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Barometric altimeters on drones: how altitude is measured

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A barometric altimeter estimates altitude from air pressure, which falls as height increases. It is small, cheap and works without any outside signal, so nearly every flight controller carries one. Its readings are smooth over time but sensitive to weather and airflow, which is why it is almost always fused with other sensors.

How a barometer measures altitude

Air pressure decreases with height in a predictable way. A barometric sensor measures the local static pressure, and the flight controller converts that pressure into altitude using a standard atmosphere model.

For most drone flights what matters is altitude relative to the take-off point, so the controller records the pressure at take-off and measures changes from there.

Sources of error

A barometer measures pressure, not height, so anything that changes pressure without changing height shows up as altitude error:

  • Weather: atmospheric pressure changes over hours as weather systems move, causing slow drift.
  • Temperature: the sensor and the air around it change with temperature, which affects readings.
  • Propeller wash and airflow: air moving past the sensor at speed lowers or raises the measured pressure.
  • Ground effect: close to the ground, propeller downwash changes local pressure during take-off and landing.

Reducing the errors

Good placement and fusion make a large difference. Many builds shield the sensor with a small piece of open-cell foam to damp airflow and light. In software, the flight controller fuses barometric altitude with the accelerometer, which responds quickly but drifts, and, where fitted, with a rangefinder close to the ground or GNSS altitude when available.

Sensor fusion and the Kalman filter in drone navigation →

Role in GPS-denied navigation

When GNSS is unavailable, the barometer is one of the few sensors that directly bounds vertical error. Inertial navigation on its own drifts quickly in the vertical axis; a barometer keeps that drift in check. It also supplies the aircraft's own altitude for methods such as terrain-referenced navigation.

GPS-denied navigation: methods compared →

Frequently asked questions

Over short periods a barometer gives smooth relative altitude, but its absolute accuracy drifts with weather and temperature. That is why flight controllers fuse it with the accelerometer and, when available, a rangefinder or GNSS.

Common causes are airflow from the propellers reaching the barometer, temperature changes in the sensor, and slow changes in atmospheric pressure. Shielding the sensor with foam and tuning the altitude fusion usually help.

Yes. A barometer measures air pressure on board and needs no outside signal, which makes it an important sensor for navigation when GNSS is unavailable.