Welcome to the indoor positioning system (IPS)

Scientific American has an interesting post on how the global positioning system (GPS) has its limits in that roofs, walls and floors shield satellite signals and keep them from locating GPS receivers indoors. So - enter the indoor positioning system (IPS):

a budding technology that IPS manufacturers envision as one day tracking the movement of firefighters battling blazes inside burning buildings, patients in hospitals and even retail merchandise swiped from store shelves. Although this has sparked invasion-of-privacy fears in some, the technology itself is designed to deliver useful locator services that pick up where GPS leaves off.

Why can IPS go where GPS cannot? GPS technology relies on signals from multiple satellites and employs a triangulation process to determine physical locations with an accuracy of about 33 feet (10 meters); the most common forms of IPS, both in use and under development, employ radio, ultrasound or infrared signals to home in on enclosed locations.

Read in full - 'A Positioning System That Goes Where GPS Can't'