The barometric altitude measurement using modern electronic sensors has significant error due to atmospheric pressure variations with respective to weather and time. Based on the altimeter setting concept, the barometric altimeter should be corrected according to hourly QNH data to maintain accuracy. This paper presents an airborne altitude measurement technology using barometric measurement and real time calibration through GPRS uplink. The proposed method is practical in correcting the time variant error of the electronic barometric altimeter automatically. After these corrections, the static and dynamic accuracy of the electronic barometric altimeter can be much improved into less than 2% errors in real time. The proposed system is suitable for ultra light aircrafts (ULA) or unmanned aerial vehicles (UAV).