Tracking You Via TV Signals

By Roland Piquepaille

If you're inside a building, a GPS receiver cannot find you. But a $40 radio chip from Rosum Corporation will do it, with the help of TV signals. This start-up says that TV signals are 10,000 times stronger than GPS signals according to this article from Mercury News. Right now, these chips are at the prototype stage, but navigation products able to track an individual within a city should be available next year. And Rosum even thinks to integrate these radio chips in future cell phones. Meanwhile, the military envision to use the technology as a full GPS backup system or to track soldiers in dangerous environments. Obviously, privacy advocates warn that the technology could be used to locate and track people without their consent. Considering that one of Rosum's investors is In-Q-Tel, the investment arm of the CIA, we should look at this technology with caution. Read more...

Please read the full article for a complete background. Below are only short excerpts about the technology itself.

James Spilker, one of the original architects of the GPS satellite and founder of Stanford Telecommunications, launched Rosum in 2000 with Stanford University engineering Professor Matthew Rabinowtiz. They realized a synchronization feature in digital and analog television signals could be used for other purposes than to lock the vertical hold for older TVs.
The engineers created a radio receiver chip that could zero in on the TV signal and get the synchronization information. Using precision timing, they figure out how far a TV signal travels before it is picked up by a device equipped with Rosum chips. Next, they compare the measurements against other data that they collect with their own listening stations and then finally calculate the device's position. The Rosum engineers call this process "multilateration," which is akin to navigational triangulation.
To set up this system, customers have to put Rosum's radio chips and the modules that house them into their equipment. These modules, about as big as a matchbook, cost about $40 to make, but could become cheaper and smaller over time with high-volume production. One of the main computational tasks of these devices do is to filter out the wrong signals, such as ghost images that have been reflected off of an object.

Below is a diagram showing the Rosum TV-GPS system components (Credit: Rosum Corporation on this page) about their technology.

The Rosum TV-GPS system components
The Rosum RTMM is a chipset which can be integrated into the user device to be located or tracked. The RTMM contains a TV tuner module, a digital signal processing module, and other supporting glue logic and memory.

And according to these examples, the technology really works.

Rosum's vice president of engineering, Greg Flammel, says tests of the technology show it can track someone in the basement floor of the San Francisco Public Library. It also found a person in the heart of San Francisco's financial district.

So a question remains. If the technology works so well, can it be used by anyone to look after any other person?

Kurt Opsahl, staff attorney at the Electronic Frontier Foundation in San Francisco, said Rosum apparently will operate a location server that will be able to record the movement history of any device being tracked. If the Rosum technology eventually is built into cell phones or other popular gadgets, the government could subpoena Rosum's customers to track anyone's movements.
"This is another step toward a surveillance society," said Opsahl. "They could get your traffic patterns. This is fairly sensitive information."

Right now, if you want to spy on a specific person without his approval, you need to obtain a court order. So we might be safe from this intrusion for a while...

Sources: Dean Takahashi, Mercury News, May 9, 2005; and various websites

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