Measurement of the LOFAR-HBA beam patterns using an unmanned aerial vehicle in the near field

Abstract. Methane emission fluxes from many facility-scale sources may be poorly quantified, potentially leading to uncertainties in the global methane budget. Accurate atmospheric measurement-based flux quantification is urgently required to address this. This paper describes the first test (using unbiased sampling) of a near-field Gaussian plume inversion (NGI) technique, suitable for facility-scale flux quantification, using a controlled release of methane gas. Two unmanned-aerial-vehicle (UAV) platforms were used to perform 22 flight surveys downwind of a point-source methane gas release from a regulated cylinder with a flowmeter. One UAV was tethered to an instrument on the ground, while the other UAV carried an on-board prototype instrument (both of which used the same near-infrared laser technology). Both instruments were calibrated using certified standards to account for variability in the instrumental gain factor, assuming fixed temperature and pressure. Furthermore, a water vapour correction factor, specifically calculated for the instrument, was applied and is described here in detail. We also provide guidance on potential systematic uncertainties associated with temperature and pressure, which may require further characterisation for improved measurement accuracy. The NGI technique was then used to derive emission fluxes for each UAV flight survey. We found good agreement of most NGI fluxes with the known controlled emission flux, within uncertainty, verifying the flux quantification methodology. The lower and upper NGI flux uncertainty bounds were, on average, 17 %±10(1σ) % and 227 %±98(1σ) % of the controlled emission flux, respectively. This range of conservative uncertainty bounds incorporate factors including the variability in the position of the time-invariant plume and potential for under-sampling. While these average uncertainties are large compared to methods such as tracer dispersion, we suggest that UAV sampling can be highly complementary to a toolkit of flux quantification approaches and may be a valuable alternative in situations where site access for tracer release is problematic. We see tracer release combined with UAV sampling as an effective approach in future flux quantification studies. Successful flux quantification using the UAV sampling methodology described here demonstrates its future utility in identifying and quantifying emissions from methane sources such as oil and gas extraction infrastructure facilities, livestock agriculture, and landfill sites, where site access may be difficult.

Download Full-text

Methane emission detection and flux quantification from exploratory hydraulic fracturing in the United Kingdom, using unmanned aerial vehicle sampling

10.5194/egusphere-egu2020-16797 ◽

2020 ◽

Author(s):

Adil Shah ◽

Hugo Ricketts ◽

Joseph Pitt ◽

Jacob Shaw ◽

Khristopher Kabbabe ◽

...

Keyword(s):

United Kingdom ◽

Unmanned Aerial Vehicle ◽

Gas Flow ◽

Near Infrared ◽

Near Field ◽

Air Inlet ◽

The United Kingdom ◽

Aerial Vehicle ◽

Flux Quantification ◽

Intermittent Sampling

<p>Unmanned aerial vehicle (UAV) sampling was used to derive high-precision methane mole fraction measurements downwind of the United Kingdom&#8217;s first onshore exploratory operation to horizontally hydraulically fracture shale rock. Sampling took place using two UAVs on five intermittent sampling days between October 2018 and February 2019. One UAV carried an on-board prototype sensor while the other was connected to a sensor on the ground, using a tethered air inlet. Both instruments used near infrared spectroscopy. Methane emissions were observed on one sampling day (14<sup>th</sup> January 2019) over a 1.4-hour sampling window, due to cold venting of methane following a nitrogen lift. The nitrogen lift procedure was used to induce gas flow during liquid unloading. The near-field Gaussian plume inversion flux quantification method was used to derive four instantaneous flux ranges (within uncertainty) from the four UAV flight surveys conducted during the emission window.</p>

Download Full-text

A Near-Field Gaussian Plume Inversion Flux Quantification Method, Applied to Unmanned Aerial Vehicle Sampling

Atmosphere ◽

10.3390/atmos10070396 ◽

2019 ◽

Vol 10 (7) ◽

pp. 396 ◽

Cited By ~ 8

Author(s):

Adil Shah ◽

Grant Allen ◽

Joseph R. Pitt ◽

Hugo Ricketts ◽

Paul I. Williams ◽

...

Keyword(s):

Unmanned Aerial Vehicle ◽

Near Field ◽

Methane Emissions ◽

Point Sources ◽

Flux Analysis ◽

Maximum Height ◽

Spatial Dimensions ◽

Aerial Vehicle ◽

Specific Source ◽

Gaussian Plume

The accurate quantification of methane emissions from point sources is required to better quantify emissions for sector-specific reporting and inventory validation. An unmanned aerial vehicle (UAV) serves as a platform to sample plumes near to source. This paper describes a near-field Gaussian plume inversion (NGI) flux technique, adapted for downwind sampling of turbulent plumes, by fitting a plume model to measured flux density in three spatial dimensions. The method was refined and tested using sample data acquired from eight UAV flights, which measured a controlled release of methane gas. Sampling was conducted to a maximum height of 31 m (i.e. above the maximum height of the emission plumes). The method applies a flux inversion to plumes sampled near point sources. To test the method, a series of random walk sampling simulations were used to derive an NGI upper uncertainty bound by quantifying systematic flux bias due to a limited spatial sampling extent typical for short-duration small UAV flights (less than 30 min). The development of the NGI method enables its future use to quantify methane emissions for point sources, facilitating future assessments of emissions from specific source-types and source areas. This allows for atmospheric measurement-based fluxes to be derived using downwind UAV sampling for relatively rapid flux analysis, without the need for access to difficult-to-reach areas.

Download Full-text

Supplementary material to "Testing the near-field Gaussian plume inversion flux quantification technique using unmanned aerial vehicle sampling"

10.5194/amt-2019-289-supplement ◽

2019 ◽

Author(s):

Adil Shah ◽

Joseph R. Pitt ◽

Hugo Ricketts ◽

J. Brain Leen ◽

Paul I. Williams ◽

...

Keyword(s):

Unmanned Aerial Vehicle ◽

Near Field ◽

Aerial Vehicle ◽

Gaussian Plume ◽

Flux Quantification ◽

Supplementary Material

Download Full-text

Testing the near-field Gaussian plume inversion flux quantification technique using unmanned aerial vehicle sampling

10.5194/amt-2019-289 ◽

2019 ◽

Cited By ~ 2

Author(s):

Adil Shah ◽

Joseph R. Pitt ◽

Hugo Ricketts ◽

J. Brain Leen ◽

Paul I. Williams ◽

...

Keyword(s):

Unmanned Aerial Vehicle ◽

Near Field ◽

Emission Flux ◽

Methane Gas ◽

Uncertainty Bound ◽

Emission Fluxes ◽

Site Access ◽

Aerial Vehicle ◽

Gaussian Plume ◽

Flux Quantification

Abstract. Methane emission fluxes from facility-scale sources may be poorly quantified, leading to uncertainties in the global methane budget. Accurate atmospheric measurement based flux quantification is urgently required to address this. This paper describes the test of a new near-field Gaussian plume inversion (NGI) technique, suitable for facility-scale flux quantification, using a controlled release of methane gas. Two unmanned aerial vehicle (UAV) platforms were used to perform 22 flight surveys downwind of a point-source release of methane gas from a regulated and flow-metered cylinder. One UAV was tethered to an instrument on the ground, while the other UAV carried an on-board high-precision prototype instrument, both of which used the same near-infrared laser technology. The performance of these instruments from UAV sampling is described. Both instruments were calibrated using certified standards, to account for variability in the instrumental gain factor. Furthermore, a modified approach to correcting for the effect of water vapour applied and is described here in detail. The NGI technique was used to derive emission fluxes for each UAV flight survey. We found good agreement of most NGI fluxes with the known controlled emission flux, within uncertainty, verifying the flux quantification methodology. The lower NGI flux uncertainty bound was, on average, 17 % ± 10(1σ) % of the controlled emission flux and the upper NGI flux uncertainty bound was, on average, 218 % ± 100(1σ) % of the controlled emission flux. These highly conservative uncertainty ranges incorporate factors including the variability in the position of the plume and the potential for under-sampling. While these average uncertainties are large compared to methods such as tracer dispersion, we suggest that UAV sampling can be highly complementary to a toolkit of flux approaches and may perform well in situations where site access for tracer release is problematic. We see tracer release applied to UAV sampling as an effective combination in future flux quantification studies. Successful flux quantification using this UAV sampling methodology demonstrates its future utility in identifying and quantifying emissions from methane sources such as oil and gas infrastructure facilities, livestock agriculture and landfill sites, where site access may be difficult.

Download Full-text

Cooperative Navigation between a Ground Vehicle and an Unmanned Aerial Vehicle in GNSS-Challenged Environments

Proceedings of the 29th International Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+ 2016) ◽

10.33012/2016.14623 ◽

2016 ◽

Author(s):

Victor O. Sivaneri ◽

Jason N. Gross

Keyword(s):

Unmanned Aerial Vehicle ◽

Ground Vehicle ◽

Cooperative Navigation ◽

Aerial Vehicle

Download Full-text

Study on Fault Diagnosis of Planetary Gearbox in Unmanned Aerial Vehicle Using Multi sensor Data

Journal of Applied Reliability ◽

10.33162/jar.2020.12.20.4.332 ◽

2020 ◽

Vol 20 (4) ◽

pp. 332-342

Author(s):

Hyung Jun Park ◽

Seong Hee Cho ◽

Kyung-Hwan Jang ◽

Jin-Woon Seol ◽

Byung-Gi Kwon ◽

...

Keyword(s):

Fault Diagnosis ◽

Unmanned Aerial Vehicle ◽

Sensor Data ◽

Planetary Gearbox ◽

Aerial Vehicle

Download Full-text

Results of Spatial Structure of Atmosphere Radiation in a Spectral Range (1.5–2) µm Research

Light & Engineering ◽

10.33383/2017-061 ◽

2018 ◽

pp. 7-13

Author(s):

Anton M. Mishchenko ◽

Sergei S. Rachkovsky ◽

Vladimir A. Smolin ◽

Igor V . Yakimenko

Keyword(s):

Spatial Structure ◽

Unmanned Aerial Vehicle ◽

Wavelength Range ◽

Spectral Range ◽

Near Ir ◽

Optoelectronic Systems ◽

Aerial Vehicle

Results of experimental studying radiation spatial structure of atmosphere background nonuniformities and of an unmanned aerial vehicle being the detection object are presented. The question on a possibility of its detection using optoelectronic systems against the background of a cloudy field in the near IR wavelength range is also considered.

Download Full-text