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The next-generation of deep-space GPS satellites has just reached a milestone -- but an even better, unjammable system is already available here on earth.

Last week Lockheed Martin crossed a milestone, finishing "thermal vacuum" tests for GPS III, a new class of satellites that will replace the aging craft in orbit around Earth. GPS III will introduce anti-jamming tech to address a serious threat to troops, drones and ships that rely on GPS for navigation and targeting.

The first satellite could launch in 2014, but a better option may already exist: BAE's Navigation via Signals of Opportunity (NAVSOP) doesn’t depend on satellite signals, instead using a wide range of common signals readily available to sidestep jammers.

It can even use the GPS jammer signal itself. And it’s just as accurate, BAE says.

In BAE’s system, everyday signals like TV, Wi-Fi, radio or cell phone are used to triangulate the location of a person or vehicle. NAVSOP gets the position exact within several feet with this signal-scavenging approach.

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It uses all sorts of other signals as well, from GPS satellite to air traffic control. The system can even learn and evolve by taking signals that were originally unidentified and using them to build increasingly reliable and more exact fixes on location.

Shifting to the cheap and nimble NAVSOP would not require infrastructure investments in transmitter towers and the like, because it takes advantage of whatever is already in place.

Larger models are in development, but NAVSOP chips are approximately the size of a coin and work with a tiny radio receiver.

From the Arctic to the Jungle

Harvesting signals from the air allows NAVSOP to work in places where GPS has traditionally failed, because receivers struggle to pick up the weak, long-range satellite signals.

GPS signals travel over approximately 12,000 miles, so by exploiting stronger signals transmitted from Earth, NAVSOP will work deep underground, underwater, in tunnels or inside buildings. For warfighters, NAVSOP can also work in remote locations such as the deep jungle or the Arctic.

Military applications for NAVSOP are wide. Take Iran’s recent claim that the country took control of a U.S. Sentinel drone. Unmanned Aerial Vehicles (UAVs) face the threat of disruption to their guidance systems; NAVSOP would greatly improve their security.

But this technology could do much more than just harden military weapons and vehicles against enemy jamming or hacking attempts. It could also protect trucks, ships and airplanes by ensuring they have reliable navigation.

On the home front, NAVSOP could lead to the equivalent of indoor GPS for firefighters trying to rescue people inside smoke-filled buildings or miners underground -- or even spelunkers who don't want to fall off the grid.

Risks of GPS Dependence                                                    

Overreliance on GPS signals is rampant in day-to -day life from data networks, financial systems, health networks, rail, road, aviation and marine transport, to shipping and agriculture. And military platforms commonly use GPS to find their position, navigate and execute missions.

With different systems sharing GPS dependency, a loss of signal could cause the simultaneous failure of many things people rely on daily.

Last year, the European Commission estimated that six to seven percent of its countries' GDP, representing a whopping $1 trillion, is already dependent on satellite radio navigation in Europe alone.

BAE and Lockheed aren’t the only ones working on a better more robust system. Other countries are developing their own systems, including the Russian GLONASS, Galileo for the European Union set to be completed in 2020 and COMPASS in China.

China began launching satellites last year, with its ultimate goal global navigation via 35 satellites by 2020.

Perhaps a better solution is already here on the ground?

Ballet dancer turned defense specialist Allison Barrie has traveled around the world covering the military, terrorism, weapons advancements and life on the front line. You can reach her at wargames@foxnews.com or follow her on Twitter @Allison_Barrie.