Primary instrument
Barometer
A sea-level-corrected pressure display intended to read like a familiar analog instrument.
Reading the dial
The phone sensor measures local station pressure. Marine Barometer corrects the calibrated sensor reading to sea-level pressure using the reference elevation. The result is the familiar barometer value used for weather comparison.
The pressure units can be switched between hPa and inHg.
Reference needle
The reference needle is a simple visual trend marker. Set it to the current pressure, then look again later. A live needle above the reference indicates a rise; below the reference indicates a fall. It does not affect the pressure calculation.
Pressure and movement
Atmospheric pressure and elevation both affect the sensor. Taking the phone up or down a hill can look like a rapid weather change if the app is logging. For a clean home pressure record, pause logging when you leave the reference elevation and resume it when you return.
Calibration
Calibration corrects the phone's pressure sensor against an independent pressure reference. Marine Barometer keeps calibration observations so the correction can be rebuilt when the calibration algorithm changes.