Barometric and GNSS altimeters: why measure altitude and pressure during sampling and testing?

Essential in the field as well as in the lab, the altimeter records the altitude and atmospheric pressure associated with your samples. This metadata enhances traceability, enables physicochemical corrections (e.g., O? saturation, boiling point), and contextualises time-series data. Depending on your needs, choose a barometric model (pressure measurement converted to altitude), GNSS (multi-constellation GPS) or a hybrid with sensor fusion. Portable versions often include data logging, Bluetooth/USB interfaces, IP65/IP67 housings and extended battery life for long field campaigns.

What different types of altimeters are there, and how do they work?

• Barometric altimeters. A MEMS sensor or an aneroid capsule measures the pressure (hPa) and then applies the barometric formula to compute altitude. Pros: excellent responsiveness, very good relative resolution (down to a few tens of cm), low power consumption. Limits: pressure varies with the weather; a calibration (known elevation or QNH) and temperature compensation are recommended for absolute accuracy.

• GNSS altimeters (GPS/Galileo/GLONASS/BeiDou). Height is determined by satellite positioning. Pros: absolute altitude without depending on weather pressure; no barometric drift. Limits: typical vertical accuracy of 3 to 10 m (better with multi-frequency/SBAS/RTK), sensitivity in dense urban areas, forests or indoors.

• Laser / ultrasonic altimeters. Measure the ground distance (radar/laser/US) for the relative altitude of platforms (e.g. drones). Pros: decimetre- to centimetre-level precision at short range. Limits: limited range, need for a line of sight.

• Hybrid systems and data loggers. Many instruments combine baro + GNSS and add logging (adjustable interval), time-stamping GPS, Bluetooth to a mobile app, altitude profiles, alarms and CSV exports. IP65/IP67 enclosures, extended operating temperatures and sunlight-readable displays make field campaigns easier.

Selection criteria: absolute vs relative accuracy, stability and response time, logging options, battery life (Li-ion battery/cells), ruggedness (drops, IP), connectivity, weight/size, and traceable calibration services.

Type	Principle	Applications
Barometric	Pressure ? altitude	Relative precision, altitude profiles, long battery life
GNSS	Multi-GNSS satellites	Absolute altitude, sample georeferencing
Laser/US	Ground distance	Drones, proximity measurements, approach safety

In which fields is an altimeter used?

• Life sciences and ecology: contextualising a sample (fauna, flora, water) with altitude informs interpretation (species distribution, thermal gradients, dissolved O?).
• Environment and water: linking pressure/altitude to physico-chemical measurements (pH, conductivity, DO) to apply corrections and compare sites.
• Agri-food and viticulture: map microclimates and terroirs, monitor sloping plots, document crop-management workflows.
• Industry, chemicals, cosmetics, pharmaceuticals: georeference audits and quality sampling, drone site inspections (safe relative altitude), logistics at elevation.
• Research & teaching: altimetric profiles for practicals/fieldwork, validation of local atmospheric models.

The different types of altimeters available

Altimeter

Frequently asked questions about altimeters

What accuracy can you expect from a barometric altimeter?
In relative terms, resolution can be sub-metre. Absolute accuracy depends on the pressure setting (QNH) and on weather conditions.

GNSS or barometric: which should you choose?
For absolute altitude, GNSS is appropriate. For fine profiling and responsiveness, the baro sensor is ideal. Hybrid systems combine the benefits.

How often should it be calibrated?
Check on every outing against a known point (benchmark/map height) and schedule an annual, traceable calibration in line with your quality requirements.

How can you improve barometric accuracy?
Enter the local QNH, enable temperature compensation, and avoid abrupt changes (openings/wind) during measurement.

Does a GNSS altimeter work in dense forest?
Vertical accuracy can degrade. Favour multi-GNSS, a quality antenna and, if possible, a fused solution with a baro sensor.

Can you record and export the data?
Yes, data-logger models store time-stamped points and export as CSV via USB or Bluetooth to software or a mobile app.

Which IP ratings should you aim for in the field?
IP65 protects against water jets; IP67 tolerates brief immersion. Choose according to rain, dust and frequency of use.