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global positioning system

Navsop, a new positioning system made by UK defence firm BAE Systems, has been developed to complement or even replace current technologies such as GPS.

Navsop relies on the same signals used by mobile phones, TVs, radios and wi-fi rather than navigation satellites.

BAE Systems says Navsop could help find victims inside buildings during a fire and locate stolen vehicles hidden in underground car parks.

It could also be used in a war if the sat-nav system was turned off.

For now, the prototype is a big box-like piece of hardware placed in the back of one of BAE’s cars, which sports a radio antenna on the roof.

But once out on the market, it will be as tiny as a GPS dongle is today – a bit bigger than a coin – says Ramsey Faragher, principal scientist at the BAE Advanced Technology Centre in Chelmsford, near London.

“Let’s be clear – for Navsop to start working, you have to have a GPS signal, to know where you are on the face of the Earth,” he says, sitting in the back of the car as it drives along Chelmsford’s streets.

“But if the GPS signal disappears, we’ll still be able to navigate,” he adds, pointing to the computer screen depicting a map with a dotted line showing the vehicle’s location.

Navsop relies on the same signals used by mobile phones, TVs, radios and wi-fi rather than navigation satellites

Navsop relies on the same signals used by mobile phones, TVs, radios and wi-fi rather than navigation satellites

The device works by picking up all the available signals nearby, heavily relying on medium wave radio frequencies.

This is the same part of the spectrum used by radio pioneer Guglielmo Marconi more than a 100 years ago, who opened the world’s first telegraph in the same city.

GPS (global positioning system) uses signals coming from satellites spinning around the Earth, some 20,000 km (12,427 miles) away.

By the time these signals reach the surface of our planet, they are extremely weak and unable to be picked up by receivers, for instance, inside buildings.

They may also suddenly disappear, says Ramsey Faragher.

“Our society has now become hugely dependent on GPS,” he adds.

“The European Commission determined that 800bn euros [$995bn; £642bn] of the European economy is dependent on either precision navigation or precision timing from GPS – the aviation industry, the shipping industry, agriculture, telecommunications, all need GPS to function.

“And that’s why it’s important to have back-up systems in case GPS signal is not available.”

For instance, there have been cases when criminals have stolen cars and used GPS jammers bought over the internet to prevent the vehicles’ owners from trying to locate them.

There are also natural space events such as solar flares that result in a release of a very large cloud of charged particles, which, once they hit the Earth’s atmosphere, can prevent GPS signals from coming through cleanly.

But mobile phones, radios and TVs use signals that are a lot more powerful than those from navigation satellites, as they are broadcast from only a few kilometres away, and cannot be jammed.

So Navsop uses them instead.

“We are not saying that our technology should necessarily replace GPS, but rather complement it,” says Ramsey Faragher.

“If the GPS signal is there, by all means, use it. If not, we say that with Navsop, you can determine your position anyway.”

And this could be useful in a variety of scenarios – from precisely determining the position of trains in tunnels to locating victims trapped in buildings after explosions or earthquakes.

It would also be useful to the military in case one side deliberately switches off GPS to prevent its adversary from locating its units.

BAE Systems says that for now, it is not clear when the technology will be put on the market, but in principle it could be used by countries developing other sat-nav technologies.

Currently, Russia has Glonass, and China is building Beidou, also known as Compass.

The European Union and European Space Agency are developing Galileo, a separate 20 billion-euro project.


Scientists claim that spacecrafts could one day navigate through the cosmos using a particular type of dead star as a kind of GPS.

German scientists are developing a technique that allows for very precise positioning anywhere in space by picking up X-ray signals from pulsars.

These dense, burnt-out stars rotate rapidly, sweeping their emission across the cosmos at rates that are so stable they rival atomic clock performance.

This timing property is perfect for interstellar navigation, says the team.

If a spacecraft carried the means to detect the pulses, it could compare their arrival times with those predicted at a reference location. This would enable the craft to determine its position to an accuracy of just five kilometres anywhere in the galaxy.

“The principle is so simple that it will definitely have applications,” said Prof. Werner Becker from the Max-Planck Institute for Extraterrestrial Physics in Garching.

“These pulsars are everywhere in the Universe and their flashing is so predictable that it makes such an approach really straightforward,” said Prof. Werner Becker.

Spacecrafts could one day navigate through the cosmos using a particular type of dead star as a kind of GPS

Spacecrafts could one day navigate through the cosmos using a particular type of dead star as a kind of GPS

Prof. Werner Becker has been describing his team’s research here at the UK National Astronomy Meeting in Manchester.

The proposed technique is very similar to that employed in the popular Global Positioning System, which broadcasts timing signals to the user from a constellation of satellites in orbit.

But GPS only works on, or just above, the Earth so it has no use beyond our planet.

Currently, mission controllers wanting to work out the position of their spacecraft deep in the Solar System will study the differences in time radio communications take to travel to and from the satellite. It is a complex process and requires several antennas dotted across the Earth.

It is also a technique that is far from precise, and the errors increase the further away the probe moves.

For the most distant spacecraft still in operation – NASA’s Voyager satellites, which are now approaching the very edge of the Solar System, some 18 billion km away – the errors associated with their positions are on the order of several hundred kilometers.

Even for a probe at the reasonably short separation of Mars, the positioning uncertainty can be about 10 km.

It is unlikely though that navigation by pulsar beacon will find immediate use.

The telescope hardware for detecting X-rays in space has traditionally been bulky and heavy.

Engineers will need to miniaturize the technology to make a practical pulsar navigation unit.

“It becomes possible with the development of lightweight X-ray mirrors,” said Prof. Werner Becker.

“These are on the way for the next generation of X-ray telescopes. Current mirrors have a 100 times more weight and would be completely unusable.

“In 15-20 years, the new mirrors will be standard and our device will be ready to be built.”

The scientist believes his navigation solution will certainly find use on Solar System probes, providing autonomous navigation for interplanetary missions and perhaps for future manned ventures to Mars where high performance systems will be an absolute requirement for safety reasons.

But he also likes the idea of humanity one day pushing out across interstellar space.

“You know for GPS that if you go to another country, you have to buy the maps for your device. Well, we were joking with our students in Garching about selling maps for different galaxies for ships like Enterprise [on Star Trek].”