... [4] Ramon, F Satellite radar interferometry for deformation monitoring , ELSEVIER, Remte Se... more ... [4] Ramon, F Satellite radar interferometry for deformation monitoring , ELSEVIER, Remte Sensing of Environment 6(2005) 253 ... 2. Mohammad javad Valadan Zoej Associate Professor Faculty of Geodesy & Geomatics Engineering KN Toosi University of Technology (KNTU) ...
A large allochthonous sheet of Eocene rock salt is forming the Eyvanekey plateau west of Garmsar ... more A large allochthonous sheet of Eocene rock salt is forming the Eyvanekey plateau west of Garmsar along the northern periphery of the Great Kavir basin. This salt extruded over the central plains of Iran, where the southward advancing front of the Alborz Mountains is offset by the ...
Phase unwrapping is one of the most important parts of InSAR techniques. In order to estimate the... more Phase unwrapping is one of the most important parts of InSAR techniques. In order to estimate the grand surface displacements, interferomtric phases modulated between 0 to 2π must be unwrapped. Based on the use of either the conventional method or persistent scatterer (PS), phases will be spread both regularly and irregularly. The phases of PSs can be unwrapped by reducing phases into a regular and continues grid with neatest neighbor interpolation method. In this paper, beside Minimum Cost Flow (MCF) as a global unwrapping method, three local unwrapping methods (Branch-cut, Phase Derivative Variance and Branch cut-Phase Derivative Variance) are introduced as well. These conventional unwrapping approached are implemented on an irregular interferogram processed from Sentinal1A satellite images acquired over the Sirjan basin. At the end, the results of these approaches are assesed with unwraped phase which is resulted in a conventional interferogram unwrapped with MCF method.
ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
By the advent of Persistent Scatterer Interferometry (PSI) time-series analysis, this technique h... more By the advent of Persistent Scatterer Interferometry (PSI) time-series analysis, this technique has demonstrated high performance in producing accurate measurements of ground displacements. However, due to several limitations such as high deformation rate, lack of man-made features and rough topographic characteristic, the efficiency of the PSI significantly decreases. The main goal of this paper is to illustrate the potential of one of the PSI methods namely the Interferometric Point Target Analysis (IPTA) to measure the deformation caused by landslide. The landslide occurs in an area lacking man-made features with rough topography. To this end, 28 Sentinel-1A SLC images spanning from October 14 2014 to October 27 2016, were used to generate single-master interferograms. The PS pixels were identified using amplitude dispersion and spectral diversity criteria. The PS pixels were unwrapped considering a linear model for the deformation behavior in an iterative manner. The residual topography and atmospheric contributions were estimated in each iteration and subtracted from the PS pixels phases. The results were finally compared to those extracted from conventional Small Baseline Subset (SBAS) time series analysis applied on the same datasets. A good agreement existed between two methods in some locations whereas unwrapping errors probably due to improper deformation model were observed in a couple of points. * Corresponding author can also lead to the reliable results. Therefore, in order to evaluate the performance of IPTA in monitoring Kahroud landslide, the results obtained from this method were compared to those achieved by conventional INSAR.
American Journal of Environmental Engineering, 2014
Land subsidence caused by overexploitation of groundwater is a phenomenon that has different deva... more Land subsidence caused by overexploitation of groundwater is a phenomenon that has different devastating effects on environment, infrastructures, buildings, and etc. In this paper the subsidence is modeled by using the water level information of various piezometric wells distributed in the study area, vegetation coverage, and the soil type in Rafsanjan plain located in Kerman province. Also by using the AHP multiple attribute decision making model and use it for each index according to the severity of effect on subsidence, the weights are given and then the information layers were prepared in Geospatial Information System (GIS) using different datasets such as satellite images. The prepared information layers are then integrated assigning a specific weight to each one. In order to evaluate the modeling results, Interferometric Synthetic Aperture Radar (InSAR) as a powerful tool for measuring the ground deformation at high spatial resolution is applied. InSAR technique is a very powerful method to measure the ground surface deformation, displacement, topography and etc by combining radar images which are acquired in different times. An interferogram calculated by subtracting the phase of two radar images contains different phase contribution mainly due to the topography. Therefore, a Digital Elevation Model (DEM) is used for removing the topography effects. There are some limitations in using InSAR technique, but the most important one in the case study area is temporal decorrelation which is the changes of scattering behaviors between 2 radar acquisition times. In his paper 3 ENVISAT ASAR images acquired in 2005 are used to obtain the surface displacement map. The final map produced by modeling is compared with InSAR derived displacement map. The high compatibility of the subsidence model and displacement map extracted from InSAR indicates that weighting of the subsidence factors and their integration are accurately performed.
New generation of space radar sensors with high spatial resolution, heralds the possibility of th... more New generation of space radar sensors with high spatial resolution, heralds the possibility of these images usage for automatic feature extraction, specially road ones related. This study compares road extraction in high resolution radar and optical images. IKONOS and TerraSAR-X images are used for this purpose. In order to make possible the comparison, the images have been coregistered. Then, texture features have been extracted and classified using a back propagation neural network. By comparing the results with reference road network, provided by the operator, for TerraSAR-X and IKONOS images respectively, 46.10 and 57.72 percent for RCC, 46.58 and 93.27 percent for BCC and 0.61 and 0.31 for RMSE were obtained. Comparison of the outputs of two algorithms showed that each of optics and radar images have some defects in road extraction. For example, optical algorithms are sensitive to image parts which have the same texture and spectral features similar to roads such as parkings an...
2008 International Conference on Intelligent Engineering Systems, 2008
Forward kinematics problem of parallel robots is very difficult to solve in comparison to the ser... more Forward kinematics problem of parallel robots is very difficult to solve in comparison to the serial manipulators because of the highly nonlinear relations between joint variables and position and orientation of the end effector. This problem is almost impossible to solve analytically. Numerical methods are one of the common solutions for this problem. But, convergency of these methods is the
ABSTRACT Differential SAR Interferometry (DInSAR) is able to monitor land deformation at submilli... more ABSTRACT Differential SAR Interferometry (DInSAR) is able to monitor land deformation at submillimetre as an areal measurement. DInSAR time series calculates land deformation on every radar acquisition date from all individual interferograms in relation to the first/arbitrary date. These calculations help to monitor long term (trend) as much as short terms (seasonal) variations of the land deformation. This research endeavours to investigate the feasibility of a time series algorithm by use of no consecutive radar data in a case study. The Hashtgerd area of north-western Iran is subject to land subsidence resulting from the overexploitation of groundwater. The only tool for areal monitoring subsidence in this area was the DInSAR method. SAR data covering the Hashtgerd Plain include ENVISAT ASAR and ALOS PALSAR data. The interferograms were calculated by ENVISAT ASAR and ALOS PALSAR raw data. For this calculation, the two-pass DInSAR method was applied. Time series algorithm was worked out in three main steps by use of calculated differential interferograms containing less decorrelation, atmospheric effects, topographic and unwrapping error and other noise sources. Firstly, residual orbital tilts and linear atmospheric effects were reduced from all interferograms by use of a least-squares plane fitting approach. Secondly, all interferograms were corrected in relation to one reference point. Finally, DInSAR time series was elaborated by a least-squares-based method integrated with a finite difference approximation approach. This algorithm was successful to link separate groups of interferograms by use of a proper weighting factor, and reduced a nonlinear part of atmospheric effects. The results of Hashtgerd time series calculations showed a relatively constant long term variation of subsidence about 14 cm/yr, in spite of seasonal variations of subsidence. The time series results of ENVISAT ASAR were compared with the ALOS PALSAR time series results and by GPS data. The DInSAR time series results demonstrated the ability of the time series algorithm applied and the accuracy of the optimal weighting factor determined. German Die Differentielle SAR-Interferometrie (DInSAR) ist eine flächenhaft arbeitende Messmethode, mit der Bodenbewegungen im Millimeter-Bereich bestimmt werden können. Mit DInSAR-Zeitreihen lassen sich Bodenbewegungen überwachen, wobei zu jedem Datum einer Radarmessung die Line-of-Sight (LOS) Entfernungsänderung in Bezug auf ein gewähltes (beliebiges Referenz-) Datum bestimmt wird. Diese Berechnungen helfen, sowohl langfristige Trends als auch kurzzeitige, z. B. saisonale, Variationen der Bodenbewegung abzuleiten. In die sem Beitrag wird die Anwendbarkeit eines Algorithmus zur Zeitreihenauswertung untersucht, wobei für das Untersuchungsgebiet nur unterbrochene Zeitreihen aufeinanderfolgender Radardaten zur Verfügung standen. Die Hashtgerd Ebene im Nordwesten des Iran unterliegt Bodensenkungen, die durch ein übermäßiges Abpumpen des Grundwassers hervorgerufen werden. Die einzige anwendbare Messmethode für eine flächenhafte Überwachung der Bodensenkungen in diesem Bereich ist das DInSAR-Verfahren. Für das Untersuchungsgebiet sind SAR-Daten (ENVISAT-ASAR und ALOS-PALSAR) verfügbar. Die Interferogramme wurden aus den Rohdaten mit der GAMMA Software berechnet. Bei dieser Berechnung wurde das two-pass-DInSAR Verfahren und ein SRTM-Höhenmodell verwendet. Der Zeitreihenalgorithmus gliedert sich in drei Hauptschritte, wobei nur Interferogramme mit hoher Kohärenz und deutlichem Bodenbewegungs-signal benutzt werden. Im ersten Schritt werden residuale (Orbit-) Trends und großräumige atmosphärische Effekte reduziert, indem in allen Interferogrammen eine mit einer Kleinste Quadrate Schätzung angepasste Trendebene abgezogen wurde. Zweitens wurden alle Interferogramme in Bezug auf einen identischen Referenzpunkt außerhalb des durch Bodenbewegungen beeinflussten Gebietes reduziert. Im dritten Schritt wurde die eigentliche Berechnung der Zeitreihen mit einer Ausgleichungsrechnung auf der Basis einer Finite-Differenzen-Approximation durchgeführt. Die Ergebnisse der Zeitreihenberechnungen zeigten eine relativ konstante langfristige Bodensenkung von etwa 14 cm/Jahr sowie deutliche saisonale Schwankungen der Bodenbewegungen. Die Ergebnisse der ENVISAT-ASAR-Daten-Auswertung wurden den Ergebnissen aus ALOS-PALSAR-Daten sowie GPS-Daten gegenübergestellt. Mit dem vorgestellten Algorithmus konnten auch zeitlich getrennte Blöcke von Interferogrammen durch die Verwendung eines geeigneten Gewichtungsfaktors verbunden sowie ein nichtlinearer Störgrößenanteil (Trend) und atmosphärische Effekte reduziert werden. Die Ergebnisse der DInSAR-Zeitreihenberechnungen belegen die Nutzbarkeit des hier vorgestellten Algorithmus und die Adäquatheit des abgeleiteten Gewichtungsfaktors.
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2013
ABSTRACT The Southwestern Tehran basin is covered primarily by agricultural fields and is subject... more ABSTRACT The Southwestern Tehran basin is covered primarily by agricultural fields and is subjected to significant levels of land subsidence phenomena. Conventional SAR interferometry cannot extract deformation information from the available SAR images due to large spatial baselines and temporal de-correlation. Moreover, the proper Persistent Scatterer interferometry method for a rural area (StaMPS, Stanford method for Persistent Scatterer) cannot efficiently operate in areas with high deformation, such as the Tehran basin, because of unwrapping error caused by temporal aliasing of the signal. Therefore, in this work, a method based on StaMPS is developed to address the unwrapping error in the Tehran basin. In the proposed method, the estimated deformation rate from the wrapped phase and the periodogram approach are used to reduce the likelihood of aliasing, and StaMPS is subsequently applied to the residual phase. The method is applied to ENVISAT ASAR images captured between 2003 and 2008, and the mean precision of the estimated deformation is approximately 2.5 mm/yr. A comparison of the results obtained from the proposed method with those from continuous GPS and leveling measurements demonstrates its efficiency.
2007 IEEE 15th Signal Processing and Communications Applications, 2007
This paper introduces a new wavelet-based speckle reduction method for medical ultrasound images,... more This paper introduces a new wavelet-based speckle reduction method for medical ultrasound images, which extends a recently emerged homomorphic Bayesian technique. The new method exploits interscale dependency of wavelet coefficients. For this purpose, bivariate alpha-stable distributions are proposed, which are able to better capture the heavy-tailed nature of the data. Using this new statistical model, we design a bivariate Bayesian estimator to effectively remove speckle from wavelet coefficients. Better results are obtained using the oriented two-dimensional dual-tree complex wavelet transform (2-D DTCWT) which offers improved directional selectivity and near shift invariance property. To assess the performance of the proposed method, results are compared with some related earlier techniques. Both numerical and visual comparisons indicate improved speckle reduction while preserving structural features, as desired for better diagnosis in medical images.
... [4] Ramon, F Satellite radar interferometry for deformation monitoring , ELSEVIER, Remte Se... more ... [4] Ramon, F Satellite radar interferometry for deformation monitoring , ELSEVIER, Remte Sensing of Environment 6(2005) 253 ... 2. Mohammad javad Valadan Zoej Associate Professor Faculty of Geodesy & Geomatics Engineering KN Toosi University of Technology (KNTU) ...
A large allochthonous sheet of Eocene rock salt is forming the Eyvanekey plateau west of Garmsar ... more A large allochthonous sheet of Eocene rock salt is forming the Eyvanekey plateau west of Garmsar along the northern periphery of the Great Kavir basin. This salt extruded over the central plains of Iran, where the southward advancing front of the Alborz Mountains is offset by the ...
Phase unwrapping is one of the most important parts of InSAR techniques. In order to estimate the... more Phase unwrapping is one of the most important parts of InSAR techniques. In order to estimate the grand surface displacements, interferomtric phases modulated between 0 to 2π must be unwrapped. Based on the use of either the conventional method or persistent scatterer (PS), phases will be spread both regularly and irregularly. The phases of PSs can be unwrapped by reducing phases into a regular and continues grid with neatest neighbor interpolation method. In this paper, beside Minimum Cost Flow (MCF) as a global unwrapping method, three local unwrapping methods (Branch-cut, Phase Derivative Variance and Branch cut-Phase Derivative Variance) are introduced as well. These conventional unwrapping approached are implemented on an irregular interferogram processed from Sentinal1A satellite images acquired over the Sirjan basin. At the end, the results of these approaches are assesed with unwraped phase which is resulted in a conventional interferogram unwrapped with MCF method.
ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences
By the advent of Persistent Scatterer Interferometry (PSI) time-series analysis, this technique h... more By the advent of Persistent Scatterer Interferometry (PSI) time-series analysis, this technique has demonstrated high performance in producing accurate measurements of ground displacements. However, due to several limitations such as high deformation rate, lack of man-made features and rough topographic characteristic, the efficiency of the PSI significantly decreases. The main goal of this paper is to illustrate the potential of one of the PSI methods namely the Interferometric Point Target Analysis (IPTA) to measure the deformation caused by landslide. The landslide occurs in an area lacking man-made features with rough topography. To this end, 28 Sentinel-1A SLC images spanning from October 14 2014 to October 27 2016, were used to generate single-master interferograms. The PS pixels were identified using amplitude dispersion and spectral diversity criteria. The PS pixels were unwrapped considering a linear model for the deformation behavior in an iterative manner. The residual topography and atmospheric contributions were estimated in each iteration and subtracted from the PS pixels phases. The results were finally compared to those extracted from conventional Small Baseline Subset (SBAS) time series analysis applied on the same datasets. A good agreement existed between two methods in some locations whereas unwrapping errors probably due to improper deformation model were observed in a couple of points. * Corresponding author can also lead to the reliable results. Therefore, in order to evaluate the performance of IPTA in monitoring Kahroud landslide, the results obtained from this method were compared to those achieved by conventional INSAR.
American Journal of Environmental Engineering, 2014
Land subsidence caused by overexploitation of groundwater is a phenomenon that has different deva... more Land subsidence caused by overexploitation of groundwater is a phenomenon that has different devastating effects on environment, infrastructures, buildings, and etc. In this paper the subsidence is modeled by using the water level information of various piezometric wells distributed in the study area, vegetation coverage, and the soil type in Rafsanjan plain located in Kerman province. Also by using the AHP multiple attribute decision making model and use it for each index according to the severity of effect on subsidence, the weights are given and then the information layers were prepared in Geospatial Information System (GIS) using different datasets such as satellite images. The prepared information layers are then integrated assigning a specific weight to each one. In order to evaluate the modeling results, Interferometric Synthetic Aperture Radar (InSAR) as a powerful tool for measuring the ground deformation at high spatial resolution is applied. InSAR technique is a very powerful method to measure the ground surface deformation, displacement, topography and etc by combining radar images which are acquired in different times. An interferogram calculated by subtracting the phase of two radar images contains different phase contribution mainly due to the topography. Therefore, a Digital Elevation Model (DEM) is used for removing the topography effects. There are some limitations in using InSAR technique, but the most important one in the case study area is temporal decorrelation which is the changes of scattering behaviors between 2 radar acquisition times. In his paper 3 ENVISAT ASAR images acquired in 2005 are used to obtain the surface displacement map. The final map produced by modeling is compared with InSAR derived displacement map. The high compatibility of the subsidence model and displacement map extracted from InSAR indicates that weighting of the subsidence factors and their integration are accurately performed.
New generation of space radar sensors with high spatial resolution, heralds the possibility of th... more New generation of space radar sensors with high spatial resolution, heralds the possibility of these images usage for automatic feature extraction, specially road ones related. This study compares road extraction in high resolution radar and optical images. IKONOS and TerraSAR-X images are used for this purpose. In order to make possible the comparison, the images have been coregistered. Then, texture features have been extracted and classified using a back propagation neural network. By comparing the results with reference road network, provided by the operator, for TerraSAR-X and IKONOS images respectively, 46.10 and 57.72 percent for RCC, 46.58 and 93.27 percent for BCC and 0.61 and 0.31 for RMSE were obtained. Comparison of the outputs of two algorithms showed that each of optics and radar images have some defects in road extraction. For example, optical algorithms are sensitive to image parts which have the same texture and spectral features similar to roads such as parkings an...
2008 International Conference on Intelligent Engineering Systems, 2008
Forward kinematics problem of parallel robots is very difficult to solve in comparison to the ser... more Forward kinematics problem of parallel robots is very difficult to solve in comparison to the serial manipulators because of the highly nonlinear relations between joint variables and position and orientation of the end effector. This problem is almost impossible to solve analytically. Numerical methods are one of the common solutions for this problem. But, convergency of these methods is the
ABSTRACT Differential SAR Interferometry (DInSAR) is able to monitor land deformation at submilli... more ABSTRACT Differential SAR Interferometry (DInSAR) is able to monitor land deformation at submillimetre as an areal measurement. DInSAR time series calculates land deformation on every radar acquisition date from all individual interferograms in relation to the first/arbitrary date. These calculations help to monitor long term (trend) as much as short terms (seasonal) variations of the land deformation. This research endeavours to investigate the feasibility of a time series algorithm by use of no consecutive radar data in a case study. The Hashtgerd area of north-western Iran is subject to land subsidence resulting from the overexploitation of groundwater. The only tool for areal monitoring subsidence in this area was the DInSAR method. SAR data covering the Hashtgerd Plain include ENVISAT ASAR and ALOS PALSAR data. The interferograms were calculated by ENVISAT ASAR and ALOS PALSAR raw data. For this calculation, the two-pass DInSAR method was applied. Time series algorithm was worked out in three main steps by use of calculated differential interferograms containing less decorrelation, atmospheric effects, topographic and unwrapping error and other noise sources. Firstly, residual orbital tilts and linear atmospheric effects were reduced from all interferograms by use of a least-squares plane fitting approach. Secondly, all interferograms were corrected in relation to one reference point. Finally, DInSAR time series was elaborated by a least-squares-based method integrated with a finite difference approximation approach. This algorithm was successful to link separate groups of interferograms by use of a proper weighting factor, and reduced a nonlinear part of atmospheric effects. The results of Hashtgerd time series calculations showed a relatively constant long term variation of subsidence about 14 cm/yr, in spite of seasonal variations of subsidence. The time series results of ENVISAT ASAR were compared with the ALOS PALSAR time series results and by GPS data. The DInSAR time series results demonstrated the ability of the time series algorithm applied and the accuracy of the optimal weighting factor determined. German Die Differentielle SAR-Interferometrie (DInSAR) ist eine flächenhaft arbeitende Messmethode, mit der Bodenbewegungen im Millimeter-Bereich bestimmt werden können. Mit DInSAR-Zeitreihen lassen sich Bodenbewegungen überwachen, wobei zu jedem Datum einer Radarmessung die Line-of-Sight (LOS) Entfernungsänderung in Bezug auf ein gewähltes (beliebiges Referenz-) Datum bestimmt wird. Diese Berechnungen helfen, sowohl langfristige Trends als auch kurzzeitige, z. B. saisonale, Variationen der Bodenbewegung abzuleiten. In die sem Beitrag wird die Anwendbarkeit eines Algorithmus zur Zeitreihenauswertung untersucht, wobei für das Untersuchungsgebiet nur unterbrochene Zeitreihen aufeinanderfolgender Radardaten zur Verfügung standen. Die Hashtgerd Ebene im Nordwesten des Iran unterliegt Bodensenkungen, die durch ein übermäßiges Abpumpen des Grundwassers hervorgerufen werden. Die einzige anwendbare Messmethode für eine flächenhafte Überwachung der Bodensenkungen in diesem Bereich ist das DInSAR-Verfahren. Für das Untersuchungsgebiet sind SAR-Daten (ENVISAT-ASAR und ALOS-PALSAR) verfügbar. Die Interferogramme wurden aus den Rohdaten mit der GAMMA Software berechnet. Bei dieser Berechnung wurde das two-pass-DInSAR Verfahren und ein SRTM-Höhenmodell verwendet. Der Zeitreihenalgorithmus gliedert sich in drei Hauptschritte, wobei nur Interferogramme mit hoher Kohärenz und deutlichem Bodenbewegungs-signal benutzt werden. Im ersten Schritt werden residuale (Orbit-) Trends und großräumige atmosphärische Effekte reduziert, indem in allen Interferogrammen eine mit einer Kleinste Quadrate Schätzung angepasste Trendebene abgezogen wurde. Zweitens wurden alle Interferogramme in Bezug auf einen identischen Referenzpunkt außerhalb des durch Bodenbewegungen beeinflussten Gebietes reduziert. Im dritten Schritt wurde die eigentliche Berechnung der Zeitreihen mit einer Ausgleichungsrechnung auf der Basis einer Finite-Differenzen-Approximation durchgeführt. Die Ergebnisse der Zeitreihenberechnungen zeigten eine relativ konstante langfristige Bodensenkung von etwa 14 cm/Jahr sowie deutliche saisonale Schwankungen der Bodenbewegungen. Die Ergebnisse der ENVISAT-ASAR-Daten-Auswertung wurden den Ergebnissen aus ALOS-PALSAR-Daten sowie GPS-Daten gegenübergestellt. Mit dem vorgestellten Algorithmus konnten auch zeitlich getrennte Blöcke von Interferogrammen durch die Verwendung eines geeigneten Gewichtungsfaktors verbunden sowie ein nichtlinearer Störgrößenanteil (Trend) und atmosphärische Effekte reduziert werden. Die Ergebnisse der DInSAR-Zeitreihenberechnungen belegen die Nutzbarkeit des hier vorgestellten Algorithmus und die Adäquatheit des abgeleiteten Gewichtungsfaktors.
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2013
ABSTRACT The Southwestern Tehran basin is covered primarily by agricultural fields and is subject... more ABSTRACT The Southwestern Tehran basin is covered primarily by agricultural fields and is subjected to significant levels of land subsidence phenomena. Conventional SAR interferometry cannot extract deformation information from the available SAR images due to large spatial baselines and temporal de-correlation. Moreover, the proper Persistent Scatterer interferometry method for a rural area (StaMPS, Stanford method for Persistent Scatterer) cannot efficiently operate in areas with high deformation, such as the Tehran basin, because of unwrapping error caused by temporal aliasing of the signal. Therefore, in this work, a method based on StaMPS is developed to address the unwrapping error in the Tehran basin. In the proposed method, the estimated deformation rate from the wrapped phase and the periodogram approach are used to reduce the likelihood of aliasing, and StaMPS is subsequently applied to the residual phase. The method is applied to ENVISAT ASAR images captured between 2003 and 2008, and the mean precision of the estimated deformation is approximately 2.5 mm/yr. A comparison of the results obtained from the proposed method with those from continuous GPS and leveling measurements demonstrates its efficiency.
2007 IEEE 15th Signal Processing and Communications Applications, 2007
This paper introduces a new wavelet-based speckle reduction method for medical ultrasound images,... more This paper introduces a new wavelet-based speckle reduction method for medical ultrasound images, which extends a recently emerged homomorphic Bayesian technique. The new method exploits interscale dependency of wavelet coefficients. For this purpose, bivariate alpha-stable distributions are proposed, which are able to better capture the heavy-tailed nature of the data. Using this new statistical model, we design a bivariate Bayesian estimator to effectively remove speckle from wavelet coefficients. Better results are obtained using the oriented two-dimensional dual-tree complex wavelet transform (2-D DTCWT) which offers improved directional selectivity and near shift invariance property. To assess the performance of the proposed method, results are compared with some related earlier techniques. Both numerical and visual comparisons indicate improved speckle reduction while preserving structural features, as desired for better diagnosis in medical images.
Uploads
Papers by M. Dehghani