Can you be found anywhere, anytime?
Most of us know where we are on planet Earth - or close enough to make do. But sometimes we travel on business or for pleasure and suddenly wonder: Where am I? Or maybe we might want to know the location of a spouse, teenager, or pet.
More and more, GPS - the global positioning system - is coming to the rescue. But the satellite-based system has one big drawback: Its signals can't reach inside buildings or down into the skyscraper-lined streets of major cities, where millions of people live or work.
The result? One of the era's breakthrough technologies - tracking the location of everything from packages to cellphone users in distress - remains impractical to much of the population. Now that appears likely to change.
Racing to fill in the gaps where GPS can't reach, companies are experimenting with various wireless technologies. Solutions can't come too soon. The federal government has charged mobile-phone companies, even the ones that are Internet-based, to make their phones capable of being located when a user dials 911 for help.
But such tracking technology also raises privacy concerns, which are likely to heighten as the technology spreads. Some groups already worry about who will know where you are - and what they might do with the information.
One obvious solution to the gapsin GPS is an alternate, urban-friendly technology.
Among those bidding to provide that answer is Rosum Corp. in Redwood City, Calif. The five-year-old start-up has a simple plan: In urban areas, many commercial TV signals blanket the airwaves. The transmitting locations are known. Just plot the time it takes for several of the signals to reach you, and you can determine your location.
TV signals are already designed for indoor reception. "We're taking advantage of that," says Jon Metzler, director of business development for Rosum.
The quality of the signal doesn't have to be good enough to produce a TV picture, just strong enough to reveal where it's coming from, he says.
With about 1,300television towers in the United States and nearly 1,900 over-the-airwaves TV stations, most of urban and suburban America is covered with TV signals. Where Rosum is weakest, in rural areas with open skies, happens to be where GPS works best.
Rosum officials hope to have their product commercially available soon. Among its backers is In-Q-Tel, the venture capital arm of the Central Intelligence Agency. "We're obviously very happy with their interest," Mr. Metzler says.
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