The watch contains an internal altimeter and barometer. The watch collects elevation and pressure data continuously, even in low-power mode. The altimeter displays your approximate elevation based on pressure changes. The barometer displays environmental pressure data based on the fixed elevation where the altimeter was most recently calibrated (Altimeter and Barometer Settings). You can view the altimeter and barometer from the controls menu (Controls), glances list (Glances), or apps list (Apps).