Satellite navigation systems keep our world going in ways that many people barely recognize, but they are also increasingly fragile. What could we use instead?
When satellite navigation was blocked at Israel's Ben Gurion Airport last year, only the skills of the air traffic controllers prevented serious accidents. The disturbance was apparently accidental and originated in the Russian forces fighting in Syria. However, it showed how dangerous disruptions to the global positioning system - better known as GPS - can be.
"There is growing recognition that GPS needs to be protected, tightened, and expanded," said Todd Humphreys, communications engineer at the University of Texas at Austin. GPS now underpins a surprising part of our everyday life. In its simplest form, it tells us where on earth a GPS receiver is at any given time. We have them in our cell phones and cars. They allow boats to move through difficult channels and reefs like a modern lighthouse. Emergency services now rely on GPS to locate those in need.
Less obviously, ports would no longer work as their cranes need GPS to find the right container to move, and they play a vital role in logistics so that automakers and supermarkets can use just-in-time delivery systems. Without them, our supermarket shelves would be emptier and prices would be higher.
The construction industry uses GPS for surveying and fishermen use it to comply with strict regulations. However, GPS is not just about identifying locations, it's also about time.
The constellation of 30 satellites in orbit around the earth uses several extremely precise atomic clocks to synchronize their signals. With them, users can pinpoint the time to within 100 billionths of a second. Cellular networks all use GPS time to synchronize their base stations, while financial and banking institutions rely on it to make sure trades and transfers are correct.
Without satellite navigation we would really be lost. But is there anything out there that could replace it? And how could we do without this ubiquitous system?
Loss of satellite navigation for five days would cost the UK alone more than GBP 5.1 billion (USD 6.5 billion), according to an estimate by the London School of Economics. A failure of the GPS system would also cost the US economy an estimated $ 1 billion (£ 760 million) per day and up to $ 1.5 billion (£ 1.1 billion) per day if it did so during the The planting season for farmers would be April and May.
But GPS failures are surprisingly common - the military regularly blocks them in certain areas while testing equipment or performing military exercises. The US government also regularly conducts tests and exercises that result in interference with the satellite signal, but some technical issues also create global problems.
There are of course other global navigation satellite systems - the Russian Glonass, the European Galileo and the Chinese BeiDou all work on a similar basis to GPS. Increasingly, interference or deliberate interference can also lead to interruptions in the signals from satellite positioning systems.
"The military is running into disruption quite a bit now," said Charley Curry, Fellow of the Royal Institute of Navigation and founder of Chronos Technology, which works in the field.
The military has particularly good reasons to be concerned. Satellite navigation was originally developed by the Pentagon and now carries everything from strategic drones and warships to individual intelligent bombs and foot soldiers. And it's in danger.
Criminals also use GPS jammer, which can easily be bought online, to track the systems that track stolen cars without worrying about who else is affected in the area. And there are greater dangers.
