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This paper focuses on the detection, from a stack of repeated-pass interferometric synthetic aperture radar (SAR) images, of such changes causing a target to completely lose the correlation between one epoch and another. This can be the consequence of human activities, such as construction, destruction, and agricultural activities, and also be the consequence of hazards, such as earthquake, landslides, or flooding, to buildings or terrains. The millimetric sensitivity of SAR makes it valuable for detecting such changes. This paper approaches two coherent change detection methods: a space coherent, time incoherent one and a full space and time coherent one, both based on the generalized likelihood ratiob (LR) test. A preliminary validation of the method is provided by processing two Sentinel-1 data stacks of 2016 Central Italy earthquake and by comparing the results with the map of damaged buildings in Amatrice and Accumoli made by Copernicus Emergency Management Service. [ABSTRACT FROM AUTHOR]

This paper describes the results obtained by the application of an innovative environmental monitoring technique able to estimate rainfall intensity in real time by processing the attenuation of microwave satellite link signal measured by low cost sensors. The satellite that has been used during our work, Turksat 42° E, belongs to the plethora of satellites operating for television and radio channel broadcasting. Each sensor exploits off the shelf components, is equipped with a radio frequency power-measuring unit, and provides connectivity to the server over a wide area network. A validation of the approach with a field comparison experiment at the urban scale, comprising three measurement sites equipped with such sensors, was established since autumn 2016 in the municipality of Genoa, Italy. Point-scale rainfall intensity measurements made by two calibrated tipping-bucket rain gauges constitute the reference for the comparative analysis of the microwave sensors performance. The dynamic calibration of the rain gauges was carried out by using an automatic calibration rig and the measurements have been processed with advanced algorithms to reduce counting errors. The experimental setup allowed a full characterization of the microwave signal trends as a function of different precipitation. The results showed a strong correlation between the microwave signal attenuation and the reference rainfall observations and demonstrated the possibility to retrieve ten-minute rain accumulations from the microwave links by adopting a proper electromagnetic model. The comparison between the different measuring systems is performed by computing the time series statistics and the frequency of the rain conditions for each precipitation event. [ABSTRACT FROM AUTHOR]

The article discusses the highlights of the 10th Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment (MicroRad'08) held in Florence, Italy from March 11 to 14, 2008. The opening speech by organizer Paolo Pampaloni was dedicated in memory of Professor Giovanni d'Auria of the University of Rome in Italy. A session on the Advanced Microwave Scanning Radiometer (AMSR) for Earth Observing System (EOS) was conducted. The meeting ended with a wine and cheese reception.

The European Space Agency Soil Moisture and Ocean Salinity (SMOS) mission was launched on November 2, 2009. Providing accurate soil moisture (SM) estimation is one of its main scientific objectives. Since the end of the commissioning phase, preliminary global SMOS SM data [Level 2 (L2) product] are distributed to users. In this paper, we carried out a first assessment of the reliability of this product through a comparison with in situ observed and modeled SM over three different sites: One is located in Luxemburg, and two are located in Italy. The period from August 1, 2010, to July 1, 2011, has been analyzed, giving us the opportunity to evaluate the satellite response to different SM states. The selected period is important for hydrological predictions as it is typically characterized by a sequence of transitions from dry to wet and from wet to dry conditions. In order to compare SMOS and ground SM measurements, a two-step approach has been applied. First, an exponential filter has been applied to approximate root-zone SM, and second, a cumulative distribution function matching has been employed to remove systematic differences between satellite and in situ observations and model simulations of SM. Our results indicate rather good reliability of the filtered and bias-corrected SM estimates derived from the first SMOS L2 products. Bearing in mind that an updated/advanced version of the SMOS SM product has been recently produced, our preliminary results already seem to confirm the potential of SMOS for monitoring of water in soils. [ABSTRACT FROM AUTHOR]

In this paper, a sensitivity analysis and procedure development for volcanic-plume sulfur dioxide and ash retrievals using ground thermal infrared camera have been carried out. The semiconductor device camera, considered as a reference, has a spectral range of 8-14 μm with noise equivalent temperature difference that is better than 100 mK at 300 K. The camera will be used to monitor and assess the hazards of Mt. Etna volcano to mitigate the risk and impact of volcanic eruptions on the civil society and transports. A minimum number of filters have been selected for sulfur dioxide (SO2) and volcanic ash retrievals. The sensitivity study has been carried out to determine the SO2 and volcanic ash minimum concentration detectable by the system varying the camera geometry and the atmospheric profiles. Results show a meaningful sensitivity increase considering high instrument altitudes and low camera-elevation angles. For all geometry configurations and monthly profiles, the sensitivity limit varies between 0.5 and 2 g · m-2 for SO2 columnar abundance and between 0.02 and 1 for ash optical depth. Two procedures to detect SO2 and ash, based on the least square fit method and on the brightness temperature difference (BTD) algorithm, respectively, have also been proposed. Results show that high concentration of atmospheric water vapor columnar content significantly reduces the ash-plume effect on the BTD. A water vapor-correction procedure introduced improves the ash retrievals and the cloud discrimination in every season, considering all the camera geometries. [ABSTRACT FROM AUTHOR]

This paper shows a model study about the emissivity of forests. Model outputs are compared with multifrequency airborne measurements carried out over five broadleaf forests in Italy. Two flights took place, in summer 1999 and winter 2002. Available ground truth included important variables, such as biomass, tree density, and average trunk diameter. This data set, in conjunction with allometric equations and information taken from the literature, is used to give inputs to the model. A general agreement between simulated and measured data is observed L-, C-, and X-bands. The same model is used to investigate the sensitivity of forest emissivity to soil moisture, woody volume, and average diameter. As expected, a moderate effect of soil moisture is observed only at L-band and for forests with a lower woody volume. At L-band, the model predicts a general increase emissivity with woody volume but indicates that also the trunk diameter exerts an important influence, since it is a variable which controls several geometrical properties. These results allow us to single out the influence of soil moisture, woody volume, and geometrical properties at L-band. The increase of emissivity with frequency, observed in experimental data, is interpreted by means of electromagnetic considerations about branch scattering. [ABSTRACT FROM AUTHOR]

In this paper, we report the results of an experimental study aimed toward investigating microwave emission from forests. The experiment was carried out in 2006 on two forest stands of poplar (Populus alba) and pine (Pinus italica), using ground-based microwave radiometers at the L-, C-, X-, Ku-, and Ka-bands, in H and V polarizations. Measurements on poplar were performed on different dates and at different incidence and azimuth angles, looking downward (from the top of trees and from below the crown) and upward (from the soil level). Only one downward-looking measurement was carried out over a pine plot with dry soil in April. All the remote sensing measurements were complemented with "ground-truth" data. The collected experimental data made it possible to quantify the spectral signatures of poplar, as well as the variation of angular trends of brightness temperature in different seasons of the year. The sensitivity of L-band emission to soil properties and leaf biomass was also investigated. Moreover, the measurements on poplar, combined with a simple radiative transfer model (the so-called omega-tau equation), allowed estimating the transmissivity of the canopy with and without leaves. The analysis of data has shown that for the observed forest type, the sensitivity to soil moisture under defoliated trees can be noted at both the L- and C-bands. [ABSTRACT FROM AUTHOR]

In this paper, we propose an analysis on the joint effect of hyperspectral and light detection and ranging (LIDAR) data for the classification of complex forest areas. In greater detail, we present: 1) an advanced system for the joint use of hyperspectral and LIDAR data in complex classification problems; 2) an investigation on the effectiveness of the very promising support vector machines (SVMs) and Gaussian maximum likelihood with leave-one-out-covariance algorithm classifiers for the analysis of complex forest scenarios characterized from a high number of species in a multisource framework; and 3) an analysis on the effectiveness of different LIDAR returns and channels (elevation and intensity) for increasing the classification accuracy obtained with hyperspectral images, particularly in relation to the discrimination of very similar classes. Several experiments carried out on a complex forest area in Italy provide interesting conclusions on the effectiveness and potentialities of the joint use of hyperspectral and LIDAR data and on the accuracy of the different classification techniques analyzed in the proposed system. In particular, the elevation channel of the first LIDAR return was very effective for the separation of species with similar spectral signatures but different mean heights, and the SVM classifier proved to be very robust and accurate in the exploitation of the considered multisource data. [ABSTRACT FROM AUTHOR]

The factorization method (FM) has been applied to measurement data from a multistatic ground-penetrating radar operating in close proximity to the ground, which was used in a measurement campaign on the Joint Research Centre mine test lane in Ispra, Italy. This paper is targeted toward a future hand-held demining system. The according space limits restrict an independent positioning of transmit and receive antennas. Hence, very small multistatic datasets are obtained, representing a difficult case for the reconstruction with the FM. [ABSTRACT FROM AUTHOR]

Continuity of the European Remote Sensing Satellite Synthetic Aperture Radar (ERS SAR) archive by means of Envisat Advanced SAR (ASAR) data acquired from March 2002 has introduced the problem of the coherent combination of images coming from sensors with slightly different frequencies. The spectral shift principle states that in case of extended distributed targets, the frequency shift is equivalent to a change of looking angle. In this paper, the same principle is exploited to analyze the behavior of permanent scatterers (PSs) with an extension that is smaller than the ground resolution cell. The conditions under which the PSs identified by ERS can be continued by Envisat are then theoretically determined and experimentally validated. Moreover, this analysis shows that acquisitions characterized by different frequencies can be used to identify the slant-range position of scatterers with high subcell accuracy (tens of centimeters). From the processing side, a very precise images coregistration step is required to get the results described in this paper. [ABSTRACT FROM AUTHOR]

The alpine village of Lamosano, Belluno, Italy, located near a wide and active landslide, has been seriously threatened by ground instabilities since 1960. In this paper, the results obtained by two different remote-monitoring techniques, synthetic aperature radar interferometry and three-dimensional laser-scanner imaging, planned for Lamosano hazard assessment, are presented. Both techniques compare images taken at different times to map and classify changes that occurred on the imaged scenario. The radar and laser data are gathered at the same dates with about ten-month temporal separation. The displacements measured separately by each of the two techniques highlight a similar sliding motion on the Lamosano village area, providing a good validation to each other and contributing to the definition of the village instability hazard. [ABSTRACT FROM AUTHOR]

The small hyperspectral imager Compact High- Resolution Imaging Spectrometer (CHRIS) is the most important instrument for Earth observation included in the payload of the European Space Agency Third-Part Mission Project for On-Board Autonomy (PROBA)-1 satellite. This instrument has provided dozens of images in several target areas in the world, and a good number of acquisitions are available for the test site of Frascati and Tor Vergata, Italy. This paper reports several results concerning the generation of thematic maps obtained from CHRIS mode-3 imagery. The potential of the use of different configurations for the input vector exploiting multispectral, multiangular, and multitemporal measurements has been investigated, and the results have been evaluated and compared in terms of accuracy in the classification. The core of the decision task has been developed using the neural network methodology. Indeed, this approach is characterized by a particular ease in performing nonlinear mapping of a multidimensional set of inputs into the output one. [ABSTRACT FROM AUTHOR]

Differential synthetic aperture radar interferometry (DInSAR) is a remote sensing technique that allows monitoring ground deformation with accuracy of the order of fractions of the radiated wavelength, by means of proper combination and processing of repeat-pass data. In contrast to the satellite case, application of such a technique to airborne data is not, today, a well-established task. Several airborne campaigns, involving mainly C/L-band data, have been planned in the last years to exploit the potentialities of these more flexible platforms for deformation monitoring. In this paper, we show the results of an airborne DInSAR X-band experiment carried out over the Perugia area (center of Italy) by using the OrbiSAR system. We discuss the processing chain applied to the acquired data, which allows achieving a satisfactory compromise between accuracy and efficiency. Eleven repeated passes were carried out in two days; two corner reflectors were located on the ground in a hilly region. One corner reflector was vertically moved between the two days to evaluate the system detection capability. Moreover, we carry out an analysis of all possible differential interferograms for a region 2 x 4 km wide. [ABSTRACT FROM AUTHOR]

This paper presents a differential synthetic aperture radar (SAR) interferometry (DIFSAR) approach for investigating deformation phenomena on full-resolution DIFSAR interferograms. In particular, our algorithm extends the capability of the small-baseline subset (SBAS) technique that relies on small-baseline DIFSAR interferograms only and is mainly focused on investigating large-scale deformations with spatial resolutions of about 100 x 100 m. The proposed technique is implemented by using two different sets of data generated at low (multilook data) and full (single-look data) spatial resolution, respectively. The former is used to identify and estimate, via the conventional SBAS technique, large spatial scale deformation patterns, topographic errors in the available digital elevation model, and possible atmospheric phase artifacts; the latter allows us to detect, on the full-resolution residual phase components, structures highly coherent over time (buildings, rocks, lava, structures, etc.), as well as their height and displacements. In particular, the estimation of the temporal evolution of these local deformations is easily implemented by applying the singular value decomposition technique. The proposed algorithm has been tested with data acquired by the European Remote Sensing satellites relative to the Campania area (Italy) and validated by using geodetic measurements. [ABSTRACT FROM AUTHOR]

The southern area of Italy is characterized by the presence of many active volcanic areas. In Pozzuoli (Naples, Italy), an urban area characterized by high volcanic risk, a gas emitting site is present. An high percentage of CO2 is emitted, whose atmospheric concentration measurement is an important task in many environmental and scientific applications. In this paper, we describe the utilization over that area of a mobile infrared (IR) laser system, able to measure the CO2 concentration along rectilinear atmospheric paths up to 1-km length, and the result of tomographic processing applied to retrieve a two-dimensional CO2 concentration field. The laser system computes the link averaged concentration by processing the received IR laser radiation propagated along an open-air rectilinear link connecting the transmitter/receiver laser unit and a passive retroreflector device. A one-day measurement campaign has been made and 15 different atmospheric propagation links were considered moving the transmitter/receiver unit and some retroreflectors. [ABSTRACT FROM AUTHOR]

This study aims at relating the stickiness parameter ($\tau$) of the dense media radiative transfer theory in quasi-crystalline approximation of Mie scattering of densely packed sticky spheres (DMRT-QMS), to the physical parameters of the layered snowpack. A relationship has been derived to express $\tau $ , which modulates the attractive contact force between ice spheres, as a function of ice volume fraction ($\phi $) and coordination number ($n_{c}$). Since $\tau $ is not a measurable parameter, this is a step forward with respect to what is commonly made in the literature, where $\tau $ is assumed as an arbitrary parameter, generally ranging between 0.1 and 0.3, to fit simulated backscattering data with those measured. As a first validation, DMRT-QMS was integrated with the SNOWPACK model to simulate backscattering at X-band (9.6 GHz) driven by nivo-meteorological data acquired on a test area located in Monti Alti di Ornella, Italy. The simulations were compared with Synthetic Aperture Radar COSMO-SkyMed (CSK) satellite observations. The results show a significant agreement ($R^{2} =0.68$), although for a limited dataset of eight points in a unique winter season. [ABSTRACT FROM AUTHOR]

River discharge is an important variable to measure in order to predict droughts and flood occurrences. Once the cross-sectional geometry of the river is known, discharge can be inferred from water level and surface flow velocity measurements. Since river discharges are of particular interest during extreme weather events, when river sites cannot be safely accessed, noncontact sensing technologies are particularly appealing. To this purpose, this work proposes a prototype of a low-cost continuous wave (CW) Doppler radar sensor, which is able to monitor the surface flow velocity of rivers. The prototype is tested at two gauged sites in central Italy, along the Tiber River. The surface flow velocity distribution across the river is monitored by means of the analysis of received Doppler signal. The surface velocity statistics are then extracted using a novel algorithm that is optimized to run on a microprocessor platform with minimal computing power (ArduinoUNO). In particular, the radar measurements are used to initialize a 2-D entropy-based velocity model (EVM) that is able to estimate river discharges in any flow condition. Finally, the results concerning the observed discharge provided by the EVM prove to be comparable with those obtained with more expensive commercial solutions. The results are important since the described methodology can be extended to small-size Doppler radar sensors onboard unmanned aerial vehicles (UAVs), the latter providing a method for mapping surface velocity of rivers. [ABSTRACT FROM AUTHOR]

Morphological attribute profiles (APs) are defined as a generalization of the recently proposed morphological profiles (MPs). APs provide a multilevel characterization of an image created by the sequential application of morphological attribute filters that can be used to model different kinds of the structural information. According to the type of the attributes considered in the morphological attribute transformation, different parametric features can be modeled. The generation of APs, thanks to an efficient implementation, strongly reduces the computational load required for the computation of conventional MPs. Moreover, the characterization of the image with different attributes leads to a more complete description of the scene and to a more accurate modeling of the spatial information than with the use of conventional morphological filters based on a predefined structuring element. Here, the features extracted by the proposed operators were used for the classification of two very high resolution panchromatic images acquired by Quickbird on the city of Trento, Italy. The experimental analysis proved the usefulness of APs in modeling the spatial information present in the images. The classification maps obtained by considering different APs result in a better description of the scene (both in terms of thematic and geometric accuracy) than those obtained with an MP. [ABSTRACT FROM AUTHOR]

Multispectral data acquired by Spinning Enhanced Visible and InfraRed Imager (SEVIRI) onboard the geostationary platform Meteosat Second Generation (MSG2), located at 0° longitude, were analyzed to assess the payload suitability for quantitative volcano monitoring. In times of good infrared transparency of the troposphere, SEVIRI data proved particularly suited to detect the onset of effusive eruptions and to monitor the related lava flows with 15-min refresh rates. After development of a code allowing for fast automated processing of the 96 data streams downlinked daily by MSG2, thorough monitoring tests were carried out on the 2007 eruptions of Stromboli (Aeolian Islands, Italy) and Piton de la Fournaise (Reunion Island, France). The results in radiant flux and effusion rate provided by use of thermal, mid-, and short infrared bands of SEVIRI were validated by exploiting simultaneous MODIS overpasses by Terra and Aqua, up to four times daily. [ABSTRACT FROM AUTHOR]

A spatial characterization of the midlatitude meso-scale rain fields from C-band radar measurements is performed by means of a systematic analysis and modeling of convective rain-cell bidimensional shapes and spatial correlation. A large rainfall dataset that is derived from an operational C-band dual-polarized radar, which is placed in S. Pietro Capofiume near Bologna (Italy), has been collected and analyzed for this purpose. Different models of convective rainy horizontal structures are described and compared. Special attention is devoted to the consolidated unimodal models (or unimodal patterns) like GAUCELL with a Gaussian rain-rate profile and EXCELL with an exponential rain-rate profile, and the hybrid models like HYCELL and DEXCELL based on a proper combination of the previous unimodal models. The new hybrid model DEXELL, which is introduced here, is an extension of the HYCELL model, which is previously proposed in literature. A pixel-by-pixel model numerical integration is carried out in order to perform a homogeneous comparison between the rain-cell model and the measured features such as peak, average, root mean square, gradient average, and gradient deviation of rain rate. A maximum-likelihood algorithm, which is expressed in terms of the principal component of the previous rain-cell features, is introduced to estimate rain-cell pattern parameters from the available radar data. A detailed sensitivity analysis, which is devoted to find the best behavior in terms of root-mean-square error and correlation coefficient between the modeled and measured rain-cell features, is finally carried out. [ABSTRACT FROM AUTHOR]

Several popular bistatic calibration techniques are investigated and comparisons made between the relative merits of the various techniques. The analysis addresses sensitivity to object alignment error, sensitivity to polarization impurity, and ease of implementation. Both theoretical concepts and practical considerations are discussed based on measurements accomplished at the European Microwave Signature Laboratory of the European Come mission Joint Research Center, Ispra, Italy. This facility has the capability to produce far-field fully polarimetric precision bistatic measurements in a 30-cm-diameter quiet zone, suitable for comparing different calibration methods. [ABSTRACT FROM AUTHOR]

The application of ground-based radar iterferometry for landslide monitoring is here analyzed: a case study based on an experimental campaign carried out in Italy in the year 2002 is discussed. Interferometric data obtained from coherent synthetic aperture radar (SAR) images acquired by means of C-band ground-based equipment are analyzed. The campaign was aimed at retrieving potential terrain movements of a small landslide observed hundreds of meters away. Critical aspects related to spatial and temporal decorrelation are discussed: the use of optical photogrammetry as a technique for evaluating mechanical stability and correcting geometric distortion is presented. Results also confirmed that the application of ground-based radar interferometry can be attractive and effective if the acquired SAR images maintain an adequate coherence on different dates. [ABSTRACT FROM AUTHOR]

Five empirical and nonempirical parametric topographic normalization methods (the cosine, SCS, Minnaert, b correction, and c correction methods) were applied to multitemporal Landsat Thematic Mapper data (bands 1-5 and 7) collected in different periods of the growing season (April, June, and July) of a mixed deciduous forest area (340 ha) in the northern Apennines. The effectiveness of the models at removing topographic control, preserving internal data variability, and consistently normalizing radiance for flat pixels from band to band and image to image was evaluated. The entirely empirical b correction outperformed the other considered methods without relying on any photometric function. [ABSTRACT FROM AUTHOR]

Presents the results of the research carried out at the European Microwave Signature Laboratory of the Joint Research Centre of Ispra, Italy for validating electromagnetic models. Description of the three experimental dielectric models; Electromagnetic modeling; Conclusion.