A Novel UAV-Based Ultra-Light Weight Spectrometer for Field Spectroscopy

Burkart, Andreas; Cogliati, Sergio; Schickling, Anke; Rascher, Uwe

doi:10.1109/jsen.2013.2279720

Cited by 109 publications

(91 citation statements)

References 24 publications

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“…The second approach (ρ-spec) relies on a dual-spectrometer method [56,57] (Figure 5b). L (λ) measurements are recorded simultaneously by a second spectrometer operated at the ground over a typical Spectralon ® panel during HyUAS measurements.…”

Section: Retrieval Of Surface Reflectance and Fluorescencementioning

confidence: 99%

“…The second term represents the instruments transfer function derived as the ratio between simultaneous irradiance measurements collected by the two spectrometers at the moment of take-off. It must be remarked The second approach (ρ-spec) relies on a dual-spectrometer method [56,57] (Figure 5b). L inc (λ) measurements are recorded simultaneously by a second spectrometer operated at the ground over a typical Spectralon ® panel during HyUAS measurements.…”

Section: Retrieval Of Surface Reflectance and Fluorescencementioning

confidence: 99%

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Surface Reflectance and Sun-Induced Fluorescence Spectroscopy Measurements Using a Small Hyperspectral UAS

et al. 2017

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This study describes the development of a small hyperspectral Unmanned Aircraft System (HyUAS) for measuring Visible and Near-Infrared (VNIR) surface reflectance and sun-induced fluorescence, co-registered with high-resolution RGB imagery, to support field spectroscopy surveys and calibration and validation of remote sensing products. The system, namely HyUAS, is based on a multirotor platform equipped with a cost-effective payload composed of a VNIR non-imaging spectrometer and an RGB camera. The spectrometer is connected to a custom entrance optics receptor developed to tune the instrument field-of-view and to obtain systematic measurements of instrument dark-current. The geometric, radiometric and spectral characteristics of the instruments were characterized and calibrated through dedicated laboratory tests. The overall accuracy of HyUAS data was evaluated during a flight campaign in which surface reflectance was compared with ground-based reference measurements. HyUAS data were used to estimate spectral indices and far-red fluorescence for different land covers. RGB images were processed as a high-resolution 3D surface model using structure from motion algorithms. The spectral measurements were accurately geo-located and projected on the digital surface model. The overall results show that: (i) rigorous calibration enabled radiance and reflectance spectra from HyUAS with RRMSE < 10% compared with ground measurements; (ii) the low-flying UAS setup allows retrieving fluorescence in absolute units; (iii) the accurate geo-location of spectra on the digital surface model greatly improves the overall interpretation of reflectance and fluorescence data. In general, the HyUAS was demonstrated to be a reliable system for supporting high-resolution field spectroscopy surveys allowing one to collect systematic measurements at very detailed spatial resolution with a valuable potential for vegetation monitoring studies. Furthermore, it can be considered a useful tool for collecting spatially-distributed observations of reflectance and fluorescence that can be further used for calibration and validation activities of airborne and satellite optical images in the context of the upcoming FLEX mission and the VNIR spectral bands of optical Earth observation missions (i.e., Landsat, Sentinel-2 and Sentinel-3).

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Section: Retrieval Of Surface Reflectance and Fluorescencementioning

confidence: 99%

Section: Retrieval Of Surface Reflectance and Fluorescencementioning

confidence: 99%

Surface Reflectance and Sun-Induced Fluorescence Spectroscopy Measurements Using a Small Hyperspectral UAS

et al. 2017

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“…They showed that image quality can be improved through application of sensor correction techniques to facilitate subsequent image analysis. A novel, UAV-based lightweight highresolution spectrometer, which was tested in the field for the first time in the current study, was introduced by Burkart et al (2013). Nijland et al (2014) evaluated the use of nearinfrared (NIR) and RGB cameras for the use of vegetation monitoring and plant phenology trend detection and found that the NIR-converted cameras were outperformed by standard RGB cameras.…”

Section: S K Von Bueren Et Al: Deploying Four Optical Uav-based Sementioning

confidence: 99%

“…The spectrometer operated on an independent power source and its low weight and fine spectral resolution made it ideal for use on an UAV. The full specifications, calibration efforts and validation of the STS spectrometer are presented in Burkart et al (2013). An identical spectrometer, on the ground, acquired spectra of incoming radiance every time the airborne sensor was triggered.…”

Section: Uav Sensorsmentioning

confidence: 99%

Deploying four optical UAV-based sensors over grassland: challenges and limitations

Burkart²,

et al. 2015

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Abstract. Unmanned aerial vehicles (UAVs) equipped with lightweight spectral sensors facilitate non-destructive, nearreal-time vegetation analysis. In order to guarantee robust scientific analysis, data acquisition protocols and processing methodologies need to be developed and new sensors must be compared with state-of-the-art instruments. Four different types of optical UAV-based sensors (RGB camera, converted near-infrared camera, six-band multispectral camera and high spectral resolution spectrometer) were deployed and compared in order to evaluate their applicability for vegetation monitoring with a focus on precision agricultural applications. Data were collected in New Zealand over ryegrass pastures of various conditions and compared to ground spectral measurements. The UAV STS spectrometer and the multispectral camera MCA6 (Multiple Camera Array) were found to deliver spectral data that can match the spectral measurements of an ASD at ground level when compared over all waypoints (UAV STS: R 2 = 0.98; MCA6: R 2 = 0.92). Variability was highest in the near-infrared bands for both sensors while the band multispectral camera also overestimated the green peak reflectance. Reflectance factors derived from the RGB (R 2 = 0.63) and converted near-infrared (R 2 = 0.65) cameras resulted in lower accordance with reference measurements. The UAV spectrometer system is capable of providing narrow-band information for crop and pasture management. The six-band multispectral camera has the potential to be deployed to target specific broad wavebands if shortcomings in radiometric limitations can be addressed. Large-scale imaging of pasture variability can be achieved by either using a true colour or a modified near-infrared camera.Data quality from UAV-based sensors can only be assured, if field protocols are followed and environmental conditions allow for stable platform behaviour and illumination.

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“…Furthermore, the excessive energy consumption for the CCD cameras, especially for the cooling process, is usually not affordable by UAVs or spacebased vehicles/rovers. Finally, the weight of the spectrometer is also a problem (10)(11)(12).…”

mentioning

confidence: 99%

Lightweight Raman spectroscope using time-correlated photon-counting detection

Meng

Petrov

Cheng

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Raman spectroscopy is an important tool in understanding chemical components of various materials. However, the excessive weight and energy consumption of a conventional CCD-based Raman spectrometer forbids its applications under extreme conditions, including unmanned aircraft vehicles (UAVs) and Mars/Moon rovers. In this article, we present a highly sensitive, shot-noise-limited, and ruggedized Raman signal acquisition using a time-correlated photon-counting system. Compared with conventional Raman spectrometers, over 95% weight, 65% energy consumption, and 70% cost could be removed through this design. This technique allows space-and UAV-based Raman spectrometers to robustly perform hyperspectral Raman acquisitions without excessive energy consumption. Comparing with other molecular-specific imaging techniques, Raman spectroscopy provides a label-free contrast mechanism, which is intrinsically induced by the molecules contained in the sample. Relying on internal properties of molecules, investigators can avoid complicated sample preparation processes and molecular-specific labeling, etc. In many imaging/sensing applications, Raman spectroscopy often provides superior molecular specificity, imaging speed, and spectral resolution, and is usually considered as an emerging imaging technique (8, 9). However, despite decades of intensive study, Raman spectroscopy is still not widely applicable in space-based detection systems including unmanned aircraft vehicles (UAVs) and Mars/Moon rovers. This is mainly due to two hurdles: the unacceptable heavy weight of conventional spectrometers, and the excessive energy consumption by the entire system, especially the CCD camera.In typical laboratory-based Raman spectroscope setups, a beam of light is focused onto the sample. The scattered photons are then collected by a condenser lens and sent into a spectrometer. A diffractive grating is usually used to induce a spatial dispersion of the Raman peaks into different wavelengths. A CCD camera is used as the detector. In this sense, a correspondence between the CCD pixel and Raman shift can be established, and the Raman peaks are recognized and recorded.However, when extending this approach to field circumstances (e.g., space-based vehicles or UAVs), several key limitations emerge. First, due to the tiny angular dispersion provided by diffractive gratings, a long optical propagation length is required to create sufficient spatial dispersion. This is usually not allowed in space-based vehicles. Moreover, this long propagation length, together with any possible moving parts contained in the grating-based spectrometers, is unable to tolerate excessive vibrations during the launching/landing process of a space-based vehicle. Furthermore, the excessive energy consumption for the CCD cameras, especially for the cooling process, is usually not affordable by UAVs or spacebased vehicles/rovers. Finally, the weight of the spectrometer is also a problem (10-12).To overcome these difficulties, investigators invented and used several differe...

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A Novel UAV-Based Ultra-Light Weight Spectrometer for Field Spectroscopy

Cited by 109 publications

References 24 publications

Surface Reflectance and Sun-Induced Fluorescence Spectroscopy Measurements Using a Small Hyperspectral UAS

Surface Reflectance and Sun-Induced Fluorescence Spectroscopy Measurements Using a Small Hyperspectral UAS

Deploying four optical UAV-based sensors over grassland: challenges and limitations

Lightweight Raman spectroscope using time-correlated photon-counting detection

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