Techniques of altitude determination by user equipment (UE) in a mobile communications network are discussed. A request for calibration data is transmitted to a node of the network. Barometric calibration data is received at the UE. A barometric pressure sensor in the UE measures a barometric pressure value based on the barometric calibration data. Measuring the barometric pressure value using the barometric pressure sensor in an embodiment comprises adjusting a measured barometric pressure value that is measured using the barometric pressure sensor. The barometric pressure value is transmitted to the node. The UE receives a second part of the barometric calibration data, and in dependence of the second part of the barometric calibration data and/or in dependence of the measured barometric pressure value, determines an altitude of the user equipment.