To better assess the danger posed by volcanoes, researchers at the Technical University of Munich (TUM) have developed a new measurement system. Laser beams are sent through escaping gas clouds and reflected by drones. An algorithm uses the reflected signals to generate a map showing gas concentrations, including elevated carbon dioxide levels. The ratio of carbon dioxide to sulfur dioxide is an important indicator of impending eruptions.
Andreas Schmitz / TUM The more forcefully lava rises from the Earth's interior toward the surface, the more gases are released. Carbon and sulfur compounds are good indicators of current activity in a volcanic field. In particular, the ratio of carbon dioxide to sulfur dioxide provides insight into what is happening beneath the Earth's surface. Until now, these measurements had to be taken from ground level. The drawback is that the gases measured there do not originate solely from volcanic activity but are also emitted by surrounding vegetation and soil.
To minimize these background signals, drones are now being used to fly above the gas clouds. "This is more precise and safer," says Prof. Achim Lilienthal, deputy director of the TUM MIRMI Robotics Institute and head of the Chair of Perception for Intelligent Systems at the TUM School of Computation, Information, and Technology.
Autonomous measurement of gases over a volcanic field
As part of the DFG research project "Measurement Technology on Flying Platforms," his research team has now developed a system capable of determining gas concentrations over an active volcanic field with high precision. TUM researcher Marius Schaab has now deployed the system autonomously for the first time on the Aeolian island of Vulcano, off the coast of Sicily. He has mounted a laser on a small cart that automatically locates an airborne drone and aligns itself with a reflector on the drone. The reflected beam is slightly weakened as it passes through the gas cloud because it is absorbed by the gas being measured - in this case, carbon dioxide.
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Algorithm calculates tomographic map of gas concentrations
As the drone flies a pre-determined route for 10 to 15 minutes up to 60 meters away from the laser, the system takes up to 3,000 measurements. An algorithm converts the data into a map showing the distribution of gas concentrations at a given altitude. To do this, the researchers also take into account the local wind conditions. Previous wind tunnel research showed that this method is highly accurate, with a measurement error of about 5%.
"Our goal is to automate the measurement and mapping processes and have artificial intelligence interpret the data," says Lilienthal, who has spent many years researching robots' sense of smell and is now, for the first time, using a drone-based autonomous detection system to monitor volcanic fields.
Other Measurement Principles Used by Researchers in Mainz
Unlike the TUM team, Prof. Thorsten Hoffmann of Johannes Gutenberg University Mainz uses onboard sensors in his drones to measure chemical concentrations in the air. In photometric measurement cells, light of a specific wavelength is absorbed to determine the concentration of a gas. The electrochemical approach, on the other hand, is based on redox reactions at the electrode surface.
"Carbon dioxide and sulfur dioxide are particularly important to us, because their ratio provides insight into what is happening underground. The solubility of these gases in magma depends, among other things, on pressure and therefore changes with depth. As a result, the composition of the escaping gas mixture provides clues about the processes within the volcanic system," says the chemist. "We fly directly into the volcanic plume, which allows us to determine the gas concentrations along the flight path."
The ratio of carbon dioxide to sulfur dioxide is a reliable indicator of an impending eruption
In addition to geophysical and temperature measurements, volcanic gases are another important indicator for assessing the danger posed by a volcano. Research conducted on Mount Etna in Sicily, the neighboring Aeolian Islands, and the Phlegraean Fields near Naples shows that each volcanic area has its own characteristic gas signature. Shortly before an eruption, the composition of gases emitted from fumaroles and volcanic plumes often changes significantly. Volcanologist Nicole Bobrowski of Heidelberg University explains: "For example, the ratio of carbon dioxide to sulfur dioxide initially rises sharply and then falls again before the eruption begins."
Andreas Schmitz / TUM 
Andreas Schmitz / TUM 
Andreas Schmitz / TUM 
Andreas Schmitz / TUM 
Andreas Schmitz / TUM 
Andreas Schmitz / TUM Andreas Schmitz / TUM Methane Release Rate Estimation Using Model-Based Gas Tomography; Marius Schaab, Thomas Wiedemann, Patrick Hinsen, Achim J. Lilienthal; IEEE Sensors Letters, 9-2025; https://ieeexplore.ieee.org/document/11123752
Visual Cooperative Drone Tracking for Open-Path Gas Measurements; Marius Schaab , Alisha Kiefer , Thomas Wiedemann , Patrick Hinsen , Achim J. Lilienthal ; https://www.researchgate.net/publication/401178423_Visual_Cooperative_Drone_Tracking_for_Open-Path_Gas_Measurements (vorgestellt auf der I2MTC 2026, Nancy)
Towards Drone-based Mapping of Volcanic Gases using Gas Tomography; Marius Schaab , Niklas Karbach , Antonia Rabe , Thomas Wiedemann , Patrick Hinsen , Dmitriy Shutin , Thorsten Hoffmann , Achim J. Lilienthal ; https://arxiv.org/abs/2605.27180 (vorgestellt auf der ISOEN 2026 in Chongqing)
- TUM Professor Achim Lilienthal has been conducting research on robots' sense of smell for many years. Before joining TUM four years ago, the robotics expert had already developed robots capable of detecting methane, carbon dioxide and toxic gases. In a mine in Kiruna, Sweden, he deployed sensors that detected when batteries in electrically powered mining equipment began overheating or even caught fire. He uses his "Gasbots" to create gas concentration maps from surface measurements to locate areas where methane is escaping. See: www.mirmi.tum.de/mirmi/aktuelles/education/article/riechende-roboter-einer-der-weltweit-fuehrenden-wissenschaftler-wechselt-zur-tum/
- The Munich Institute of Robotics and Machine Intelligence (TUM MIRMI) is an integrated research institute at the Technical University of Munich (TUM) focused on robotics and AI. TUM MIRMI brings together leading expertise in key areas of robotics, including perception and data science. Nearly 80 TUM professorships collaborate within TUM MIRMI to develop innovative robotic and AI-supported solutions for the environment, health, mobility, work, and, not least, security and defense. Prof. Lorenzo Masia heads TUM MIRMI. More information:
