Optical gas imaging detects invisible methane leaks in the air by using laser-based sensors tuned to the specific infrared wavelengths at which methane absorbs light. When the laser beam passes through a plume of escaping gas, the absorption signature is measured and converted into a quantified leak indication. This makes airborne optical gas imaging far more sensitive and objective than traditional handheld cameras or ground-based surveys.
The technology is particularly relevant in 2026, as operators of gas pipelines, landfills, and other methane-emitting infrastructure face binding obligations under the EU Methane Regulation to regularly measure methane emissions and report findings to regulators. The sections below unpack the key questions operators and inspection professionals most often ask about how aerial optical gas imaging actually works.
What wavelengths does optical gas imaging use to spot methane?
Airborne optical gas imaging systems detect methane by targeting the mid-infrared spectral range, specifically around 3.3 micrometres, where methane molecules absorb light most strongly. This absorption band is highly specific to CH4, meaning the sensor can distinguish methane from other gases present in the atmosphere with a high degree of confidence.
The choice of wavelength is not arbitrary. Every chemical compound absorbs electromagnetic radiation at characteristic wavelengths determined by its molecular structure. Methane has a particularly strong and well-defined absorption feature in the mid-infrared, which is why laser systems tuned to this region can detect even trace concentrations. By measuring how much laser energy is absorbed along the beam path, the sensor can infer the presence and concentration of methane below the aircraft.
This spectral selectivity is one of the key advantages of laser-based airborne systems over broadband thermal cameras. A standard infrared camera captures heat contrast and can visualise gas clouds, but it cannot easily distinguish methane from other hydrocarbons or quantify the leak rate. A spectrally targeted laser system, by contrast, measures a physical property unique to methane, which makes the results both more specific and more quantifiable.
How does the DIAL method differ from standard OGI cameras?
The Differential Absorption LIDAR (DIAL) method differs from standard optical gas imaging cameras by actively emitting two laser pulses at different wavelengths and comparing how much each is absorbed along the measurement path. One pulse is tuned to a wavelength methane absorbs strongly; the other is tuned to a nearby wavelength methane barely absorbs. The difference in return signal between the two pulses is directly proportional to the methane column concentration in the beam path.
Standard OGI cameras are passive instruments. They detect the thermal contrast between a gas cloud and its background, making gas clouds visible as a visual plume on a screen. This approach is useful for rapid visual surveys at close range but has meaningful limitations: results depend on background temperature contrast, wind conditions, and operator interpretation. Quantifying the actual leak rate from a passive camera image requires additional assumptions and modelling.
DIAL, by contrast, is an active measurement technique. The system generates its own light source, measures the physical absorption of that light by methane molecules, and computes a column-integrated concentration directly from the physics of the interaction. This makes DIAL measurements objective, reproducible, and quantifiable rather than dependent on visual contrast or operator judgement. For operators who need to measure methane emissions to a regulatory standard, this distinction is significant.
How sensitive is airborne optical gas imaging at detecting small leaks?
The sensitivity of airborne optical gas imaging using the DIAL method is high enough to detect leaks as small as 150 litres per hour under wind speeds of up to 24 km/h, even at survey altitudes of 100 to 150 metres and flight speeds of up to 180 km/h. This sensitivity is achieved through a high measurement rate of 1,000 measurement points per second, which ensures dense spatial coverage even at speed.
To put this in practical context, a leak of 150 litres per hour is a very small fugitive emission. Many pipeline leaks that would go undetected during routine ground inspections fall within this range. The ability to detect such small leaks from a fast-moving helicopter dramatically increases the efficiency of inspection programmes compared to walking surveys or vehicle-based methods, particularly across long-distance transmission pipelines.
Sensitivity is also influenced by atmospheric conditions. Wind disperses gas plumes, which reduces peak concentration and can make small leaks harder to detect. The wind speed threshold of 24 km/h reflects the point at which dispersion begins to reduce detection reliability at the stated sensitivity level. In calmer conditions, even smaller leaks may be detectable. Operators planning surveys should factor in seasonal and local wind patterns when scheduling inspections to maximise detection performance.
What types of methane sources can aerial OGI survey?
Airborne optical gas imaging can survey a wide range of methane-emitting sources, including transmission and distribution gas pipelines, compressor stations, LNG terminals, underground gas storage sites, landfills, and coal mine ventilation shafts. Any site or linear infrastructure where fugitive methane emissions may occur is a candidate for aerial survey.
The flexibility of airborne surveys is one of their most practical advantages. A helicopter-based system can cover hundreds of kilometres of pipeline in a single day, transition from linear infrastructure to area sources such as a landfill or storage facility within the same flight, and access terrain that would be difficult or time-consuming to survey on foot or by vehicle. This makes aerial OGI well suited to both routine compliance surveys and targeted investigations following an incident or reported concern.
For area sources such as landfills, the DIAL method can also be used to quantify total site-level emissions rather than simply locating individual leak points. By flying a defined pattern over the site and measuring methane concentrations at multiple altitudes and positions, it is possible to derive a site-level emission flux. This type of methane emission quantification is increasingly required under emissions reporting frameworks, making it a core part of what aerial inspection services now need to deliver.
Does airborne methane detection meet EU Methane Regulation requirements?
Yes, airborne methane detection using high-sensitivity laser systems can meet the requirements of the EU Methane Regulation 2024/1787, which requires fossil energy infrastructure operators to regularly measure methane emissions, detect and repair leaks, and report quantified emissions annually. The regulation distinguishes between component-level leak detection and site-level emission quantification, and aerial DIAL technology addresses both.
The EU Methane Regulation sets specific requirements for what are referred to as Type 2 surveys, which cover underground equipment and require higher sensitivity than standard optical gas imaging cameras can reliably provide. Airborne DIAL systems that meet the sensitivity thresholds specified in the regulation are able to fulfil this requirement, which is why regulatory approval is an important criterion when selecting an inspection provider.
Beyond detection, the regulation also requires that operators quantify methane emission factors at the source and site levels and have those measurements verified by independent third parties. Airborne survey methods that produce quantified, georeferenced results with documented measurement parameters are well positioned to support this verification process. Operators who rely on visual OGI cameras alone may find it harder to demonstrate compliance with the quantification requirements, since those instruments are not inherently designed to produce the numerical emission data the regulation demands.
For operators looking to understand their obligations in more detail, the regulatory landscape around methane is evolving quickly, and the technical standards supporting the regulation are being developed in parallel with enforcement timelines.
How are airborne methane survey results reported to operators?
Airborne methane survey results are typically delivered through a secure web-based GIS platform that allows operators to view georeferenced leak indications, emission quantification data, and flight track information on both desktop and mobile devices. Each detected gas indication is tagged with its location, estimated leak rate, and the measurement parameters recorded at the time of detection.
This format is designed to make survey results immediately actionable. A grid operator can log into the platform after a survey, identify which pipeline sections showed indications, prioritise repairs based on estimated leak severity, and assign field teams to specific locations using the map interface. The ability to access results on mobile devices is particularly useful for field crews who need to navigate to a leak location and verify conditions on the ground.
Reporting packages typically also include summary documentation suitable for regulatory submission, covering total survey length, detection statistics, measurement conditions, and emission estimates where site-level quantification was performed. This documentation supports the annual reporting obligations that operators face under frameworks such as the EU Methane Regulation, where both the detection results and the methodology used to obtain them must be recorded and made available to verifiers.
How ADLARES helps operators detect and report methane emissions
We provide a complete airborne methane inspection service built around our CHARM® technology, the world’s only DVGW-approved gas remote detection system. Our service is designed specifically to help operators of pipelines, landfills, storage sites, and other gas infrastructure meet their obligations to measure methane emissions, locate leaks, and report quantified findings under the EU Methane Regulation and other applicable frameworks.
Here is what we deliver:
- High-sensitivity aerial leak detection using the DIAL method, capable of detecting leaks from 150 l/h at survey speeds of up to 180 km/h
- Site-level methane emission quantification (LDAQ) for landfills, compressor stations, storage facilities, and other area sources, producing the emission factor data regulators require
- EU Methane Regulation Type 2 compliance, with sensitivity levels and methodology that meet the regulatory standard for underground equipment surveys
- Georeferenced results delivered via a secure Web GIS platform, accessible on desktop and mobile, enabling rapid field verification and repair prioritisation
- Regulatory-grade reporting documentation suitable for third-party verification and annual emissions reporting submissions
- Extensive operational track record, with over 250,000 km of gas pipelines inspected across Europe since 2008
If you operate gas infrastructure and need a reliable, approved method to detect leaks and quantify your methane emissions, we are ready to help. Contact our team to discuss your inspection requirements and find out how we can support your compliance programme.