Vertical errors of GPS (Global Positioning System) may grow more than 20 meters in urban area due to navigation satellite visibility. In this paper, we propose a novel method to integrate a low-cost barometric altimeter and a GPS receiver to reduce GPS vertical errors. Barometric pressure measured by a barometric altimeter is largely affected by weather conditions. Measured barometric pressure is changed continuously even when the corresponding true height is constant. For the reason, the barometric altitude assuming a standard atmosphere bears large height errors. To reduce the barometric altitude error, the proposed method in this paper utilizes the real time sea-level pressure and temperature data provided by the meteorological agency. In addition, the difference between the geoidal height and ellipsoidal height is considered. A simple Kalman filter algorithm is formulated to integrate the barometric altitude and the GPS height.

Keywords: GPS, barometric altimeter, Kalman filter