Barometric and GPS altitude sensor fusion

The altitude of a moving vehicle as reported by GPS suffers from intermittent errors caused by temporary obstruction of the satellites by buildings, mountains, etc. Additionally, it is affected by systematic errors caused by multipath effects, ionospheric and tropospheric effects, and other hardware design limitations and natural factors. Atmospheric pressure, measured by a portable barometric sensor, could also be used to determine altitude, is not susceptible to problems caused by obstruction of satellites, and can provide reliable measurements outdoors even in urban and mountainous regions. In this paper, we propose an algorithm which improves accuracy and provides tighter confidence bounds of altitude measurements from a mobile phone (or any device equipped with GPS and barometric sensors) by means of sensor fusion techniques without the need for calibration. Our experiments have shown that the proposed algorithm provides more accurate measurements with tighter confidence bounds compared to using either of the two sensors, barometric or GPS, alone.