Pressure sensor correction
Calibration
Use a known elevation and a trustworthy independent QNH/barometer reference to correct the phone's pressure sensor.
What you need
You need two independent pieces of reference information:
- the elevation of the place where the phone is sitting; and
- a current, reliable local sea-level pressure / QNH / barometer reading.
The reference pressure should come from a nearby trusted weather or aviation source, not from Marine Barometer itself.
Finding elevation
Useful sources include:
- NRCan Toporama for Canada;
- Free Map Tools Elevation Finder for a quick worldwide lookup;
- topographic-map.com.
How calibration evolves
A single good reference point can correct the local offset. Marine Barometer retains calibration observations over time. When enough useful pressure span has accumulated, the calibration can also estimate a small sensor slope error while guarding against implausible changes and outliers.
The observations are the durable calibration evidence; derived correction values can be rebuilt from that history when the calibration algorithm changes.
Practical advice
Use stable conditions and good reference information. Small differences can come from the reference station's distance and elevation, weather gradients, temperature effects and timing. Calibration improves the phone sensor; it does not turn the phone into a laboratory transfer standard.