Location device a thing of wizardry

Mapping: AT&T scientists, using ultrasound techonology like bats use sonar, have a system to track people - look out, Harry Potter.

March 05, 2001|By Anne Eisenberg | Anne Eisenberg,NEW YORK TIMES NEWS SERVICE

Harry Potter, the star of the children's book series, has a Marauder's Map, with tiny moving symbols that show the location of everyone in his school. It is very handy when he is out late at night solving mysteries and wants to avoid bumping into enemies.

Now scientists have devised a real map that has a lot in common with Harry's magic one. Visitors can see it at the AT&T Laboratories in Cambridge, England, perhaps not far from Harry's home.

In a three-story, 10,000-square-foot space, AT&T staff members have developed a constantly updated map that can track people with ultrasound signals as they move through the building. It pinpoints their locations within inches, as long as they are wearing a small transmitter.

This ultrasound technology has a highly practical purpose: to track people moving through a hospital, factory or other building without encumbering them with computer gear. Since the system knows where the person is at all times, any nearby computer can be instructed to display the person's familiar desktop or data. It would be as if the desktop were following the person from machine to machine throughout the building.

The tagging of machines and people, and the coordination of these tags through a computer network, is one form of what is known as ubiquitous, or pervasive, computing. In such a world of networked buildings, communications and computer power would be constantly at hand as people moved around.

A doctor in a hospital, for example, would be able to call up important records quickly at a patient's bedside by using the nearest remote display.

For such technology to work, though, the system must be aware of exactly where the people are. It needs to know when someone walks over to a computer, telephone or microphone, not just when the person enters a room.

The ID Pete Steggles - one of the designers of the system - speaks of is the linchpin of the location system. It is a small device about 2 1/2 inches long that includes an ultrasound transmitter and a two-way radio.

The transmitters also are placed outside or on top of objects, like desktop computers, telephones and cameras, throughout the building. The rest of the system is embedded in the building, mainly in the form of ultrasound receivers tucked in every four feet or so above the tiles of the suspended ceiling. These receivers detect the pulses emitted to locate people and equipment.

A detector mounted on the far side of the room registers an ultrasound pulse later than a detector just above an object. "Using this differential timing information," Andy Hopper said, "it's possible to calculate the position of objects to about a cubic inch." Hopper is the managing director of the laboratory and an engineering professor at the University of Cambridge.

Hopper said the system - called Active Bat - uses the same principle as real bats, which send out high-frequency chirps, then navigate based on the location information they get from the reflected sound waves. With the AT&T system, the devices that are carried around (called bats by the researchers) emit the ultrasound chirps, and a high-speed network analyzes the signals it receives.

A central controller keeps its electronic eye out for any device that it knows is moving around the building. The new ultrasound system that makes this possible is related to AT&T Laboratories' experiences with an earlier infrared system called Active Badge.

AT&T is not yet making the ultrasound technology commercially available, although Steggles said many people have asked for it. "That's a few years away, once we've reduced the cost a bit by tinkering with it," he said.

Steven Feiner, a wearable-computers expert who is a computer science professor at Columbia University, agrees that the technology is likely to see wide use. But before that happens, Feiner said, "we'll have to deal with privacy - and it's going to be a very serious issue."

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