By Humphrey Hawksley
BBC News, Washington
The US and UK governments are developing increasingly sophisticated gadgets to keep individuals under their surveillance. When it comes to technology, the US is determined to stay ahead of the game.
Humphrey Hawksley's data is captured by a camera in one second
"Five nine, five ten," said the research student, pushing down a laptop button to seal the measurement. "That's your height."
"Spot on," I said.
"OK, we're freezing you now," interjected another student, studying his computer screen. "So we have height and tracking and your gait DNA".
"Gait DNA?" I interrupted, raising my head, so inadvertently my full face was caught on a video camera.
"Have we got that?" asked their teacher Professor Rama Chellappa. "We rely on just 30 frames - about one second - to get a picture we can work with," he explained.
I was at the University of Maryland just outside Washington DC, where Professor Chellappa and his team are inventing the next generation of citizen surveillance.
They had pushed back furniture in the conference room for me to walk back and forth and set up cameras to feed my individual data back to their laptops.
Gait DNA, for example, is creating an individual code for the way I walk. Their goal is to invent a system whereby a facial image can be matched to your gait, your height, your weight and other elements, so a computer will be able to identify instantly who you are.
"As you walk through a crowd, we'll be able to track you," said Professor Challappa. "These are all things that don't need the cooperation of the individual."
How you walk could be used to identify you in a crowd
Since 9/11, some of the best scientific minds in the defence industry have switched their concentration from tracking nuclear missiles to tracking individuals such as suicide bombers.
My next stop was a Pentagon agency whose headquarters is a drab suburban building in Virginia. The Defence Advanced Research Projects Agency (Darpa) had one specific mission - to ensure that when it comes to technology America is always ahead of the game.
Its track record is impressive. Back in the 70s, while we were working with typewriters and carbon paper, Darpa was developing the internet. In the 90s, while we pored over maps, Darpa invented satellite navigation that many of us now have in our cars.
"We ask the top people what keeps them awake at night," said its enthusiastic and forthright director Dr Tony Tether, "what problems they see long after they have left their posts."
"And what are they?" I asked.
He paused, hand on chin. "I'd prefer not to say. It's classified."
"All right then, can you say what you're actually working on now."
"Oh, language," he answered enthusiastically, clasping his fingers together. "Unless we're going to train every American citizen and soldier in 16 different languages we have to develop a technology that allows them to understand - whatever country they are in - what's going on around them.
"I hope in the future we'll be able to have conversations, if say you're speaking in French and I'm speaking in English, and it will be natural."
"And the computer will do the translation?"
"Yep. All by computer," he said.
"And this idea about a total surveillance society," I asked. "Is that science fiction?"
"No, that's not science fiction. We're developing an unmanned airplane - a UAV - which may be able to stay up five years with cameras on it, constantly being cued to look here and there. This is done today to a limited amount in Baghdad. But it's the way to go."
In Britain we are monitored 24/7 by four million CCTV cameras
Interestingly, we, the public, don't seem to mind. Opinion polls, both in the US and Britain, say that about 75% of us want more, not less, surveillance. Some American cities like New York and Chicago are thinking of taking a lead from Britain where our movements are monitored round the clock by four million CCTV cameras.
So far there is no gadget that can actually see inside our houses, but even that's about to change.
Ian Kitajima flew to Washington from his laboratories in Hawaii to show me sense-through-the-wall technology.
"Each individual has a characteristic profile," explained Ian, holding a green rectangular box that looked like a TV remote control.
Using radio waves, you point it a wall and it tells you if anyone is on the other side. His company, Oceanit, is due to test it with the Hawaii National Guard in Iraq next year, and it turns out that the human body gives off such sensitive radio signals, that it can even pick up breathing and heart rates.
"First, you can tell whether someone is dead or alive on the battlefield," said Ian.
"But it will also show whether someone inside a house is looking to harm you, because if they are, their heart rate will be raised. And 10 years from now, the technology will be much smarter. We'll scan a person with one of these things and tell what they're actually thinking."
He glanced at me quizzically, noticing my apprehension.
"Yeah, I know," he said. "It sounds very Star Trekkish, but that's what's ahead."
From Our Own Correspondent was broadcast on Saturday, 15 September, 2007 at 1130 BST on BBC Radio 4. Please check the programme schedules for World Service transmission times.