513 research outputs found
Volcanic Water Vapour Abundance Retrieved Using Hypespectral Data
In the present study a remote sensing differential
absorption technique, already developed to calculate the atmospheric water vapour abundance, has been adapted to calculate water
vapour columnar abundance in tropospheric volcanic plume. Water
vapour is the most abundant gas of a volcanic plume released into the atmosphere from an active volcanic system. The technique is based on the correlation between the dip in the spectral curve measured by the spectrometer were water vapour absorptions bands are presents, and the precipitable water content in the column.
Airborne and satellite remote sensing images in the infrared
wavelength range were used. The technique has been applied to data acquired over two different degassing volcanoes. The Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) acquired data over the Hawaiian Pu’u’O’o Vent cone of the Kilauea volcano on April 2000. The Hyperion sensor on EO-1 satellite has been requested to acquire data on July 2003, during a ground-based measurements campaign on Mt. Etna (Italy). The result is the spatial distribution of water vapour abundance of the Mt. Etna and of the Pu`u` O`o Vent volcanic plumes. A comparison between the two results has been done, showing the differences in the volcanic activity. The algorithm produces reliable results compared to the ground based measurements in the plume area acquired during a measurements campaign over Mt. Etna
Temperature distribution analysis of July 2001 Mt. Etna eruption observed by the airborne hyperspectral sensor MIVIS
On 17th and 18th July 2001, several fractures opened on Mt. Etna southern flank generating different lava flows
spreading both in Valle del Bove and towards Nicolosi. On 29th July the image spectrometer MIVIS was flown
over Mt. Etna to acquire high-resolution images of the eruption. The MIVIS airborne campaign was planned simultaneously
with TERRA, EO-1 and Landsat 7 satellite acquisitions, in order to compare hyperspectral and
multispectral data referred to active lavas. This work focuses on the thermal mapping of lava flows, taking advantage
of MIVIS sensor high technical performances. The MIVIS high spatial resolution allows a detailed
analysis of the lava flow topographic distribution. Its 12 bit dynamic range consents an estimate of the temperature
even for the «hottest» pixels. The main target of this work is the evaluation of the energy flux by means of
remote-sensing techniques. Surface temperature analysis was performed on distinct lava flows using the dualband
technique. These quantities were compared with the integrated temperatures retrieved using the MIVIS
thermal infrared bands. The influence of topography was also considered in the flux calculation using a Digital
Elevation Model (DEM) of Mt. Etna
Characterization of volcanic thermal anomalies by means of sub-pixel temperature distribution analysis
Abstract: The simultaneous solution of the Planck equation (involving the widely used “dual-band”
technique) using two shortwave infrared (SWIR) bands allows for an estimate of the fractional area of the
hottest part of an active lava flow (fh), and the background temperature of the cooler crust (Tc). The use of a
high spectral and spatial resolution imaging spectrometer with a wide dynamic range of 15 bits (DAIS 7915)
in the wavelength range from 0.501 to 12.67 µm resulted in the identification of crustal temperature and
fractional areas for an intra-crater hot spot at Mount Etna, Italy. This study indicates the existence of a
relationship between these Tc and fh extracted from DAIS and Landsat TM data. When the dual band
equation system is performed on a lava flow, a logarithmic distribution is obtained from a plot of the
fractional area of the hottest temperature versus the temperature of the cooler crust. An entirely different
distribution is obtained over active degassing vents, where increases in Tc occur without any increase in fh.
This result indicates that we can use scatter plots of Tc vs. fh to discriminate between different types of
volcanic activity, in this case between degassing vents and lava flows, using satellite thermal data
First principle theory of correlated transport through nano-junctions
We report the inclusion of electron-electron correlation in the calculation
of transport properties within an ab initio scheme. A key step is the
reformulation of Landauer's approach in terms of an effective transmittance for
the interacting electron system. We apply this framework to analyze the effect
of short range interactions on Pt atomic wires and discuss the coherent and
incoherent correction to the mean-field approach.Comment: 5 pages, 3 figure
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 temperature 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 Spectral 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
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 function
of the fractional area of two thermally distinct radiant surfaces. In this model, the larger surface area corresponds
to the cooler crust of the flow and the other, much smaller to fractures in the crust. These cracks temperature
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 system
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 acquired
by sensors (such as Landsat TM) with two SWIR bands only. The use of hyperspectral imaging spectrometers
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
MAC Europe 1991 campaign: AIRSAR/AVIRIS data integration for agricultural test site classification
During summer 1991, multi-sensor data were acquired over the Italian test site 'Otrepo Pavese', an agricultural flat area in Northern Italy. This area has been the Telespazio pilot test site for experimental activities related to agriculture applications. The aim of the investigation described in the following paper is to assess the amount of information contained in the AIRSAR (Airborne Synthetic Aperture Radar) and AVIRIS (Airborne Visible/Infrared Imaging Spectrometer) data, and to evaluate classification results obtained from each sensor data separately and from the combined dataset. All classifications are examined by means of the resulting confusion matrices and Khat coefficients. Improvements of the classification results obtained by using the integrated dataset are finally evaluated
Combined Use of Terrestrial Laser Scanning and IR Thermography Applied to a Historical Building
Abstract: The conservation of architectural heritage usually requires a multidisciplinary
approach involving a variety of specialist expertise and techniques. Nevertheless, destructive
techniques should be avoided, wherever possible, in order to preserve the integrity of the
historical buildings, therefore the development of non-destructive and non-contact
techniques is extremely important. In this framework, a methodology for combining the
terrestrial laser scanning and the infrared thermal images is proposed, in order to obtain a
reconnaissance of the conservation state of a historical building. The proposed case study is
represented by St. Augustine Monumental Compound, located in the historical centre of the
town of Cosenza (Calabria, South Italy). Adopting the proposed methodology, the paper
illustrates the main results obtained for the building test overlaying and comparing the
collected data with both techniques, in order to outline the capabilities both to detect the
anomalies and to improve the knowledge on health state of the masonry building. The 3D
model, also, allows to provide a reference model, laying the groundwork for implementation
of a monitoring multisensor system based on the use of non-destructive techniques
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 contributes 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
temperature values are in good agreement with temperature measures performed in situ during the
campaign. The spectral emissivity map was used to classify the image in different geomineralogical
units with the Spectral 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
Aerosol optical thickness of Mt. Etna volcanic plume retrieved by means of the Airborne Multispectral Imaging Spectrometer (MIVIS)
Within the framework of the European MVRRS project (Mitigation of Volcanic Risk by Remote Sensing
Techniques), in June 1997 an airborne campaign was organised on Mt. Etna to study different characteristics of
the volcanic plume emitted by the summit craters in quiescent conditions. Digital images were collected with
the Airborne Multispectral Imaging Spectrometer (MIVIS), together with ground-based measurements. MIVIS
images were used to calculate the aerosol optical thickness of the volcanic plume. For this purpose, an inversion
algorithm was developed based on radiative transfer equations and applied to the upwelling radiance data measured
by the sensor. This article presents the preliminary results from this inversion method. One image was selected
following the criteria of concomitant atmospheric ground-based measurements necessary to model the atmosphere,
plume centrality in the scene to analyse the largest plume area and cloudless conditions. The selected image was
calibrated in radiance and geometrically corrected. The 6S (Second Simulation of the Satellite Signal in the Solar
Spectrum) radiative transfer model was used to invert the radiative transfer equation and derive the aerosol optical
thickness. The inversion procedure takes into account both the spectral albedo of the surface under the plume and
the topographic effects on the refl ected radiance, due to the surface orientation and elevation. The result of the
inversion procedure is the spatial distribution of the plume optical depth. An average value of 0.1 in the wavelength
range 454-474 nm was found for the selected measurement day
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