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From a clear image of the upper cone (a), we extracted the outline of the volcano and used it to recognize the volcano in each captured image. Panel (b) shows the mask used in the normed 2D cross-correlation algorithm that determines whether or not the volcano appears in each new captured image. The colour scale in panel (a) represents the temperature and the grayscale in panel (b) represents the weight (importance) of the template pixels. In each captured image (c,e), the volcano recognition algorithm obtains the contours (d,f) and cross-correlates them with the masked template (b). The solid-line squares show the position of the volcano found. The normalised cross-correlation coefficient, the quality, the location of the crater as a row-column pair from the lower left corner, and the result of the recognition are shown for an image of the Reventador volcano in August 2021 (c,d) and in October 2021 (e,f), after the camera was moved slightly downwards. The algorithm is independent of the displacement of the cone within the image. The quality factor is calculated from the number of features (contours) and the range of temperature inside the dashed-line square.
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The monitoring of the frequency, intensity/magnitude and dynamics of explosive events at volcanoes in a state of unrest is key to surveying and forecasting their activity. Thermal and visual video observations of eruptive phenomena, and their correlation with data from deformation and seismic networks, are often limited by technical constraints inc...
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... volcanoes such as Reventador, located in the sub-Andean region where the Amazonian Forest environment is very humid, the periods in which the volcano is clear from cloud cover can be as small as ten hours in a week. In order to optimize the amount of disk space and transmission bandwidth, VIGIA counts with an algorithm to recognize whether the volcano is clear or clouded ( Figure 5). This algorithm uses the contours of the crater in good conditions (i.e., no clouds or gas in the surroundings) as a template that the computer searches for in each picture (Figure 5a). ...
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... order to optimize the amount of disk space and transmission bandwidth, VIGIA counts with an algorithm to recognize whether the volcano is clear or clouded ( Figure 5). This algorithm uses the contours of the crater in good conditions (i.e., no clouds or gas in the surroundings) as a template that the computer searches for in each picture (Figure 5a). The algorithm also uses a weighted mask to enhance the importance of the flanks of the volcano over the upper rim (Figure 5b). ...
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... algorithm uses the contours of the crater in good conditions (i.e., no clouds or gas in the surroundings) as a template that the computer searches for in each picture (Figure 5a). The algorithm also uses a weighted mask to enhance the importance of the flanks of the volcano over the upper rim (Figure 5b). The mask was defined based on the rapid changes of the morphology observed at the upper rim [58]. ...
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... applied a normalised 2D cross-correlation algorithm included in OpenCV API to search for the template and locate the point with the highest correlation coefficient between the image and the template. As a result of this operation, we have the normalised the cross-correlation coefficient and the location of the pattern in row and column coordinates from the origin; in the particular case shown in Figure 5, from the lower left corner. We used this coefficient to discriminate if the volcano appears in the image by simply comparing it to a predefined threshold; if the volcano is clouded, the coefficient is very low, and the location is reported as the origin. ...
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... Camera-generated proximal thermal infrared (TIR) observations are widely used to monitor and study volcanoes, and several studies have reported the use of TIR observations to follow evolutions of volcanic activity and to map distributions of volcanic products [50][51][52][53][54][55][56][57][58]. In contrast, very few volcanic areas are currently being monitored with permanent, ground, proximal networks of TIR cameras during non-eruptive periods to detect surface temperature variations as indicators of possible changes in the volcanic system [59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76]. ...
Thermal infrared (TIR) time series images acquired by ground, proximal TIR stations provide valuable data to study evolution of surface temperature fields of diffuse degassing volcanic areas. This paper presents data processing results related to TIR images acquired since 2004 by six ground stations in the permanent thermal infrared surveillance network at Campi Flegrei (TIRNet) set up by INGV-Osservatorio Vesuviano. These results are reported as surface temperature and heat flux time series. The processing methodologies, also discussed in this paper, allow for presentation of the raw TIR image data in a more comprehensible form, suitable for comparisons with other geophysical parameters. A preliminary comparison between different trends in the surface temperature and heat flux values recorded by the TIRNet stations provides evidence of peculiar changes corresponding to periods of intense seismicity at the Campi Flegrei caldera. During periods characterized by modest seismicity, no remarkable evidence of common temperature variations was recorded by the different TIRNet stations. Conversely, almost all the TIRNet stations exhibited common temperature variations, even on a small scale, during periods of significant seismic activity. The comparison between the seismicity and the variations in the surface temperature and heat flux trends suggests an increase in efficiency of heat transfer between the magmatic system and the surface when an increase in seismic activity was registered. This evidence recommends a deeper, multidisciplinary study of this correlation to improve understanding of the volcanic processes affecting the Campi Flegrei caldera.
... Thermal infrared (IR) remote sensing is a passive technique to measure the temperatures of objects within the field of view of an optical imaging system at some distance from the scene. The amount of radiation that objects emit and absorb at thermal infrared wavelengths (8)(9)(10)(11)(12)(13)(14) µm) depends on their temperature and emissivity, which depends on wavelength. The energy of the emitted photons can be collected using a suitable wavelength-dependent detector, optical imaging system and digital electronics. ...
... Prior work on this topic has been hindered by the availability of cost-effective systems with sufficient accuracy and ease of use. With the widespread availability of uncooled thermal cameras, increasingly, camera systems are being deployed and used at volcanoes [6][7][8][9][10][11][12][13]. Patrick et al. [7] used a FLIR camera to characterise volcanic activity at Stromboli, Italy. ...
... The use of infrared cameras at volcanoes is not widespread, but several field studies have been undertaken using handheld, commercial infrared cameras, e.g., [6,8,9,12,13]. In many cases where they are used, they tend to provide real-time infrared imagery of a mostly qualitative nature with a temperature scale showing scene temperatures. ...
Ground-based infrared cameras can be used effectively and safely to provide quantitative information about small to moderate-sized volcanic eruptions. This study describes an infrared camera that has been used to measure emissions from the Mt. Etna and Stromboli (Sicily, Italy) volcanoes. The camera provides calibrated brightness temperature images in a broadband (8–14 µm) channel that is used to determine height, plume ascent rate and volcanic cloud/plume temperature and emissivity at temporal sampling rates of up to 1 Hz. The camera can be operated in the field using a portable battery and includes a microprocessor, data storage and WiFi. The processing and analyses of the data are described with examples from the field experiments. The updraft speeds of the small eruptions at Stromboli are found to decay with a timescale of ∼10 min and the volcanic plumes reach thermal equilibrium within ∼2 min. A strong eruption of Mt. Etna on 1 April 2021 was found to reach ∼9 km, with ascent speeds of 10–20 ms⁻¹. The plume, mostly composed of the gases CO2, water vapour and SO2, became bent over by the prevailing winds at high levels, demonstrating the need for multiple cameras to accurately infer plume heights.
... Identification of the morphological changes of a volcano's surface can be achieved through regular observations using visual and thermal images (Spampinato et al., 2011;Mania et al., 2019). Direct observations of superficial activity at active volcanoes represent a fundamental tool in volcano monitoring (Spampinato et al., 2011;Vásconez et al., 2022a). These observations contribute to our understanding of volcanic processes occurring during an eruption and are critical in quantifying the distribution and volume of deposits, as well as changes in eruptive dynamics. ...
Shifts in activity at long-active, open-vent volcanoes are difficult to forecast because precursory signals are enigmatic and can be lost in and amongst daily activity. Here, we propose that crater and vent morphologies, along with summit height, can help us bring some insights into future activity at one of Ecuador’s most active volcanoes El Reventador. On 3 November 2002, El Reventador volcano experienced the largest eruption in Ecuador in the last 140 years and has been continuously active ever since with transitions between and coexistence of explosive and effusive activity, characterized by Strombolian and Vulcanian behavior. Based on the analysis of a large dataset of thermal and visual images, we determined that in the last 20 years of activity, the volcano faced three destructive events: A. Destruction of the upper part of the summit leaving a north-south breached crater (3 November 2002), B. NE border crater collapse (2017), and C. NW flank collapse (2018), with two periods of reconstruction of the edifice: Period 1. Refill of the crater (2002-early 2018) and Period 2. Refill of the 2018 scar (April 2018–December 2022). Through photogrammetric analysis of visual and thermal images acquired in 11 overflights of the volcano, we created a time-series of digital elevation models (DEMs) to determine the maximum height of the volcano at each date, quantify the volume changes between successive dates, and characterize the morphological changes in the summit region. We estimate that approximately 34.1x10⁶ m³ of volcanic material was removed from the volcano due to destructive events, whereas 64.1x10⁶ m³ was added by constructive processes. The pre-2002 summit height was 3,560 m and due to the 2002 eruption it decreased to 3,527 m; it regained its previous height between 2014 and 2015 and the summit crater was completely filled by early April 2018. Event A resulted from an intrusion of magma that erupted violently; we proposed that Events B and C could be a result of an intrusion as well but may also be due to a lack of stability of the volcano summit which occurs when it reaches its maximum height of approximately 3,590 and 3,600 m.
... Eruptive activity continues until the present day and is characterized by gas and ash emissions and explosions, lava flows, and small PDCs (Fig. 6d-f) (Samaniego et al. 2008a, b;Naranjo et al. 2016;Arnold et al. 2017;Vásconez et al. 2022b). The volcanic cone has suffered drastic morphological changes during these two decades of activity (Almeida et al. 2019). ...
The Instituto Geofísico (IG-EPN) was created in 1983 by faculty of the Escuela Politécnica Nacional, a public university in Quito, Ecuador, with the objective of assessing volcanic hazard in the country. Since then, the IG-EPN has established and developed an instrumental monitoring network and from 1999 has faced the eruption of five continental-arc volcanoes (Guagua Pichincha, Tungurahua, Reventador, Cotopaxi, and Sangay) which displayed varied hazards, eruptive dynamics, eruption durations, and socio-economic contexts. At the same time, mainly effusive eruptions took place in Galápagos archipelago, which has undergone an increase in local population over the last two decades and hence in the risk posed by volcanic eruptions. The outstanding handling of these volcanic crises was the reason why IG-EPN was granted with the 2020 Volcanic Surveillance and Crisis Management IAVCEI Award. Now, the IG-EPN manages a country-wide network of about 500 instruments to monitor both volcanic and tectonic activity with a highly qualified staff of 80 people. This manuscript describes the history of IG-EPN, the main volcanic hazard studies and resulting hazard maps; the instrumental networks; and the volcanic crises that the IG-EPN faced during the last forty years.
... The detection of the thermal anomaly and the growth of its area may indicate the intensification of volcano activity and/or the possible beginning of its eruption. As one of the main methods of operational monitoring in volcanoes, systems created with video cameras are widely used [1][2][3][4][5][6][7][8][9]. Unlike most modern satellite observation systems, they allow us to monitor the state of dangerous natural objects in real-time with a higher frequency and resolution. ...
One of the most important tasks when studying volcanic activity is to monitor their thermal radiation. To fix and assess the evolution of thermal anomalies in areas of volcanoes, specialized hardware-thermal imagers are usually used, as well as specialized instruments of modern satellite systems. The data obtained with their help contain information that makes it relatively easy to track changes in temperature and the size of a thermal anomaly. At the same time, due to the high cost of such complexes and other limitations, thermal imagers sometimes cannot be used to solve scientific problems related to the study of volcanoes. In the current paper, day/night video cameras with an infrared-cut filter are considered as an alternative to specialized tools for monitoring volcanoes’ thermal activity. In the daytime, a camera operated in the visible range, and at night the filter was removed, increasing the camera’s light sensitivity by allowing near-infrared light to hit the sensor. In that mode, a visible thermal anomaly could be registered on images, as well as other bright glows, flares, and other artifacts. The purpose of this study is to detect thermal anomalies on night images, separate them from other bright areas, and find their characteristics, which could be used for volcano activity monitoring. Using the image archive of the Sheveluch volcano as an example, this article presents the results of developing a computer algorithm that makes it possible to find and classify thermal anomalies on video frames with an accuracy of 98%. The test results are presented, along with their validation based on thermal activity data obtained from satellite systems.
... Multiple volcanic hazards are associated with tephra dispersal [1][2][3], which encourages volcanological observatories to permanently improve their monitoring systems with the aim of tracking the main features of an explosive eruption [4][5][6][7]. Eruption column height is one of the most important source parameters for volcanic monitoring purposes [8,9]. In fact, this parameter is reported in the VONA (Volcano Observatory Notices for Aviation) messages issued in real-time by volcano observatories when an ash-producing event occurs and/or when there is a change in volcanic behavior [10]. ...
Volcanic plume height is one the most important features of explosive activity; thus, it is a parameter of interest for volcanic monitoring that can be retrieved using different remote sensing techniques. Among them, calibrated visible cameras have demonstrated to be a promising alternative during daylight hours, mainly due to their low cost and low uncertainty in the results. However, currently these measurements are generally not fully automatic. In this paper, we present a new, interactive, open-source MATLAB tool, named ‘Plume Height Analyzer’ (PHA), which is able to analyze images and videos of explosive eruptions derived from visible cameras, with the objective of automatically identifying the temporal evolution of eruption columns. PHA is a self-customizing tool, i.e., before operational use, the user must perform an iterative calibration procedure based on the analysis of images of previous eruptions of the volcanic system of interest, under different eruptive, atmospheric and illumination conditions. The images used for the calibration step allow the computation of ad hoc expressions to set the model parameters used to recognize the volcanic plume in new images, which are controlled by their individual characteristics. Thereby, the number of frames used in the calibration procedure will control the goodness of the model to analyze new videos/images and the range of eruption, atmospheric, and illumination conditions for which the program will return reliable results. This also allows improvement of the performance of the program as new data become available for the calibration, for which PHA includes ad hoc routines. PHA has been tested on a wide set of videos from recent explosive activity at Mt. Etna, in Italy, and may represent a first approximation toward a real-time analysis of column height using visible cameras on erupting volcanoes.
In the last few decades, volcanic monitoring using remote sensing systems has become an essential tool to investigate the effects of volcanic activity on environment, climate, human health and aviation, as well as to give insights into volcanic processes. Compared to satellite measurements, ground-based instruments offer continuous spatial and temporal coverage capable of providing high resolution and high sensitivity data. This work presents a new simplified prototype of a Thermal InfraRed (TIR) system (named “VIRSO2”). The instrument comprises three cameras, one working in the visible and two in the TIR (8–14 μm). In front of one of the two TIR cameras, an 8.7 μm filter is placed. The system is designed for detection of volcanic emission, geometry estimation, columnar content of SO2 and ash, and SO2 flux retrievals. The retrieval procedures developed are detailed starting from the geometric characterization with wind direction correction, the calibration by considering the effects of filter multireflections and temperature, and the SO2 mass by exploiting MODTRAN radiative transfer model (RTM) simulations. The SO2 flux is then computed by applying the traverse method, with the plume speed obtained from the wind speed at the crater altitude. As test cases, the measurements collected at Etna volcano (Italy) on the 1 April 2021 during a lava fountain episode and the 30 August 2024 during a quiescent phase have been considered. The results show that the system can provide reliable information on plume detection, altitude, and SO2 flux. The simplicity, low cost, and the possibility of carrying out measurements at a safe distance from the vent both day and night, make this system ideal for real-time monitoring of volcanic emissions, thus helping to provide information on the state of activity of the volcano and therefore to mitigate the effect that these natural phenomena have on humans and the environment.
