dispatched
Someone collapses in a supermarket car park. A stranger dials 999 from a mobile phone.
Twenty years ago, what happened next depended on that stranger’s ability to describe where they were standing. Call handlers spent minutes establishing a location, sometimes from people too frightened to think clearly, often in places without a memorable address. The clock ran while they talked.
Today, on most smartphones, the handset transmits its own position to the emergency call centre automatically, using satellite signals to place the caller within tens of metres rather than the thousands of metres a mobile mast could manage. The handler confirms rather than interrogates. The ambulance is given a destination rather than a description.
The UK government has put a value on that difference. A study commissioned by the UK Space Agency estimates the annual benefit of satellite-derived caller location to the emergency services at £5.4 billion — the single largest identified benefit of satellite navigation anywhere in the British economy, larger than road navigation, larger than agriculture, larger than shipping.
That figure ought to be surprising. Satellite navigation is usually discussed as a convenience: a way of avoiding the M25, or of watching a curry approach on a map. Its largest measured contribution to British life is shortening the interval between a stranger’s phone call and a paramedic’s arrival.
It is worth holding onto that, because most of this article is about power, ownership and surveillance, and it would be easy to lose sight of the ambulance.
How Does GPS Calculate Your Position?
The Global Positioning System has three parts, and only one of them is in space.
Roughly thirty satellites orbit around 20,200 kilometres above the Earth, high enough that each is visible from an enormous portion of the planet’s surface. A network of ground stations tracks them, corrects their orbital models and uploads updated data. And several billion receivers — in phones, cars, ships, tractors, aircraft, shipping containers and ankle tags — listen.
Each satellite broadcasts two things continuously: where it is, and precisely when the signal left. Because radio waves travel at a known speed, a receiver that knows both can calculate how far away the satellite is. One satellite places you somewhere on the surface of an enormous sphere. Two narrow it to a circle. Three narrow it to two points, one of which is usually absurd. Four resolve the position and, crucially, correct the receiver’s own cheap and inaccurate clock. The technique is called trilateration.
Everything therefore rests on timing, and the tolerances are unforgiving. An error of one microsecond — one millionth of a second — moves your calculated position roughly 300 metres. This is why every GPS satellite carries atomic clocks, and why the ground segment spends its life making tiny corrections to them.
The consequence is easy to miss and central to everything that follows. A GPS receiver does not really measure distance. It measures time, and infers distance. Every position fix is a timing calculation wearing a map.
Strictly, GPS is one of four such systems. Alongside the American constellation sit Europe’s Galileo, Russia’s GLONASS and China’s BeiDou, together known as Global Navigation Satellite Systems, or GNSS. Most modern phones listen to several at once. Why four systems exist where one would do is a question we will come back to, because the answer is not technical.
A Short History of Shared Time
Here is a question that sounds trivial and is not: how did people know when to turn up?
For most of human history, they didn’t, at least not in the sense we mean. Time was local and it was approximate. Dawn, noon, dusk. Market day. The interval it takes to boil a pot. Communities coordinated through events they could all observe.
Émile Durkheim, writing in 1912, argued that time itself is a social institution rather than a private intuition. The calendar, he pointed out, does not track anything in individual experience; it tracks the rhythm of collective activity — festivals, rites, markets, assemblies. A shared sense of time is not a convenience that societies happen to adopt. It is one of the things that makes a society a society rather than a crowd.
If Durkheim explains why shared time exists, the historian E. P. Thompson explained what happens when someone owns it. In his 1967 essay Time, Work-Discipline and Industrial Capitalism, Thompson traced the shift from task-oriented work — you work until the job is done — to clock-oriented work, in which employers purchase measured intervals of a worker’s life. The factory clock was not a neutral instrument. Workers noticed that it seemed to run slowly in the afternoon. Some employers locked it in a case.
The pattern has repeated with every enlargement of the scale at which societies coordinate. Monasteries had bells. Towns had church clocks. Then, in the nineteenth century, the railways arrived and local time became impossible: a train that leaves Bristol at ten and arrives in London at noon needs Bristol and London to agree on what those words mean. Railway companies imposed a single national standard, and Britain’s towns gave up their own noon, not always graciously. Greenwich Mean Time was a commercial necessity before it was a national institution.
Each step follows the same logic. As the radius of coordination expands, so does the scale of the clock required — and each new clock has an owner.
Which brings us to the present arrangement. The world now coordinates continuously and globally, and the clock that permits it is a constellation of atomic oscillators in medium Earth orbit, maintained by the armed forces of the United States.
Nobody proposed this. There was no moment at which anyone decided that the successor to the parish church bell would be the US Space Force. It happened the way infrastructure usually happens: incrementally, for local reasons, until the arrangement was too embedded to revisit.
What Would Happen If GPS Stopped Working?
If satellite timing were switched off tomorrow, what would actually break?
This turns out to be a question with a researched answer, and the answer contains a genuine surprise.
The London Economics assessment for the UK Space Agency modelled a complete seven-day GNSS outage across the UK. Total economic loss: £7.64 billion. A twenty-four hour outage: £1.42 billion. Those are large numbers, but the distribution is more interesting than the total. Three sectors — emergency services, maritime and road transport — account for 87.6% of the entire loss.
The surprise is what is absent from that list.
Financial markets are the example everyone reaches for when explaining why precise timing matters, and there is a real regulatory requirement behind the instinct: European rules oblige trading venues to timestamp transactions against a common reference with defined accuracy. Yet the study found that stock exchanges and high-frequency trading firms maintain sophisticated oscillators capable of holding accurate time long after the external signal disappears, and concluded there would be no economic loss in the finance sector across a seven-day outage. Fixed and cellular telecommunications networks reached the same verdict: sufficient holdover to ride out the week without functional impact.
The institutions with the most to lose from a timing failure have quietly bought their way out of the dependency. Everyone else has not.
So the losses fall elsewhere. Ports stop, because automated cranes cannot position containers and there is no fallback: maritime losses over seven days run to £1.5 billion, with port operations alone at £1.3 billion. Roads clog, because turn-by-turn navigation vanishes for millions of drivers simultaneously and journey times lengthen for everyone, including those who never used it. And the emergency services absorb the largest loss of all — £3.5 billion — as caller location degrades to cell-tower accuracy, calls take longer, and a proportion of them fail to reach an operator at all.
The pattern is worth naming, because it recurs throughout this book. Resilience is a purchased good. Organisations wealthy enough to hold their own atomic clocks are insulated; a public service under permanent budget pressure is not. Vulnerability to infrastructure failure is not distributed randomly. It settles, like most things, along existing lines of resource.
Agriculture supplies a quieter variant. Satellite guidance lets a tractor reduce the overlap between successive passes across a field from around thirty centimetres to about four, saving fuel, seed and fertiliser. But the researchers made an assumption worth pausing on: a farmer who has relied on the system for a decade could no longer achieve even the old thirty-centimetre standard by eye, and they doubled the estimated loss accordingly.
This is the ratchet that infrastructure creates. A system that begins by supporting a skill ends by replacing it. The capability does not sit alongside the human competence; it absorbs it, and the competence quietly leaves the population. There is no going back to the previous arrangement, because the previous arrangement lived in people who have retired.
Who Owns and Controls GPS?
GPS is owned by the United States government, operated by the US Space Force, and supplied free of charge to the entire world.
That last clause has done remarkable work. Free access made GPS the global default, and the global default became load-bearing for the economies of countries with no say whatever in its operation. Britain’s ports, ambulances and farms depend on a military asset belonging to a foreign state.
For a long time this troubled almost nobody, which is itself instructive. Infrastructure dependence tends to become visible only when the relationship it rests on comes into doubt.
Europe’s response was Galileo, deliberately built under civilian control, and justified in the language of strategic autonomy rather than accuracy: the argument was less that GPS was insufficient than that depending on it was a political condition rather than a technical one. China built BeiDou. Russia maintains GLONASS. Four constellations now do a job that one constellation does perfectly well, which tells you the redundancy is not primarily engineering redundancy. It is sovereignty, expressed in orbit.
There is a sharper illustration in Britain’s own recent experience. On leaving the European Union, the UK lost access to the safety-critical tier of the European augmentation service that improves satellite positioning for aircraft. The consequence was concrete: a number of British runways lost the ability to offer their more precise satellite-guided approach and reverted to older ground-based instrument landings, with correspondingly tighter limits in poor weather.
That is worth sitting with. A political decision taken for reasons entirely unrelated to aviation changed the conditions under which aircraft may land at British airports in fog. Infrastructure dependence means that political events arrive in places nobody expected them.
Who Gets Located
So far this article has treated positioning as something we do. It is also, increasingly, something done to people.
The same technology that tells you where you are tells other parties where you are, and the question of which is happening depends entirely on who holds the receiver and who reads the output.
Consider electronic monitoring. Satellite location tags were introduced into the criminal justice system of England and Wales in November 2018. By March 2026, location tags accounted for 57% of everyone fitted with an electronic monitoring device — 16,264 individuals — and the National Audit Office reported the monitored population had roughly doubled over five years, with substantial further expansion planned as an answer to prison overcrowding. A tag creates exclusion zones, attendance requirements and a continuous positional record. It is, quite precisely, a prison whose walls are defined in coordinates rather than brick, and it exists because satellite positioning made that form of confinement possible and cheap.
Consider motor insurance. Telematics — a device or app that reports how, when and where a policyholder drives — was a marginal product in 2017. In the updated UK assessment its estimated annual benefit had risen by more than 8,000%, to £1.32 billion, making it one of the largest single satellite-navigation applications in the country. The benefit is real, and it accrues asymmetrically: insurers gain information they previously could not obtain, and drivers gain lower premiums in exchange for continuous observation. Young drivers, who often cannot obtain affordable cover otherwise, are least able to decline the trade.
Consider work. Fleet management, route optimisation, delivery tracking and driver monitoring all rest on the same signal. The delivery driver whose van reports its position every few seconds is inside a system Thompson would have recognised instantly: the measurement of the working interval, refined to the point where the employer knows not merely that you were late but where you slowed down.
And then there is the story that draws all of this together, from a French court file.
In April 2017, flights at Nantes Atlantique airport were delayed when aircraft tracking systems suffered severe interference. The source was eventually located by police in the airport car park: a motorist had parked with a GPS jamming device still running in his vehicle. Such devices are illegal in France, as in Britain, and are used by some drivers for a specific purpose — to stop their vehicle being tracked by their employer.
One man’s attempt to escape workplace surveillance disrupted an international airport.
It is a small incident and it contains most of this article. The same infrastructure that dispatches ambulances tracks employees. The person resisting it had no way to resist it locally, because the signal is not local. And the fragility of the whole arrangement was demonstrated by a device costing a few tens of pounds, sitting in a car park.
What Is GPS Jamming and Spoofing?
By the time a GPS signal reaches the Earth’s surface it is extraordinarily weak — it has travelled more than twenty thousand kilometres, and the power arriving at your phone is a tiny fraction of ordinary background radio noise. Receivers extract it through clever signal processing rather than brute strength. This makes the system remarkably easy to overwhelm.
Jamming broadcasts noise on the same frequencies, and receivers simply stop producing a fix. Spoofing is more sophisticated and considerably more dangerous: rather than blocking the signal, it transmits counterfeit signals, and receivers calculate a confident, precise and entirely false position. A ship’s crew watching their own vessel appear several kilometres from its actual location has no immediate way of knowing which reading to disbelieve.
Both have moved from theoretical vulnerability to routine condition. Interference affecting civil aviation has risen sharply since February 2022, concentrated around conflict zones — the Baltic, the Black Sea, the eastern Mediterranean, the Middle East — and by mid-2025 European aviation regulators and the airline industry had shifted their stated posture from containing the problem to living with it, publishing a joint mitigation plan built around information-sharing, airspace management and preparedness rather than prevention.
Aircraft have not been falling out of the sky, and it is important not to overstate this. Commercial aviation retains inertial navigation and ground-based systems precisely because it never assumed satellite positioning would always be available. Aviation, like finance, bought its resilience in advance.
The concern is what happens in the sectors that didn’t. The UK study modelled a jamming incident at the Port of Dover, which handles an average of £334 million of goods each day, and found that a single day’s disruption could stack more than 850 lorries into a queue over ten kilometres long. Space weather offers the same threat without an author: a sufficiently large solar event could degrade all four constellations at once, and researchers estimate a roughly 4% annual probability of a great solar storm.
Time, Power and the Ambulance
Every society that coordinates at scale needs a shared clock, and every shared clock has an owner. Monasteries owned bells. Employers owned the factory clock and occasionally locked it in a case. Railway companies imposed the national standard because their timetables demanded it. In each case, the people who supplied the time acquired an authority that was not obviously about time at all.
We have simply continued the sequence, at planetary scale, with an owner most people could not name. The shared clock is now a constellation of atomic oscillators operated by a foreign military, distributing a common definition of now to several billion devices for free, and modern Britain has organised its ports, its farms, its roads, its courts and its ambulance dispatch around the assumption that it will continue to do so.
This is not a lament. The ambulance arrives faster, and £5.4 billion a year of that improvement is measurable. The point is narrower and, I think, harder: a society can restructure itself around an external clock without ever holding a discussion about it, and the restructuring is complete before the question is asked.
What that restructuring has produced is not a single dependency but an unevenly distributed one. Exchanges and airlines hold their own time and can survive without the signal. Ports, ambulances and drivers cannot. The people most exposed to a satellite timing failure are, with dispiriting predictability, the ones already least able to buy their way out of it. And a growing number of people experience satellite positioning not as a service they use but as a condition imposed on them — tagged, monitored, priced by observation.
This completes a pattern the series has been assembling. Data centres showed infrastructure competing for finite land and power, with the contest settled by a connection queue. Fibre showed it allocated by expected return, and then devalued when the return failed to arrive. Cloud computing showed institutions trading ownership for access, and discovering that access comes with terms. Payment networks showed the same trade made in the currency of trust. Each chapter asked who owns a system that everybody uses, and each got a version of the same answer: somebody else, somewhere else, on terms nobody here negotiated.
Satellite timing completes it because time is the most basic coordinating resource of all, and because the arrangement is the most extreme. Britain does not merely rent its computing and finance its cables with foreign capital. It takes its definition of now from a foreign military, for free, and has built its ambulance dispatch, its ports and its farms around the assumption that this will continue.
Infrastructure is often described as neutral. This one is a clock, and clocks have never been neutral. They tell you what time it is, and they tell you whose time it is.
References
| Claim | Source | URL | Why it supports the claim |
|---|---|---|---|
| Emergency-services caller location worth £5.43bn/year; GNSS total annual UK benefit £13.6bn | London Economics for the UK Space Agency, The economic impact on the UK of a disruption to GNSS, final report, 2023 | https://assets.publishing.service.gov.uk/media/652eb0446b6fbf000db7584e/20231018_London_Economics_Report_GNSS.pdf | Executive Summary and Table 11 give the annual benefit figures by sector |
| Seven-day outage loss £7.64bn; 24-hour loss £1.42bn | as above | as above | Executive Summary, key findings |
| Emergency services, maritime and road = 87.6% of seven-day loss | as above | as above | Executive Summary |
| Finance and telecoms have sufficient holdover; no seven-day loss | as above | as above | Finance section and Table 4; telecoms in Table 8 |
| Maritime seven-day loss £1.5bn, of which port operations £1.31bn | as above | as above | Table 6, maritime applications |
| Tractor pass-to-pass overlap reduced from 30cm to 4cm; deskilling assumption doubles estimated loss | as above | as above | §4.1.1, economic loss discussion |
| Insurance telematics annual benefit £1,323.8m, up 8,122% since 2017 | as above | as above | Table 7, road applications |
| Nantes Atlantique airport jamming incident, April 2017, motorist evading employer tracking | as above | as above | §2.2, loss of GNSS case studies |
| Port of Dover: £334m of commodities per day; 850 lorries, 10km queue in a jamming scenario | as above | as above | §5, Less-than-Worst-Case Scenario 1 |
| Loss of EGNOS Safety of Life service after EU exit removed precision approaches from around 25 UK runways | as above | as above | §4.2.1, scope of aviation sector |
| Roughly 4% annual probability of a great solar storm | as above | as above | §2.3.4, citing Chapman, Horne and Watkins (2020) |
| Satellite location tags introduced November 2018; RF tags from 1999 | Ministry of Justice, Electronic Monitoring Statistics technical note | https://www.gov.uk/government/statistics/electronic-monitoring-statistics-publication-september-2023/technical-note | States the introduction dates for both tag types |
| 16,264 individuals on location (GPS) tags, 57% of all those monitored, March 2026 | Ministry of Justice, Electronic Monitoring Statistics Publication, England and Wales: March 2026 | https://www.gov.uk/government/statistics/electronic-monitoring-statistics-publication-march-2026/electronic-monitoring-statistics-publication-england-and-wales-march-2026 | Figure 2 and accompanying commentary |
| Rising GNSS interference since Feb 2022; regulators shift from containment to resilience, June 2025 | European Union Aviation Safety Agency press release, 18 June 2025 | https://www.easa.europa.eu/newsroom-and-events/press-releases/easa-and-iata-outline-comprehensive-plan-mitigate-gnss | Announces the joint EASA–IATA mitigation plan and its four areas |
| GPS ownership, constellation, three segments, free civil service | GPS.gov, US government official site | https://www.gps.gov/systems/gps/ | Official description of space, control and user segments |
| Galileo under civilian control; multi-constellation receivers now standard | EUSPA, What is GNSS? | https://www.euspa.europa.eu/eu-space-programme/galileo/what-gnss | Describes the four constellations and civilian governance of Galileo |
Classic reading
- Émile Durkheim, The Elementary Forms of Religious Life (1912) — the categories of understanding, including time, as collective representations: “a calendar expresses the rhythm of collective activity at the same time that it functions to ensure its regularity”
- E. P. Thompson, ‘Time, Work-Discipline and Industrial Capitalism’, Past and Present 38 (1967), pp. 56–97
- Eviatar Zerubavel, Hidden Rhythms: Schedules and Calendars in Social Life (1981)
- Michel Foucault, Discipline and Punish (1975) — on monitoring, the timetable and dispersed confinement
How Modern Society Works
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