As part of our course, we designed and built custom drones for research purposes. The following section provides an overview of their potential applications, scientific value, and practical limitations in operation.

Volcanological research faces a basic observational dilemma: the most informative places—active vents, lava domes, fresh lava flows, and eruption plumes—are often too dangerous or inaccessible for scientists. Unoccupied aircraft systems (UAS), commonly called drones, occupy the scale between fixed ground stations, satellites, and crewed aircraft. They can be deployed quickly, fly repeated low-altitude trajectories, and carry cameras, spectrometers, gas sensors, meteorological probes, magnetometers, or sampling devices. Their principal scientific advantage is therefore not simply a reduction in cost. Drones can obtain spatially resolved in situ measurements while keeping personnel outside the most hazardous zone, and they can repeat the same survey often enough to reveal change.

Volcanic gases: composition, flux, and magma processes

Volcanic-gas measurements are among the most important drone applications. Carbon dioxide (CO₂), sulfur dioxide (SO₂), water vapour, hydrogen sulfide, and halogen species provide indirect information about magma storage, ascent, and degassing. In particular, temporal changes in ratios such as CO₂/SO₂ can reflect the depth and evolution of the degassing source, although no single gas ratio is a deterministic eruption predictor. Instrumented drones can cross a plume at several heights, record gas concentration together with position and wind, and thereby estimate both composition and emission flux. The first published UAV measurements of volcanic CO₂ flux were made at La Fossa crater on Vulcano, Italy. A helicopter UAV carried ultraviolet, infrared, and electrochemical instruments; combining the measured SO₂ flux with the CO₂/SO₂ ratio yielded an estimated CO₂ flux of 170 metric tons per day (McGonigle et al., 2008).

Later systems extended this concept from short multicopter flights to long-range and beyond-visual-line-of-sight missions. At Manam volcano in Papua New Guinea, aerial measurements were integrated with ground-based spectroscopy and satellite observations to determine multi-species gas fluxes at a strong but previously poorly characterised emitter. The campaign also enabled near-real-time plume chemistry and collection of samples for carbon-isotope analysis (Liu et al., 2020). Miniaturisation now permits useful SO₂ and CO₂ measurements with platforms weighing little more than one kilogram (Karbach et al., 2022). Drones can also carry bags or flasks rather than only electronic sensors. At Aso volcano, a sampler used an SO₂ threshold to trigger a pump inside the plume; radio telemetry then helped the operator position the aircraft in gas-rich regions and recover samples suitable for isotope analysis (Tsunogai et al., 2022).

Photogrammetry, thermal imaging, and eruption dynamics

A second major application is high-resolution mapping. Overlapping RGB photographs can be processed with Structure-from-Motion photogrammetry to create georeferenced orthomosaics, dense point clouds, and digital elevation models (DEMs). Repeated DEMs allow researchers to calculate lava-flow thickness and volume, dome extrusion rates, erosion, crater growth, fissure opening, or flank deformation. During the 2017 eruption of Mount Etna, two UAV surveys acquired almost 1,170 images over an active lava field. The resulting map supported civil protection work, while the DEM enabled an erupted-volume estimate of approximately 1.4 million cubic metres (De Beni et al., 2019). Such centimetre-scale products fill an important gap: satellite data cover large areas but often lack comparable detail, whereas terrestrial surveys may not have a safe line of sight.

Thermal cameras add information that visible imagery cannot provide. They can locate hot cracks, active fumaroles, lava channels, newly exposed dome material, and hydrothermally altered zones. At Merapi, drone photogrammetry and thermal observations identified a fractured, thermally active sector of the lava dome. Stability and flow modelling indicated that failure of this sector could generate a block-and-ash flow travelling several kilometres, demonstrating how drone data can feed directly into hazard scenarios (Darmawan et al., 2018). Video and topographic mapping can also address eruption physics. At the 2014–2015 Holuhraun eruption in Iceland, UAV-derived topography was combined with observations of lava fountains to relate changing vent activity to the morphology of growing spatter cones and to infer properties of the shallow feeder system (Witt et al., 2018).

Ash, aerosols, and geophysical surveys

Drones are increasingly used as mobile laboratories inside volcanic clouds. The AeroVolc system, deployed at Sakurajima and Etna, combined custom ash collectors, optical particle counters, and gas sensors. It recovered grain-size distributions and evidence of particle aggregation while measuring PM₁, PM_2.5, PM₁₀, SO₂, and CO₂ (Thivet et al., 2025). These observations improve models of plume dispersion and sedimentation and are relevant to aviation, air quality, and atmospheric chemistry. Other payloads extend drones beyond imaging and chemistry. Lightweight magnetometers can map contacts between volcanic units and detect anomalies associated with thermal or intrusive structures; repeated low-altitude surveys may reveal temporal change that is difficult to capture from the ground (Gailler et al., 2021). Drones can additionally deploy temporary sensors or retrieve ash and gas samples from locations that would otherwise require high-risk fieldwork.

Limitations and the role of drones in monitoring systems

Volcanic environments are unusually hostile to aircraft. Strong winds, plume turbulence, low air density at high elevation, corrosive gases, moisture, heat, and ash all reduce reliability. Ash is not merely an imaging nuisance: an sUAV at Stromboli suffered motor blockage after ash entered its rotating motors, causing an uncontrolled landing (Brosch, 2022). Battery endurance and payload remain tightly coupled, and long-range flights may require regulatory approval for operations beyond visual line of sight. Measurement quality also requires care. Rotor downwash can disturb particles and dilute local gas concentrations; low-cost sensors may respond slowly, drift, or show cross-sensitivities; wind fields within a plume are heterogeneous; and reliable photogrammetry requires accurate georeferencing and sufficient image overlap. Good deployments therefore use calibrated instruments, background measurements, synchronised meteorological data, explicit uncertainty estimates, conservative weather limits, and flight plans that treat loss of the aircraft as a credible event.

Drones consequently do not replace observatories, satellites, or ground instruments. Their value lies in connecting these systems: they provide the local detail missing from satellite products, the spatial context missing from fixed stations, and direct samples that remote sensing cannot supply. Used repeatedly and integrated with seismic, deformation, thermal, and satellite data, UAS can improve both process research and operational hazard assessment.

References

• Brosch, E. (2022). Volcanic ash and small uncrewed aerial vehicle (sUAV) interaction: In situ observations and laboratory experiments on aircraft failure. Frontiers in Earth Science, 10, 810962. https://doi.org/10.3389/feart.2022.810962
• Darmawan, H., Walter, T. R., Troll, V. R., & Budi-Santoso, A. (2018). Structural weakening of the Merapi dome identified by drone photogrammetry after the 2010 eruption. Natural Hazards and Earth System Sciences, 18, 3267–3281. https://doi.org/10.5194/nhess-18-3267-2018
• De Beni, E., Cantarero, M., & Messina, A. (2019). UAVs for volcano monitoring: A new approach applied on an active lava flow on Mt. Etna (Italy), during the 27 February–02 March 2017 eruption. Journal of Volcanology and Geothermal Research, 369, 250–262. https://doi.org/10.1016/j.jvolgeores.2018.12.001
• Gailler, L., Labazuy, P., Régis, E., Bontemps, M., Souriot, T., Bacques, G., & Carton, B. (2021). Validation of a new UAV magnetic prospecting tool for volcano monitoring and geohazard assessment. Remote Sensing, 13(5), 894. https://doi.org/10.3390/rs13050894
• Karbach, N., Bobrowski, N., & Hoffmann, T. (2022). Observing volcanoes with drones: Studies of volcanic plume chemistry with ultralight sensor systems. Scientific Reports, 12, 17890. https://doi.org/10.1038/s41598-022-21935-5
• Liu, E. J., Aiuppa, A., Alan, A., et al. (2020). Aerial strategies advance volcanic gas measurements at inaccessible, strongly degassing volcanoes. Science Advances, 6(44), eabb9103. https://doi.org/10.1126/sciadv.abb9103
• McGonigle, A. J. S., Aiuppa, A., Giudice, G., Tamburello, G., Hodson, A. J., & Gurrieri, S. (2008). Unmanned aerial vehicle measurements of volcanic carbon dioxide fluxes. Geophysical Research Letters, 35, L06303. https://doi.org/10.1029/2007GL032508
• Thivet, S., Bagheri, G., Kornatowski, P. M., et al. (2025). In situ volcanic ash sampling and aerosol–gas analysis based on UAS technologies (AeroVolc). Atmospheric Measurement Techniques, 18, 2803–2824. https://doi.org/10.5194/amt-18-2803-2025
• Tsunogai, U., Shingubara, R., Morishita, Y., Ito, M., Nakagawa, F., Yoshikawa, S., Utsugi, M., & Yokoo, A. (2022). Sampling volcanic plume using a drone-borne SelPS for remotely determined stable isotopic compositions of fumarolic carbon dioxide. Frontiers in Earth Science, 10, 833733. https://doi.org/10.3389/feart.2022.833733
• Witt, T., Walter, T. R., Müller, D., Guðmundsson, M. T., & Schöpa, A. (2018). The relationship between lava fountaining and vent morphology for the 2014–2015 Holuhraun eruption, Iceland, analyzed by video monitoring and topographic mapping. Frontiers in Earth Science, 6, 235. https://doi.org/10.3389/feart.2018.00235