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First Measurements of Gas Flux with a Low-Cost Smartphone Sensor-Based UV Camera on the Volcanoes of Northern Chile
Remote Sensing ( IF 5 ) Pub Date : 2020-07-02 , DOI: 10.3390/rs12132122
Felipe Aguilera , Susana Layana , Felipe Rojas , Pilar Arratia , Thomas C. Wilkes , Cristóbal González , Manuel Inostroza , Andrew J.S. McGonigle , Tom D. Pering , Gabriel Ureta

UV cameras have been used for over a decade in order to remotely sense SO2 emission rates from active volcanoes, and to thereby enhance our understanding of processes related to active and passive degassing. Whilst SO2 column density retrievals can be more accurate/sophisticated using alternative techniques (e.g., Differential Optical Absorption Spectrometer (DOAS), Correlation Spectrometer (COSPEC)), due to their higher spectral resolutions, UV cameras provide the advantage of high time-resolution emission rates, a much greater spatial resolution, and the ability to simultaneously retrieve plume speeds. Nevertheless, the relatively high costs have limited their uptake to a limited number of research groups and volcanic observatories across the planet. One recent intervention in this regard has been the introduction of the PiCam UV camera, which has considerably lowered instrumental cost. Here we present the first data obtained with the PiCam system from seven persistently degassing volcanoes in northern Chile, demonstrating robust field operation in challenging conditions and over an extended period of time, hence adding credence to the potential of these units for more widespread dissemination to the international volcanic gas measurement community. Small and weak plumes, as well as strongly degassing plumes were measured at distances ranging 0.6–10.8 km from the sources, resulting in a wide range of SO2 emission rates, varying from 3.8 ± 1.8 to 361 ± 31.6 td−1. Our acquired data are discussed with reference to previously reported emission rates from other ground-based remotely sensed techniques at the same volcanoes, in particular considering: resolution of single plume emissions in multi-plume volcanoes, light dilution, plume geometry, seasonal effects, and the applied plume speed measurement methodology. The main internal/external factors that influence positive/negative PiCam measurements include camera shake, light dilution, and the performance of the OpenCV and control points post processing methods. A simple reprocessing method is presented in order to correct the camera shake. Finally, volcanoes were separated into two distinct groups: low and moderate SO2 emission rates systems. These groups correlate positively with their volcanological characteristics, especially with the fluid compositions from fumaroles.

中文翻译:

基于低成本智能手机传感器的紫外相机在智利北部火山上的气体通量首次测量

紫外线照相机已经使用了十多年,以便远程检测主动火山的SO 2排放速率,从而增强我们对与主动和被动脱气相关的过程的了解。虽然SO 2色谱柱密度的检索可以使用替代技术(例如,差分光学吸收光谱仪(DOAS),相关光谱仪(COSPEC))更准确/更复杂,因为它们具有更高的光谱分辨率,UV相机具有高时间分辨率发射率的优势,更大的空间分辨率,以及同时获取羽流速度的能力。然而,相对较高的成本将它们的使用限制在地球上有限的研究小组和火山观测站。最近在这方面的一项干预措施是引入了PiCam UV相机,该相机大大降低了仪器成本。在这里,我们展示了使用PiCam系统从智利北部七个持续脱气的火山中获得的第一批数据,证明了在挑战性条件下以及长时间内的强大野外操作能力,从而增强了这些装置在国际火山气测量界广泛传播的潜力。在距震源0.6-10.8 km的距离内测量了小而弱的羽状流以及强烈脱气的羽状流,导致了广泛的SO2排放速率,范围从3.8±1.8到361±31.6 td -1。我们将参考先前报告的来自同一地面火山的其他基于地面遥感技术的排放速率来讨论我们获取的数据,尤其要考虑:多峰火山中单羽排放的分辨率,光稀释,羽流几何形状,季节影响以及应用的羽流速度测量方法。影响PiCam正/负测量的主要内部/外部因素包括相机抖动,光线稀释以及OpenCV和控制点后处理方法的性能。为了纠正相机抖动,提出了一种简单的后处理方法。最后,将火山分为两个不同的组:低和中度SO 2排放率系统。这些基团与其火山学特征呈正相关,特别是与来自喷气孔的流体成分呈正相关。
更新日期:2020-07-02
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