Tracking people: TV signals go where GPS can't
By Dean Takahashi
Mercury News
Even if you're lost, Rosum will find you. That's the promise of the Redwood City start-up that has figured out how to use television signals to track your whereabouts.
Rosum's technology complements the satellite-based global positioning system. The decades-old GPS, originally built for military purposes, can get a fix on gadgets equipped with GPS receivers -- as long as you're out in the open. But GPS doesn't work well in skyscraper-filled urban canyons and it doesn't work at all inside buildings.
But TV signals penetrate through buildings, and Rosum uses them to track people where GPS can't. The first device using Rosum's technology is in the prototype stage. Navigation products using it will make their debut next year, according to Rosum Chief Executive Skip Speaks.
``There are immense black holes in the GPS system, and we can fill the gap,'' says John Metzler, Rosum's director of business development.
Rosum, which counts among its investors In-Q-Tel, the investment arm of the Central Intelligence Agency, promises a vast improvement in location-tracking services and gadgets. That could help everyone from the military to dispatchers tracking delivery trucks. It could even be used to track parolees like Martha Stewart when they go indoors, or locate someone making a 911 emergency call on an Internet phone.
``If you are tracking a van going up the 101, it goes dark in the financial district,'' says Metzler. ``With us, you can have the security of knowing where the van is, and if the driver has stopped to get doughnuts.''
Adds Speaks, the former head of Kyocera's wireless phone business, ``Ultimately, we'd like to drive the technology into every cell phone.''
But privacy advocates raise a red flag about how Rosum's technology could be used to locate and track people without their consent.
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.''
Speaks says it will be up to Rosum's customers to decide how to implement the technology and balance privacy concerns. He says anyone tracking a specific person without that individual's approval must obtain a court order.
``We will give up some of our privacy for enhanced security,'' he says.
He notes, for instance, that a Rosum network could be set up to monitor the locations of soldiers, police or firefighters as they go into dangerous buildings. If they need to be rescued, it would be easier to locate them with the Rosum technology.
Commercial use of GPS satellites began in 1991 but James Spilker, one of the original architects of the GPS satellite, knew its weakness well.
Spilker, the 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.
``That's the part that took a lot of Stanford Ph.D.s,'' Speaks says.
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.
Flammel says TV signals are 10,000 times stronger than GPS signals. That means tracking through TV signals is much easier and quicker than via satellite.
Mark research firm Frost & Sullivan estimates the market for GPS equipment -- now at $445 million -- will double in the next six years.
There also are strategic uses for Rosum's technology. President Bush signed a directive in December requiring the government to find an alternative to GPS in case the system is compromised. Speaks says Rosum's positioning technology could serve as the GPS backup system.
Among the investors in Rosum, which has raised $16 million, is In-Q-Tel, Charles River Ventures, Allegis Capital, Motorola Ventures, Steamboat Ventures and KTB Ventures. Rosum says it has won nine patents and has applied for dozens more.
Rosum, which has only 27 employees, has a partnership with Sunnyvale-based Trimble Navigation to make a fleet-tracking device that would use both GPS and the Rosum TV-tracking system. Trimble expects to launch that product next year.
``The tests we've done show it works even in the basements of big buildings,'' said Dennis Workman, a vice president of component technologies at Trimble.
Rosum is best used with a GPS system, mainly because TV signals don't reach into places such as the Nevada desert or the middle of the ocean. The technology also isn't useful for tracking someone vertically. So it can locate a person in an office tower but can't determine what floor they're on unless the building is ringed with a set of Rosum antennas.
``We aren't going for the commodity markets at first,'' says Speaks. ``But you have to ask, what things do you really want to locate? What is it worth to have a 911 call that you can track regardless of what kind of phone initiates it?''
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