Piezoelectric barometer could provide indoor elevation data on your phone

Ars Technica : Smartphones use GPS and Wi-Fi signals to provide geographic location data. However, they don’t tend to work inside large buildings, where GPS signals are often blocked, and Wi-Fi access points can shift. To help track a smartphone user in a multistory building, a team of researchers in Japan has now developed a miniaturized barometer. They placed a tiny piezoelectric cantilever over the opening of a similarly tiny chamber. The cantilever bends in response to pressure differences between the chamber and the outside air. Because the cantilever is made of a piezoelectric material, the bend creates a measurable change in its electrical resistance. The change in resistance can be calibrated to serve as a measure of the air pressure change. And the device is sensitive enough to distinguish changes in pressure due to elevation differences between just two floors. Because the barometer uses relative changes in pressure, it won’t be affected by weather. Nevertheless, errors can accumulate over time.