"We have laws covering privacy of medical and financial data, for example. We don't have laws that directly deal with location, because those technologies haven't been around long enough."
In fact, once people in the U.S. leave their homes, they have essentially no legal expectation of privacy, Gelman says.
"When you walk around in public, you are exposing yourself to view," she said. "Once you are exposed, you do not have the right to limit that exposure, which makes it hard to argue that you have a privacy interest in it."
The Walt Disney Company recently introduced Disney Mobile, a line of cell phones equipped with GPS technology that offers a host of family-friendly tools. The The Family Locator feature, for example, allows parents to track their kids in real time and display their locations on maps on the phones' screens.
Similar services on the market can even "geo-fence" children—the child's phone is tracked using GPS and can send an alert to Mom or Dad when it goes beyond predefined boundaries.
Also, current digital mapping technologies—such as the popular services Google Maps and Microsoft Live Local—already provide high-resolution overhead maps assembled from satellite images.
(Explore MapMachine: street, satellite, and theme maps online from National Geographic.)
As technology advances, these applications could expand to include more and better data in real time.
"The geospatial web is two or three things that are coming together," said Mike Liebhold, a senior researcher with the nonprofit Institute for the Future in Palo Alto, California.
"The first thing is the digital maps that have been around for a while. Now those maps will be combined with animations, photos, and [people's and businesses'] locations—latitudes and longitudes—attached to them."
(Related news: "Web Maps Offer Info, Aid to Katrina Victims" [September 12, 2005].)
But, the EPIC's Rotenberg says, it's not time yet to sound the alarm bells on improved digital maps or other such services.
"Even though it is an extraordinary technology that makes so much available, I don't think satellite imagery has yet reached the point where we're confronting the kinds of privacy issues that would give most people concern," Rotenberg said.
"You can't, for instance, [identify] a nude sunbather on a beach in France," he said.
Most satellite images, such as those displayed in digital mapping applications, are composites assembled over time and are not displayed in real time on the Internet, Rotenberg says.
In July a Google image of your neighborhood, for example, might show snow on the ground. That's because the satellite photos used in Google Maps are often taken months before they appear online.
Anonymity Is Key
But the geospatial web covers more than just satellite-based maps.
Some location-based services that are growing in popularity allow subscribers to tap into the wireless signals blanketing most urban areas and use them as a sort of homing beacon.
The Loki service, offered by Boston, Massachusetts-based firm Skyhook Wireless, allows users to triangulate their exact location using wireless signals picked up by their laptops, similar to the way GPS devices use signals from overhead satellites.
Loki users can get local weather reports; find nearby restaurants, movie theaters, or shops; and even share their locations with family and friends.
(Related news: "Mobile Games Superimpose Virtual Fun on the Real World" [October 16, 2006].)
Skyhook chief executive Ted Morgan says user privacy was one of the top considerations in developing the service.
"Most of these services and applications are being rolled out with privacy in mind, because you won't get a lot of usage if people are spooked or concerned that it could be used against them," he said.
Morgan also says that the company does not collect user information and that subscribing to Loki is a completely anonymous process—an aspect the firm added to their service after a review by privacy experts.
Allowing users to remain anonymous is key to protecting user privacy in a system like Loki, Liebhold, of the Institute for the Future, says.
"Any time you have to identify yourself to a network and say, Here I am, tell me about this place, there's the potential for privacy abuse," Liebhold said.
Without anonymity, he says, unwanted advertisers or other hackers could tap into users' personal information.
"Whether that data would be available to [other] people is not clear. It's a very murky area," he says.
Location-based techniques can also benefit companies interested in tracking assets such as fleet vehicles, but this introduces questions regarding a worker's right to privacy on the job.
"Certainly employers have an interest in knowing where people are and what they're doing, and in managing the company assets," EPIC's Rotenberg said.
"But these techniques can be very intrusive. To always know where someone is, is more information than most employers are entitled to," he said.
Such a scenario is another place where the law needs to catch up, he says.
While employee privacy codes have been established in Europe and elsewhere, those kinds of protections have not been set up in the United States.
"The big question in this area is, As technology advances, does privacy diminish?" Rotenberg said.
Not necessarily, he says, as long as users are able to control who can access their personal information.
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