In various embodiments, crowd sourcing techniques are provided to determine beacon altitudes that may then be used in 3D positioning of UE. Some techniques may crowd source beacon altitudes based on global navigation satellite system (GNSS) position fixes obtained by UE. Other techniques may crowd source beacon altitudes based on uncalibrated pressure measurements obtained by UE. Still other techniques may combine beacon altitude crowd-sourcing and pressure sensor calibration on UE. Such techniques may make inferences based on line of sight (LOS) between UE and beacons, determined using signal strength, connection status, and/or timing measurement. The techniques may be implemented separately, or as part of a combined system that determines beacon altitudes in diverse manners. Once beacon altitudes are known, that may be used to determine 3D positions of the UE (e.g., by trilateration, multilateration or other positioning techniques).