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Methods to assess ultrasound backscatter anisotropy from clinical array transducers have recently been developed. However, they do not provide information about the anisotropy of microstructural features of the specimens. This work develops a simple geometric model, referred to as the secant model, of backscatter coefficient anisotropy. Specifically, we evaluate anisotropy of the frequency dependence of the backscatter coefficient parameterized in terms of effective scatterer size. We assess the model in phantoms with known scattering sources and in a skeletal muscle, a well-known anisotropic tissue. We demonstrate that the secant model can determine the orientation of the anisotropic scatterers, as well as accurately determining effective scatterer sizes, and it may classify isotropic versus anisotropic scatterers. The secant model may find utility in monitoring disease progression as well as characterizing normal tissue architectures. [ABSTRACT FROM AUTHOR]

The multi-scale interaction between combustion and turbulence is of great importance in modifying the small-scale flame structure and kinetic energy, especially in swirling flames under practical conditions. In the present study, direct numerical simulation of swirling partially premixed flame is conducted within a model combustor under gas turbine conditions. The reactive flow is compared to the corresponding non-reactive one to investigate the influence of combustion on the scaled kinetic energy transport. Kinetic energy spectra demonstrate that the turbulent kinetic energy is reduced in the dissipative subrange while enhanced in the energetic one by the flame. The critical scale is located in the inertial subrange and close to the estimated turbulent flame thickness. Filtering analyses show that the resolved-scale kinetic energy is augmented by the increased large-scale pressure-gradient work in the reactive flow, while the subgrid-scale kinetic energy is attenuated by the enhanced small-scale viscous dissipation. The backscatter prevails in the heat release regions when the filter size is larger than the laminar flame thickness, and this effect decreases with the swirling flow developing downstream. The interaction between the kinetic energy flux and the local dilatation as well as the subgrid-scale pressure-gradient work is also investigated to achieve a comprehensive understanding about the effects of combustion on the backscatter. [ABSTRACT FROM AUTHOR]

Oil spills, detected by SAR sensors as dark areas, are highly effective marine pollutants that affect the ocean surface. These spills change the water surface tension, attenuating capillary gravitational waves and causing specular reflections. We conducted a case study in the Persian Gulf (Arabian Sea to the Strait of Hormuz), where approximately 163,900 gal of crude oil spilled in March 2017. Our study examined the relationship between oil weathering processes and extracted backscatter values using zonal slices projected over SAR-detected oil spills. Internal backscatter values ranged from −22.5 to −23.5, indicating an oil chemical binding and minimal interaction with seawater. MEDSLIK-II simulations indicated increased oil solubilization and radar attenuation rates with wind, facilitating coastal dispersion. Higher backscatter at the spill edges compared to the core reflected different stages of oil weathering. These results highlight the complex dynamics of oil spills and their environmental impact on marine ecosystems. • Marine oil spill detection with SAR images reveals significant backscatter variation. • Novel method using zonal slices to extract SAR backscatter values over oil spills. • Characterization of oil weathering stages using SAR backscatter changes. • Wind-driven oil solubilization is demonstrated in MEDSLIK-II simulations. • Different oil spill backscatter patterns indicating distinct weathering processes. [ABSTRACT FROM AUTHOR]

Visible light backscatter (VLB) is an innovative passive transmission paradigm to enable ultra low-power communication and localization for the Internet of Things (IoT), overcoming some limitations of conventional active visible light communication (VLC) as well as active/passive radio-frequency (RF) systems. In this paper, we provide a survey of VLB-based techniques and briefly discuss their applications in healthcare applications. After describing the principles of operation and the main enabling technologies, we survey the existing VLB techniques according to several features, discussing their merits and limitations. Finally, we introduce some open challenges in this area, by delineating future research directions. [ABSTRACT FROM AUTHOR]

The marine acoustic techniques are powerful tools to investigate and identify the seabed objects by applying different processing and interpretation steps. Two types of marine acoustic imaging techniques used in this study; Side Scan Sonar (SSS) that mapping seabed features and identifies the objects on it, and Sub-Bottom Profiling (SBP) that providing information about sediment thicknesses and stratigraphic structure. The integration between these two marine acoustic techniques, as well as, ground truth data obtained from an underwater camera, was used to distinguish seabed objects; coastal boulder accumulations that are documented along the western Mediterranean coast of Egypt. The study and analysis of the collected data demonstrated that: the combination between side scan sonar, chirp sub-bottom profiling systems, and ROV images can successfully distinguish different types of objects. Generally, objects observed from SSS are indicated in the SBP as weak backscatter curves. The case study results, from analysis of SBP with ROV image to the object detected by SSS utilized three objects making a shadow in SSS seabed: boulder, hard substrate, and seagrass. The integration of these techniques resulting specifies the location of the geo-hazards area. [ABSTRACT FROM AUTHOR]

The Alamein New City is one of the newly established capital cities in Egypt. The study of the offshore extension is important to define the morpho-sedimentary seafloor features and evaluate the structure of the seafloor, sand resources, and the quantities of sediments that are responsible for beach renourishment. To achieve the purpose of the study, the marine acoustic geophysical techniques (MBES, SSS, and SBP) with video-camera attached in the ROV as a ground truth tool, were used. That has proven to be extremely powerful techniques in coastal applications. The integration of the marine geophysical data obtained from the bathymetric, shallow seismic surveys, and the validity of these data that was confirmed by SSS backscatter sonograph, in addition, the images obtained by using the ROV, divided the study area into three main zones. The southern zone (Z1) was rugged, which coincided with sandy mounds in the area, and has gradual backscatter strength from high to moderate with the direction of the prevailing current describing the rugosity of sand ripple. This zone has characterized by the thickest layer of sediment in the study area. Whereas the middle zone (Z2) showed the highest values of rugosity due to the slope where the ridge exists and has complex backscatter strength with finer thick of sediment. The northern zone (Z3) was characterized mostly by intermediate rugosity and gradual backscatter strength from high to moderate aligned with the direction of the current, describing the rugosity of sand ripple. The northern zone has the second thickest layer of sediment. The gentle sloping of the seafloor with the existence of the mounds and the submerged ridge are allowing the waves to break and scatter their energy provide natural protection for the beaches of Alamein New City. [ABSTRACT FROM AUTHOR]

This paper introduces and investigates the performance of a system where an unmanned aerial vehicle (UAV) is utilized to assist terrestrial backscattering devices (BDs) in wireless energy charging and data transmission. The UAV task is data collection through the backscatter communication with finite block length. To assess performance, the study not only considers energy efficiency (EE) but also derives closed-form expressions for age-of-information (AoI). The block error rate (BLER) expression is approximated using Gaussian-Chebyshev quadrature and the first-order Riemann integral. Furthermore, the optimization problem is solved to maximize EE and minimize transmit power through a search algorithm. Both EE and spectral efficiency (SE) are investigate via the number of transmission bits. The analytical and simulation results show that the optimized EE and minimum transmit power of UAV can be obtained by selecting an appropriate packet length and UAV altitude. Besides, the Rician factor K also has a significant impact on BLER of the considered system. Finally, the study points out that the system performance is strongly influenced by factors such as the utilized bandwidth, the specific operating environments, and the elevation angle of UAV. [ABSTRACT FROM AUTHOR]

• Insufficient scattering material results in published B w values that overestimate scatter. • An algorithm was developed for calculating backscatter in situations with reduced scattering medium. • Model validation by comparison with published data, Monte Carlo simulations and film measurements. Dosimetry protocols for superficial X-rays prescribe the determination of kerma on the surface of a phantom through the use of a backscatter factor (B w) that accounts for the effect of phantom scatter. B w values corresponding to full-scatter phantoms are provided by these protocols. In practice, clinical situations arise wherein there is insufficient scattering material downstream, resulting in published B w values that overestimate the amount of occurring scatter. To provide an accurate dose calculation the backscatter values need to be corrected for any reduction in scattered radiation. Estimating the change of B w in situations with incomplete backscatter has previously been achieved by direct measurements or Monte Carlo modelling. For increasing the accuracy of clinical dosimetries, we developed a physical model to deduce an algorithm for calculating backscatter factors in situations with reduced downstream scattering medium. The predictions of the model were validated by comparison with published data, Monte Carlo simulations and film-based measurements for beams with a half-value layer of 0.8, 2 and 4 mm Al. Our algorithm accurately predicts the effect of partial scatter conditions with suitable precision. Its reliability, combined with the simplicity of calculation, makes this methodology suitable to be incorporated into routine clinical dosimetry. The algorithm's underlying physical model provides an intuitive understanding of the effects of field size and beam energy on backscatter reduction, permitting a rational management of this effect. [ABSTRACT FROM AUTHOR]

This study aims to provide a recent seabed characteristic of ridges along the eastern coast of Alexandria on the Egyptian Mediterranean Sea. Side scan sonar was used for acoustic imaging and Quester Tangent Corporation (QTC) VIEW for acoustic signal survey. ROV was applied to detailed video survey and sediment sampling to provide ground truth data. The integration between acoustic signal classes and the acoustic images can divided the study area into three acoustic categories; 1) weak backscatter corresponds to very fine sand to silt sediments, 2) strong backscatter confined to coarse to medium sand, and 3) isolated reflections, which appear widespread along the whole study area and represent two discrete parallel discontinuous hard limestone ridges. These discrete parallel ridges are found to be trending parallel to the coastline. A seabed feature map for the study area is obtained from the integration of output results of side scan sonar backscatter analysis with the QTC acoustic classification and ground-truthing using ROV and grab sampler. The high resolution of acoustic image help to detect the variation of the wavelength and amplitude of sand ripples in the study area. [ABSTRACT FROM AUTHOR]

Abstract During the bathymetry investigation of the continental margin of the Eastern Mediterranean, several submarine canyons have been discovered crossing the continental shelves and slopes of Lebanon within depths ranging from 80 to 1400 m. These canyons display a relevant variability in their geometry, morphology and sedimentary processes. The continental margin of the Levant, offshore Lebanon, shows a young tectonically active shelf to slope setting, which probably creates a drainage mechanism for the sediment in form of mass movement and slumping. Using high resolution bathymetric data derived from full multi-beam coverage, this study aimed to highlight the main governing factors which contributed to the evolution and differentiation of the western Lebanese submarine canyons. The research focused on the Gulf of Jounieh where tectonic control is more evident and submarine landslides, retrograding on a steep slope, control its evolution. In addition, tributaries and gullies mapped in the Gulf of Jounieh, developed on a less steep substrate and display sinuous to meandering paths. In their formation, a relevant role of coastal/shelf sedimentary sand input down slope and turbidity processes were noticed. The superficial failures are mainly located along the walls of Jounieh and Nahr El Kalb submarine canyons eroding the continental slope. The slope angle is proposed as an important factor controlling the location and volume of submarine failures. Generally large scars are located at the base of the continental slope, between 800 and 1200 m of water depth. Their location correlates with the presence of faults that are also areas of high earthquake activity. Based on the above morphology investigations and despite their apparent steadiness, results suggest that the Jounieh and Nahr El Kalb submarine canyons may be considered a model of canyons eroding by turbidity currents. It demonstrates, as well, how canyons in active margins, like the Lebanese continental margin, fail to reach steady state because of a continuous adjustment to perturbations associated with tectonic displacements and base-level change. [ABSTRACT FROM AUTHOR]

Details about the spatial extent of rice cultivation in different seasons are essential for ensuring global food security as well as addressing environmental issues and climate change. This study aims to introduce a novel approach to discriminate between different rice cultural types and subtypes and identify their optimum stages to represent crop growth profiles using Synthetic Aperture Radar (SAR) data. Dense time series Sentinel-1 SAR backscatter data were analyzed at 12 days intervals throughout the growth period of summer and kharif rice. Statistical analysis using ANOVA at 5% level of significance was conducted to identify the critical stages of discrimination for all cultural types and subtypes. Knowledge-based decision tree algorithm was employed to classify all major types of rice grown during summer and kharif season. A comprehensive analysis revealed significant variations in backscatter profiles among different rice types. The most critical period for effectively distinguishing between various rice cultural types and subtypes was found to be from transplanting to tillering stage. Decision tree algorithm was able to discriminate between rice cultural types and subtypes with high overall accuracy and Kappa coefficient, viz., 94.74% and 0.94 for summer rice and 91.80% and 0.90 for kharif rice, respectively. The findings of this study revealed that C-band co and cross-polarized Sentinel-1 data have the potential to detect differences between different cultural types and subtypes of rice and, therefore, will be helpful in crop growth monitoring and agro-ecological change detection in the cultivation pattern. • First attempt to differentiate various rice cultural types and subtypes using SAR backscatter data. • The novelty of statistically comparing all cultural types and subtypes together is presented. • Critical stages of discrimination were determined statistically for all rice types. • Transplanting to tillering was the most crucial period for discrimination. • High accuracy and kappa coefficients were found to be consistent across most of the cultural types and subtypes. [ABSTRACT FROM AUTHOR]

In this study, the coefficient of variation (CV) is introduced as a unitless statistical measurement for the classification of croplands using synthetic aperture radar (SAR) data. As a measurement of change, the CV is able to capture changing backscatter responses caused by cycles of planting, growing, and harvesting, and thus is able to differentiate these areas from a more static forest or urban area. Pixels with CV values above a given threshold are classified as crops, and below the threshold are non-crops. This paper uses cross-polarized L-band SAR data from the ALOS PALSAR satellite to classify eleven regions across the United States, covering a wide range of major crops and climates. Two separate sets of classification were done, with the first targeting the optimum classification thresholds for each dataset, and the second using a generalized threshold for all datasets to simulate a large-scale operationalized situation. Overall accuracies for the first phase of classification ranged from 66%–81%, and 62%–84% for the second phase. Visual inspection of the results shows numerous possibilities for improving the classifications while still using the same classification method, including increasing the number and temporal frequency of input images in order to better capture phenological events and mitigate the effects of major precipitation events, as well as more accurate ground truth data. These improvements would make the CV method a viable tool for monitoring agriculture throughout the year on a global scale. [ABSTRACT FROM AUTHOR]

A Phase 3 clinical study demonstrated that the addition of 200 kHz Tumor Treating Fields (TTF) to temozolomide in the post-radiation (RT) phase of therapy in newly diagnosed glioblastoma increases progression free and overall survival (resulting in FDA and European Union approval). Preclinical studies have demonstrated the ability of TTF to act as a radiosensitizer, suggesting concurrent TTF and RT may have clinical utility. The removal and replacement of TTF transducer arrays from the scalps of patients on a daily basis, i.e., just before and after RT treatments, would be extremely cumbersome. Based on these considerations, phantom studies of the effect of Optune (TM) transducer arrays on radiation dose distribution were performed to evaluate the feasibility of leaving arrays in place during RT. Film measurements were performed using Gafchromic EBT3 film and an Epson 11000XL scanner. Film calibration was done based on the ratio of the red to blue color channel data. A Siemens Oncor linear accelerator operating at 6 MV, 10 cm × 10 cm field size, and 100 cm source-to-film distance was used for all measurements. For each exposure, two films were stacked, providing planes of measurement that were ∼0.1 and 0.4 mm in depth. Data accrued demonstrated that radiation attenuation should not be a clinically significant issue. However, TTF transducer arrays were found to cause both a radiation bolus effect, as well as an increased exit dose effect. These studies predict increased skin toxicity, which merits significant caution for further clinical development of this combination. [ABSTRACT FROM AUTHOR]

Utilizing remote sensing techniques to extract soil properties can facilitate several engineering applications for large-scale monitoring and modeling purposes such as earthen levees monitoring, landslide mapping, and off-road mobility modeling. This study presents results of statistical analyses to investigate potential correlations between multiple polarization radar backscatter and various physical soil properties. The study was conducted on an approximately 3 km long section of earthen levees along the lower Mississippi river as part of the development of remote levee monitoring methods. Polarimetric synthetic aperture radar imagery from UAVSAR was used along with an extensive set of in situ soil properties. The following properties were analyzed from the top 30–50 cm of soil: texture (sand and clay fraction), penetration resistance (sleeve friction and cone tip resistance), saturated hydraulic conductivity, field capacity, permanent wilting point, and porosity. The results showed some correlation between the cross-polarized (HV) radar backscatter coefficients and most of these properties. A few soil properties, like clay fraction, showed similar but weaker correlations with the co-polarized channels (HH and VV). The correlations between the soil properties and radar backscatter were analyzed separately for the river side and land side of the levee. It was found that the magnitude and direction of the correlation for most of the soil properties noticeably differed between the river and the land sides. The findings of this study can be a good starting point for scattering modelers in a pursuit of better models for radar scattering at cross polarizations which would include more diverse set of soil parameters. [ABSTRACT FROM AUTHOR]

Acoustical geophysical devices depend on sound source to transmit sound waves that reflected, diffracted or scattered off the sea bed. The frequency used by each device controls the output information that related to the sea floor properties. The present study aims to get a recent mapping of the seabed texture mostly related to acoustic imagery, sediment analysis, and video images. High resolution side scan sonar has been used for mapping the seafloor of the Eastern Harbor, Alexandria, Egypt. Four different acoustic patterns were recognized: (a) the pattern of strong backscatter related to coarse sand, (b) the pattern of weak backscatter confined to mud and fine sand, (c) patches of strong and weak backscatter and d) the pattern with isolated reflections that belong to rock outcrops and boulders. The various wavelengths of sand ripples are identifiable that depend on their wavelength and amplitude. The presence of mega ripples in the front of the main EL-Boughaz outlet at the middle of Eastern Harbor indicates bed load transport of sediment during high energy conditions (storms). The current action on the sea bottom produced current ripples which are either straight or sinus. They are usually irregular-crested, showing no bifurcation. [ABSTRACT FROM AUTHOR]

The objective of this study was to examine the contribution of Synthetic Aperture Radar (SAR) images in determining and monitoring some of the main soil properties. In this research, seven SAR images (2 of RADARSAT-1 and 5 of ENVISAT ASAR) were gathered between April and October 2006. An ASTER image of May 2006 that belonged to the same area was also used as an ancillary data. Menemen (Izmir) Plain which covers about 400 km2 of the western part of the Gediz Basin in the west of Turkey was chosen as the area of study. The research was set out to investigate the relationships among some of the soil properties, such as, texture, organic matter, soil salinity, pH and lime content, which are believed to affect backscattering directly. The sigmanought and betanought values of RADARSAT-1 and ENVISAT-ASAR images were calculated in order determine the correlation between the soil properties and radar backscatter. The correlations between soil moisture content, soil texture and backscattering of all SAR images were found significant (r=0.85-0.91). However, no statistically significant relationships were found between backscatter values and organic matter, pH, salt and lime contents of the soils at the test points. [ABSTRACT FROM AUTHOR]

Summary Context To date only single ultrasound parameters were regarded in statistical analyses to characterize osteoarthritic changes in articular cartilage and the potential benefit of using parameter combinations for characterization remains unclear. Objective Therefore, the aim of this work was to utilize feature selection and classification of a Mankin subset score (i.e., cartilage surface and cell sub-scores) using ultrasound-based parameter pairs and investigate both classification accuracy and the sensitivity towards different degeneration stages. Design 40 punch biopsies of human cartilage were previously scanned ex vivo with a 40-MHz transducer. Ultrasound-based surface parameters, as well as backscatter and envelope statistics parameters were available. Logistic regression was performed with each unique US parameter pair as predictor and different degeneration stages as response variables. The best ultrasound-based parameter pair for each Mankin subset score value was assessed by highest classification accuracy and utilized in receiver operating characteristics (ROC) analysis. Results The classifications discriminating between early degenerations yielded area under the ROC curve (AUC) values of 0.94–0.99 (mean ± SD: 0.97 ± 0.03). In contrast, classifications among higher Mankin subset scores resulted in lower AUC values: 0.75–0.91 (mean ± SD: 0.84 ± 0.08). Variable sensitivities of the different ultrasound features were observed with respect to different degeneration stages. Conclusions Our results strongly suggest that combinations of high-frequency ultrasound-based parameters exhibit potential to characterize different, particularly very early, degeneration stages of hyaline cartilage. Variable sensitivities towards different degeneration stages suggest that a concurrent estimation of multiple ultrasound-based parameters is diagnostically valuable. In-vivo application of the present findings is conceivable in both minimally invasive arthroscopic ultrasound and high-frequency transcutaneous ultrasound. [ABSTRACT FROM AUTHOR]

Background: Ultrasound Doppler studies have long been used for quantifying blood flow velocity, and microbubble contrast agents can be used to amplify the Doppler signal. However, the highly nonlinear response of the bubbles to ultrasound can affect measurement accuracy and this has limited their application. Reliable quantitative imaging protocols, however, require the relationship between the response of the microbubble population and the received ultrasound signal to be fully characterized. The complexity of this relationship currently poses a significant barrier to the development of clinically useful techniques. Materials and methods: The experiment was focused at evaluating the attenuation and the backscatter caused by bubbles under varying physiological conditions. Theoretical modeling of the bubble motion was performed for a shelled bubble surrounded by blood cells and then attenuation and the backscatter coefficient (BSC) were calculated theoretically under different conditions. The experiment was divided into the following three parts: variation of temperature, variation of hematocrit, and variation of vessel diameter. In all three parts, attenuation and backscatter caused by lipid bubbles in blood and water were calculated. A 3.5-MHz focused transducer having a focal length of 0.02 m (0.83 in) was used in the experiments. The hydrophone used was a needle hydrophone having a probe of 40 μm. The bubbles used were coated with a lipid shell (Avanti Polar Lipids) and had a concentration of about 107 microbubbles/mL. Results: Attenuation in the sample with blood and bubbles increases from 5 (±0.33) at room temperature to 9.45 (±0.38) at 37°C. For the sample containing blood and bubbles, the BSC increases from 9 × 10−19 m−1/sr (±4.6 × 10−18) at room temperature to 5.3 × 10−18 m−1/sr (±3.6 × 10−17) at 37°C and 5.2 × 10−16 m−1/sr (±3.78 × 10−18) at 40 °C. An increase in attenuation is observed as the hematocrit level is increased; however, the experimental values of the BSC do not change much with change in the hematocrit level. Highest attenuation is seen in the 200-μm vessel of nearly 35 dB/cm (±5) in a sample containing blood and bubbles. The backscatter for the sample containing blood and bubbles increases from 2.5 × 10−19 m−1/sr (±2.8 × 10−20) in the 200-μm vessel to 5.07 × 10−17 m−1/sr (±3.9 × 10−18) in the 4-mm vessel. Conclusion: It has been re-established that as temperature increases from room temperature to body temperature, considerable signal is lost and attenuation and backscatter increase with temperature. Blood cells surrounding the bubbles do alter the attenuation; however, they do not have any effect on the backscatter by the bubbles. This result is different from previous studies, and therefore, more work must be done to validate these results in a more sophisticated experimental setup. Confinement of bubbles inside small vessels affects both attenuation and backscatter. Hence, while designing experiments, care must be taken about choosing the vessels in the body through which the bubble will travel and the parameters must be measured accordingly. [Copyright &y& Elsevier]

Hydroacoustics can be used to assess zooplankton populations, however, backscatter must be scaled to be biologically meaningful. In this study, we used a general model to correlate site-specific hydroacoustic backscatter with zooplankton dry weight biomass estimated from net tows. The relationship between zooplankton dry weight and backscatter was significant (p < 0.001) and explained 76% of the variability in the dry weight data. We applied this regression to hydroacoustic data collected monthly in 2003 and 2004 at two shoals in the Apostle Island Region of Lake Superior. After applying the regression model to convert hydroacoustic backscatter to zooplankton dry weight biomass, we used geostatistics to analyze the mean and variance, and ordinary kriging to create spatial zooplankton distribution maps. The mean zooplankton dry weight biomass estimates from plankton net tows and hydroacoustics were not significantly different (p = 0.19) but the hydroacoustic data had a significantly lower coefficient of variation (p < 0.001). The maps of zooplankton distribution illustrated spatial trends in zooplankton dry weight biomass that were not discernable from the overall means. [ABSTRACT FROM AUTHOR]

Despite a progressive reduction of oil spills caused by the activity of maritime transportation, the latent sources of pollution still exist. Although the harmful impact of heavy fuel oil (HFO) on the marine environment is widely known, many shipwrecks cause contamination of the surrounding areas. In this paper, an approach to monitor the area of the HFO spill around a shipwreck is made using a bottom backscattering strength (BBS) obtained by a multibeam echosounder (MBES). As a case study, the s/s Stuttgart wreck located in the Gulf of Gdansk (Poland) is verified. Two different measurement campaigns have been carried out in shallow waters using low (190 kHz) and high (420 kHz) MBES frequency. The results indicate that the polluted area around s/s Stuttgart was estimated at 49.1 ha, which is around 18.3% more in comparison to the geological surveys made four years earlier. • MBES backscatter is utilized for monitoring and estimating the size of the contaminated area around a known shipwreck. • The case study of the shipwreck lying in the shallow waters in the Gulf of Gdansk (Poland) was selected. • Two operational MBES frequencies (190 kHz and 420 kHz) have been used to investigate how this factor impacts the HFO detection. • The backscatter data were compared with the results collected in 2016 using other survey methods. • The MBES backscatter utilization seems to be a promising solution for periodic monitoring contaminated seabed around high-priority shipwrecks. [ABSTRACT FROM AUTHOR]

Three image-based methods for correcting the effect of changes in incidence angle on backscatter data are proposed and evaluated for AirSAR data of a coastal tropical savanna landscape in Australia's Northern Territory. These correction methods require little field knowledgeand do not assume a linear relationship between SAR backscatter and incidence angle. The correction methods are applied to five independent components of the Stokes Matrix. The results are evaluated using an existing land-cover classification to extract mean backscatter values for individual land-cover classes before and after the correction procedures. It is shown, for the vegetation communities involved, that the slope method provides a successful correction for the amplitudecomponents of the backscatter data. The real and imaginary parts of the co-polarized returns are best corrected using the LUT method. Theproposed correction procedure allowed the use of a maximum-likelihood classification for the discrimination of ten land-cover types with an overall accuracy of 87 percent across the complete swath width of the AirSAR data. [ABSTRACT FROM AUTHOR]