Using barometers to determine the height for indoor positioning

Abstract

It is well known that atmospheric pressure decreases when altitude increases. Models have been created to relate altitude or height to pressure. A barometer can measure the air pressure and then the altitude can be calculated. Before the era of GNSS, barometers were widely used to determine heights outdoors. The invention of GNSS was a revolution in positioning and navigation. However, it does not work in an indoor environment. Alternative technologies have been developed such as Wi-Fi fingerprinting mainly for 2D positioning and navigation. In some of the applications, 3D or 2.5D (the level of the building) is required. Using barometers is a possible solution and some new mobile phones have a built in pressure sensor. But there are many issues that should be considered. Is height determined from barometric pressure accurate enough? Is there a latency problem? Does the air conditioning in an almost sealed building significantly affect height readings? This paper discusses the necessary considerations to use barometers for indoor applications based on experiments. Possible solutions are suggested.