A method of calibrating output of an absolute atmospheric pressure sensor of an electronic device, comprising: Determining, at a processor of the electronic device, that a location of the electronic device is at a known absolute altitude and outdoors; Receiving, at the processor, a measured pressure from the absolute atmospheric pressure sensor; Calculating, at the processor, a difference between the measured pressure and a reference pressure, the reference pressure determined by adjusting a mean sea level pressure based on the known absolute altitude relative to mean sea level at the location of the electronic device; storing the difference, in a memory of the electronic device; and applying the difference to the output of the absolute atmospheric pressure sensor; wherein determination that the electronic device is at the known absolute altitude and outdoors occurs without user input, wherein the known absolute altitude is ground level and characterized in that determining that the location of the electronic device is at ground level and outdoors comprises: receiving, at the processor of the electronic device, motion sensor data of the electronic device; and receiving, at a GNSS sub-system of the electronic device in communication with the processor, GNSS signals, determining that for at least a threshold period of time the motion sensor data is indicative of a selected type of motion and the GNSS signals have a Signal-to-Noise ratio above a threshold. Determining, at a processor of the electronic device, that a location of the electronic device is at a known absolute altitude and outdoors; Receiving, at the processor, a measured pressure from the absolute atmospheric pressure sensor; Calculating, at the processor, a difference between the measured pressure and a reference pressure, the reference pressure determined by adjusting a mean sea level pressure based on the known absolute altitude relative to mean sea level at the location of the electronic device; storing the difference, in a memory of the electronic device; and applying the difference to the output of the absolute atmospheric pressure sensor; wherein determination that the electronic device is at the known absolute altitude and outdoors occurs without user input, wherein the known absolute altitude is ground level and characterized in that determining that the location of the electronic device is at ground level and outdoors comprises: receiving, at the processor of the electronic device, motion sensor data of the electronic device; and receiving, at a GNSS sub-system of the electronic device in communication with the processor, GNSS signals, determining that for at least a threshold period of time the motion sensor data is indicative of a selected type of motion and the GNSS signals have a Signal-to-Noise ratio above a threshold. receiving, at the processor of the electronic device, motion sensor data of the electronic device; and receiving, at a GNSS sub-system of the electronic device in communication with the processor, GNSS signals, determining that for at least a threshold period of time the motion sensor data is indicative of a selected type of motion and the GNSS signals have a Signal-to-Noise ratio above a threshold.