Thermal remote sensing of sea surface temperature

Sea surface temperature has been an important application of remote sensing from space for three decades. This chapter first describes well-established methods that have delivered valuable routine observations of sea surface temperature for meteorology and oceanography. Increasingly demanding requirements, often related to climate science, have highlighted some limitations of these ap-proaches. Practitioners have had to revisit techniques of estimation, of characterising uncertainty, and of validating observations—and even to reconsider the meaning(s) of “sea surface temperature”. The current understanding of these issues is reviewed, drawing attention to ongoing questions. Lastly, the prospect for thermal remote sens-ing of sea surface temperature over coming years is discussed

SATELLITE AND IN SITU GROUND TEMPERATURE

Ground thermal anomalies in volcanic-hydrothermal systems, where the outflow of hot fluids gives rise to fumarolic fields, soil degassing, and hot soils, have, up to now, rarely been investigated by using satellite. Here we report a comparison between surface temperature derived by satellite data and a large data set of measured soil temperatures and CO2 fluxes for a volcanic-hydrothermal system, the Solfatara of Pozzuoli (Campi Flegrei, Italy). Surface temperatures derived from ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) data are compared with soil temperatures and CO2 fluxes from four surveys performed in 2003, 2010, and in 2014. The good match between the spatial distributions of computed and measured temperatures suggests the adequacy of satellite data to describe the Solfatara thermal anomaly, while the correspondence between temperatures and CO2 fluxes, evidences the link between degassing and heating processes. The ASTER derived surface temperatures (14–37°C) are coherent with those measured in the soil (10–97°C at 10 cm depth), considering the effect of the thermal gradients which characterize the degassing area of Solfatara. This study shows that satellite data can be a very powerful tool with which to study surface thermal anomalies, and can provide a supplementary tool to monitor thermal evolution of restless volcanoes

Wavelength influence in sub-pixel temperature retrieval using the dual-band technique

The thermal model proposed by Crisp and Baloga (1990) for active lava flows considers thermal flux as a func- tion of the fractional area of two thermally distinct radiant surfaces. In this model, the larger surface area corre- sponds to the cooler crust of the flow and the other, much smaller to fractures in the crust. These cracks temper- ature is much higher than the crust one and approaches the temperature of the molten or plastic interior flow. The dual-band method needs two distinct SWIR (short wave infrared) bands to formulate a two equations sys- tem from the simultaneous solution of the Planck equation in each band. The system solutions consist in the crust temperature and the fractional area of the hot component. The dual band technique originally builds on data ac- quired by sensors (such as Landsat TM) with two SWIR bands only. The use of hyperspectral imaging spectrom- eters allows us to test the dual-band technique using different wavelengths in the SWIR range of the spectrum. DAIS 7915 is equipped with 40 bands into the range 1.54-2.49 nm which represent potential input in dual band calculation. This study aims to compare results derived by inserting assorted couples of wavelengths into the equation system. The analysis of these data provides useful information on dual-band technique accuracy

Comparison of ASI-PRISMA Data, DLR-EnMAP Data, and Field Spectrometer Measurements on “Sale ‘e Porcus”, a Salty Pond (Sardinia, Italy)

A comparison between the ASI-PRISMA (Agenzia Spaziale Italiana-PRecursore IperSpettrale della Missione Applicativa) DLR-EnMAP (German Aerospace Center—Environmental Mapping and Analysis Program) data and field spectrometer measurements has been performed. The test site, located at the “Sale ‘e Porcus” pond (hereafter SPp) in Western Sardinia, Italy, offers particularly homogenous characteristics, making it an ideal location not only for experimentation but also for calibration purposes. Three remote-sensed data acquisitions have been performed by these agencies (ASI and DLR) starting on 14 July 2023 and continuing until 22 July 2023. The DLR-EnMAP data acquired on 22 July overestimates both that of the ASI-PRISMA and the 14 July DLR-EnMAP radiance in the VNIR region, while all the datasets are close to each other, up to 2500 nm, for all considered days. The average absolute mean difference between the reflectance values estimated by the ASI-PRISMA and DLR-EnMAP, in the test area, is around 0.015, despite the small difference in their time of acquisition (8 days); their maximum relative difference value occurs at about 2100 nm. In this study, we investigate the relationship between the averaged ground truth value of reflectance, acquired by means of a portable ASD FieldSpec spectoradiometer, characterizing the test site and the EO reflectance data derived from the official datasets. FieldSpec measurements confirm the quality of both the ASI-PRISMA and DLR-EnMAP’s reflectance estimations

A UAS System for Observing Volacanoes and Natural Hazards

Fixed or rotary wing manned aircraft are currently the most commonly used platforms for airborne reconnaissance in response to natural hazards, such as volcanic eruptions, oil spills, wild fires, earthquakes. Such flights are very often undertaken in hazardous flying conditions (e.g., turbulence, downdrafts, reduced visibility, close proximity to dangerous terrain) and can be expensive. To mitigate these two fundamental issues--safety and cost--we are exploring the use of small (<100kg), relatively inexpensive, but effective, unmanned aerial vehicles (UAVs) for this purpose. As an operational test, in 2004 we flew a small autonomous UAV in the airspace above and around Stromboli Volcano. Based in part on this experience, we are adapting the RAVEN- INGV system for such natural hazard surveillance missions. RAVEN- INGV has a 50km range, with a 3.5m wingspan, main fuselage length of 4.60m, and maximum weight of 56kg. It has autonomous flight capability and a ground control station for mission planning and control. It will carry a variety of imaging devices, including a visible camera, and an IR camera. Such flexible, capable, and easy-to-deploy UAV systems may significantly shorten the time necessary to characterize the nature and scale of the natural hazard threats if used from the outset of, and systematically during, natural hazard events. When appropriately utilized, such UAVs can provide a powerful new hazard mitigation and documentation tool for civil protection hazard responders. This research was carried out under the auspices of the Italian government, and, in part, under contract to NASA at the Jet Propulsion Laboratory

Spectral emissivity and temperature maps of the Solfatara crater from DAIS hyperspectral images

Quantitative maps of surface temperature and spectral emissivity have been retrieved on the Solfatara crater at Pozzuoli (Naples) from remote sensing hyperspectral data. The present study relies on thermal infrared images collected on July 27, 1997 by the DAIS hyperspectral sensor owned by the German aerospace center (DLR). The Emissivity Spectrum Normalization method was used to make temperature and emissivity estimates. Raw data were previously transformed in radiance and corrected for the atmospheric contributions using the MODTRAN radiative transfer code and the sensor response functions. During the DAIS flight a radiosonde was launched to collect the atmospheric profiles of pressure, temperature and humidity used as input to the code. Retrieved tem- perature values are in good agreement with temperature measurements performed in situ during the campaign. The spectral emissivity map was used to classify the image in different geo-mineralogical units with the Spec- tral Angle Mapper method. Areas of geologic interest were previously selected using a mask obtained from an NDVI image calculated with two channels of the visible (red) and the near infrared respectively

The Interferometric Use of Radar Sensors for the Urban Monitoring of Structural Vibrations and Surface Displacements

In this paper, we propose a combined use of real aperture radar (RAR) and synthetic aperture radar (SAR) sensors, within an interferometric processing chain, to provide a new methodology for monitoring urban environment and historical buildings at different temporal and spatial scales. In particular, ground-based RAR measurements are performed to estimate the vibration displacements and the natural oscillation frequencies of structures, with the aim of supporting the understanding of the building dynamic response. These measurements are then juxtaposed with ground-based and space-borne SAR data to monitor surface deformation phenomena, and hence, point out potential risks within an urban environment. In this framework, differential interferometric SAR algorithms are implemented to generate short-term (monthly) surface displacement and long-term (annual) mean surface displacement velocity maps at local (hundreds m2) and regional (tens km2) scale, respectively. The proposed methodology, developed among the activities carried out within the national project Programma Operativo Nazionale MASSIMO (Monitoraggio in Area Sismica di SIstemi MOnumentali), is tested and discussed for the ancient structure of Saint Augustine compound, located in the historical center of Cosenza (Italy) and representing a typical example of the Italian Cultural Heritage

Ten years of volcanic activity at Mt Etna: High-resolution mapping and accurate quantification of the morphological changes by Pleiades and Lidar data

Abstract The topography of Mt. Etna, Italy, is subjected to continuous modifications depending on intensity and magnitude of eruptions that frequently occur at the volcano summit and flanks. In order to make high-resolution maps of morphological changes and accurately calculate the overall volume of the erupted products (e.g., lava flows, tephra fall out, scoriae cones) in ten years, we have compared the altimetry models of Mt. Etna derived from 2005 Airborne Laser Scanning data and 2015 Pleiades stereo satellite imagery. Both models cover a common area of 400 km2 with spatial resolution of 2 m and comparable vertical accuracy (RMS

Airborne LiDAR and Hyperspectral Data to Support the Seismic Vulnerability of Urban Environments

The seismic vulnerability analysis of urban environments is an operational issue that concerns the comprehensive knowledge of both building structural features and soils geophysical parameters, especially when considering areas that are prone to hydrogeological and seismic disasters. The protection of such environments, together with the population growth and the urbanization processes, requires a multi-disciplinary approach aiming at providing both an effective assessment of urban resources and synthetic parameters for managing post crisis events, restoration activities and search & rescue operations. Within such a framework, airborne Light Detection and Ranging (LiDAR) and Hyperspectral sensors have demonstrated to be powerful remote sensing instruments, whose jointly use allow providing meaningful parameters to describe both the topographic settings of urbanized areas and the buildings properties, in terms of geometrical, spectral and structural features. Based on this rationale, in this study, the operational benefits obtained by combining airborne LiDAR and Hyperspectral measurements are provided to support the seismic vulnerability assessment of urban seismic areas. The digital elevation model as well as the building height and the shape of the observed area are gathered by using airborne LiDAR measurements. Spectral and structural information of urban buildings are provided through the supervised classification of IMSpectorV10E VNIR (wavelength range between 400 and 1000nm subdivided into 503 bands) measurements acquired by the IPERGEO sensor. The objective is to combine the different products provided by LiDAR and Hyperspectral image processing analysis within a Geographic Information System (GIS) platform, to evaluate the intrinsic properties of buildings (e.g. perimeter, covered area, height and type of roofs) together with the topographic features of the surrounding area (e.g. the surface height and slope) for providing synthetic parameters and thematic maps useful for seismic assessment and mitigation purposes, such as: (i) the identification of steep slope areas, (ii) the analysis of building roof typology for supporting the evaluation of structural load conditions, (iii) the detection of critical structures (e.g. asbestos buildings), (iv) the identification of primary roads (in terms of escape or access routes) for supporting search and rescue operations, (v) the analysis of main road conditions after building collapses. Meaningful experimental results, gathered for the historical center of Cosenza city (Italy), allow demonstrating the benefits of the proposed approach for both seismic assessment and mitigation purposes. The present work is supported and funded by Ministero dell'Universita, dell'Istruzione e della Ricerca (MIUR) under the project PON01-02710 "MASSIMO" - "Monitoraggio in Area Sismica di SIstemi MOnumentali"

A S.M.A.R.T. system for the seismic vulnerability mitigation of Cultural Heritages

Both assessment and mitigation of seismic vulnerability connected to cultural heritages monitoring are non-trivial issues, based on the knowledge of structural and environmental factors potential impacting the cultural heritage. A holistic approach could be suitable to provide an effective monitoring of cultural heritages within their surroundings at different spatial and temporal scales. On the one hand, the analysis about geometrical and structural properties of monuments is important to assess their state of conservation, their response to external stresses as well as anomalies related to natural and/or anthropogenic phenomena (e.g. the aging of materials, seismic stresses, vibrational modes). On the other hand, the investigation of the surrounding area is relevant to assess environmental properties and natural phenomena (e.g. landslides, earthquakes, subsidence, seismic response) as well as their related impacts on the monuments. Within such a framework, a multi-disciplinary system has been developed and here presented for the monitoring of cultural heritages for seismic vulnerability assessment and mitigation purposes*. It merges geophysical investigations and modeling, in situ measurements and multi-platforms remote sensing sensors for the non-destructive and non-invasive multi-scales monitoring of historic buildings in a seismic-prone area. In detail, the system provides: a) the long-term and the regional-scale analysis of buildings’ environment through the integration of seismogenic analysis, airborne magnetic surveys, space-borne Synthetic Aperture Radar (SAR) and multi-spectral sensors. They allow describing the sub-surface fault systems, the surface deformation processes and the land use mapping of the regional-scale area on an annual temporal span; b) the short-term and the basin-scale analysis of building’s neighborhood through geological setting and geotechnical surveys, airborne Light Detection And Radar (LiDAR) and ground-based SAR sensors. They enable assessing the site seismic effects, the built-up structural features and the surface deformation processes of the local-scale area on a monthly temporal span; c) the real- to near-real-time and building scale analysis of the heritage through proximal remotely sensing tools (e.g. terrestrial laser scanning, infrared thermal cameras and real aperture radar), combined with ambient vibration tests. They allow analyzing geometric, structural and material properties / anomalies of buildings as well as the state of conservation of structures on a real-time temporal span. The proposed approach is: Specific (it targets the cultural heritages monitoring for seismic mitigation purposes); Measurable (it provides synthetic descriptors or maps able to quantify structural and the environmental properties / anomalies / trends); Action-oriented (it provides information to plan consolidation and restoration actions for prevention activity); Relevant (it allows achieving consolidated results for cultural heritage monitoring); Time-related (it specifies when the results can be achieved). Meaningful results, obtained for the Saint Augustine Complex (XVI century) located in the historic center of the Calabrian chief town of Cosenza, are presented in terms of a web-based Geographic Information System (GIS) platform and a 3-dimensional (3D) visual software for the monitoring of environmental/urban landscapes and buildings. These tools represent the added-value products of the proposed SMART system, which allow integrating and combining multi-sensors analyses in order to support end-users involved into a cultural heritage monitoring.Copernicus MeetingsPublishedVienna | Austria | 17–22 April 20165T. Sismologia, geofisica e geologia per l'ingegneria sismic