Criminal gangs have begun using GPS “jammers” imported from China to help them steal expensive cars and lorries carrying valuable loads – and there are fears that terrorists could use more powerful versions to disrupt air traffic, a conference in London will hear on Tuesday.

The “jammers” put out radio signals at the same frequency at the Global Positioning System (GPS) satellites, overwhelming the timing signal that in-car devices use to plot their position. That means a tracker device built into a lorry with a valuable load, or a car with an anti-theft GPS device which should report its position if stolen, cannot distinguish the correct GPS signal.

“It disappears from the radar,” said Professor David Last, of the University of Wales at Bangor, who has been a police expert witness in a number of cases over the past 18 months in which GPS jammers have been seized.

Satnav devices rely on being able to “see” at least four of the 30 satellites orbiting about 20,200km (12,550 miles) above the earth: by correlating the very precise timing and identification signals they transmit, a ground-based device can calculate its own location to within about 1 metre. However, the jamming devices do not have to put out a strong signal to disrupt GPS reception.

“The problem is that the signal from the satellites is extremely weak – it’s the equivalent of picking up the light output of a 25-watt bulb on the satellite,” said Bob Cockshott, another conference speaker who heads the location and timing program for the Technology Strategy Board, funded by the Department of Business, Innovation and Skills.

“That means you only need a jammer with an output of about 2 watts to swamp any signal from the GPS satellites over an area of a few metres.” Such a device would be billions of times more powerful than the GPS signal at ground level.

Article courtesy: Guardian Newspaper UK

When the road disappeared after a hairpin turn, I knew this was definitely not going according to plan.Then again, nothing about our evening ride back to San Francisco was turning out as expected, a source of no small irritation to my increasingly irritated wife.

Let me back up.

When it comes to finding my way, I’m no Daniel Boone, but I’m not a complete dork, either. Inside the family, there’s no small difference of opinion about that claim. For the sake of matrimonial harmony, I’ll leave it at that. (Though for the record: my wife’s navigational prowess will hardly ever be confused with that of either Lewis or Clark.) But let’s not quibble about the clear conclusion: Chez Cooper was a prime candidate for some off-the-shelf technology help.

On vacations, I’ve rented cars with built-in global positioning systems units on several occasions. No complaints with the experience. So over the holidays, I decided to surprise my better half with a Garmin GPS.

That’s when the fun really began.

Garmin sells a simple and reliable device. Unfortunately, it doesn’t relieve you of the responsibility for using your brain. A certain somebody (no names, here) had programmed the device to calculate the route based on the shortest route. As I was about to discover, the shortest route did not come close to approximating the shortest time.

The Sunday evening traffic on Interstate 80 was particularly heavy as it coincided with the end of the Christmas-New Year’s break. Many vacationers returning to San Francisco from Lake Tahoe added to the congestion as I pointed my car south upon leaving Folsom, a city about 120 miles away from San Francisco.

With everyone in the car dozing quietly, the Nuvi instructed me to exit the highway long before we were scheduled to reach the bridge entrance to the city. That seemed odd. Our plan was to first stop in Oakland to drop off a friend, who had spent the day with us.

“Hey, the Nuvi knows,” I said to myself. “And I’m not going to second guess my co-pilot.”

That opinion was not fully shared by the backseat drivers in the car, who, by this time, had stirred from their slumber. Why was I getting off at the wrong exit, they wanted to know. “Do you know where you’re going?”

It’s not the wrong exit, I said. “It’s a shortcut that the GPS calculated. Trust me.”

My curt response cost me dearly after the “shortcut” turned into a 10-mile-long stop-and-go parking lot. I can’t blame the Nuvi for that one. In time, the traffic let up and we were back on our way toward our destination. Before long, the sign for Oakland appeared up ahead.

But the Nuvi, still in shortcut mode, ignored the turnoff. Then so did I.

“What are you doing?” my wife asked in a tone usually reserved for those special occasions where yours truly screws up big time.

I rolled my eyes.

“Relax, the Nuvi knows what it’s doing. Let’s just follow the route. OK?”

Ever fantasize about having the ability to wind back the clock and retract some of the more egregiously dumb statements you’ve ever uttered? This was one of those times. A few minutes later the Nuvi had us rolling through pitch black country roads that rose and fell in rhythm with the undulating terrain of Northern California.

We had no idea where we had landed, other than that it was in the wrong place. Still, the Nuvi was confidently talking up a storm. Turn left here, turn right there–no crisis of confidence on the part of the GPS.

My wife, on the other hand, was having a royal fit. When the road narrowed to a single car’s width and we were forced to navigate a series of 90-degree turns above an escarpment, she dug her nails into my arm.

“The GPS is taking us in the opposite direction,” she said. “Can you understand that?”

I nodded. This time I kept my big mouth shut. The road–and I’m being charitable by describing it as such–meandered for miles with nary a sign of civilization. We did come across a couple of very surprised cows, who scattered without much persuasion.

The country road eventually hooked up with the Oakland hills and the rest of the journey proved uneventful, ignoring the inevitable lecture my wife delivered after we dropped off our friend at her house.

Article courtesy cnet news: http://news.cnet.com/8301-10787_3-10144883-60.html

‘He followed the system to the letter’ – prosecutor

‘I had no reason not to trust it’ – Jones