ATLANTA (AP) -- Satellite-based navigation gadgets can guide motorists from high above, saving bumbling drivers countless hours and extra trips to the gas station. But directing people on a much smaller scale - such as inside an office - is a much greater challenge.

Locator equipment based on Global Positioning System satellites is accurate to about 10 feet - fine for drivers searching for the next right turn but not for pedestrians seeking a front door. And the range of GPS is limited indoors, and it can't on its own differentiate between a path and a wall.

Georgia Institute of Technology researchers are trying to pick up where GPS leaves off. Its System for Wearable Audio Navigation, or SWAN, consists of a wearable computer connected to a headband packed with sensors that help sight-impaired users know where they are and how to get where they're going.

Besides a pendant-sized wireless GPS tracker, there are light sensors and thermometers that help distinguish between indoors and outdoors. Cameras gauge how far away objects and obstacles are. A compass establishes direction. And an inertia detector tracks the roll, pitch and yaw of the user's head.

All the data are crunched by a computer in a backpack, which relays high-pitch sonar-like signals that direct users to their destinations. It also works with a database of maps and floor plans to help pinpoint each sidewalk, door, hall and stairwell...