P. Haghighatmehr; M. J. Valadanzouj; R. Tajik; S. Jabari; M. R. Sahebi; R. Eslami; M. Ganjiyan; M. Dehghani
Abstract
A large area in Hashtgerd plain, in southwest of Tehran, is subject to the land subsidence induced by overexploitation of groundwater. In this paper, in order to study the subsidence SAR interferometry (InSAR) and global positioning system (GPS) are used. The small baseline subset (SBAS) algorithm is ...
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A large area in Hashtgerd plain, in southwest of Tehran, is subject to the land subsidence induced by overexploitation of groundwater. In this paper, in order to study the subsidence SAR interferometry (InSAR) and global positioning system (GPS) are used. The small baseline subset (SBAS) algorithm is used for deformation time series analysis. Time series analysis is performed using 6 interferograms calculated from 4 ENVISAT ASAR data spanning 4 months in 2008. A smoothing constraint that reduces the atmospheric noise, unwrapping and orbital errors whereas it preserves the non-linear deformation features is added to the least-squares solution. The time series results revealed that the area is subsiding continuously. Mean LOS deformation velocity map obtained from time series analysis demonstrated a considerable subsidence rate of 47 (mm/month). In order to assess the time series analysis results a dense GPS network consisting of 18 measuring stations is then established. The network design is carried out based on the subsidence spatial pattern extracted from an interferogram calculated from radar data of 2003-2004. The GPS stations are collecting the data simultaneously with radar data acquisitions. Horizontal and vertical components of the subsidence are extracted from GPS measurements. The comparison of InSAR and GPS time series shows the high compatibility of the results demonstrating the high performance of InSAR technique.
S. Adham Khiabani; M. R. Mobasheri; M. J. Valadanzoej; M. Dehghani
Abstract
SAR interferometry has shown its abilities in measuring the surface deformation in various applications. Atmospheric signals as an important factor affecting the interferometric measurements have temporally uncorrelated and complicated behavior. In this paper, a model based on the error source is presented ...
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SAR interferometry has shown its abilities in measuring the surface deformation in various applications. Atmospheric signals as an important factor affecting the interferometric measurements have temporally uncorrelated and complicated behavior. In this paper, a model based on the error source is presented to reduce the atmospheric contributions on the interferometric measurements in Mashhad subsidence area. In this model, the Full-Resolution (RF) MODIS data and meteorological information were used in order to estimate the water vapor and reduce the pressure effect, respectively. Moreover, water drops as well as the clouds effects were considered in the proposed model. Utilizing error propagation, model error was estimated as 7.2 mm. The Root Mean Square Error (RMSE) as a quantitative comparison between GPS measurements and interferometric results showed an improvement from 9 mm (before atmospheric correction) to 2 mm after applying the correction model.
M. Dehghani; S. Dehghani; V. Ahmadi; A. Zavarei
Abstract
Two stratigraphic sections of Kazhdumi Formation were selected form Sivand (165m.) and Kuh-e-khanekat (108m.) Areas for Pelecypoda avd Echinoides study. Recognized taxones of Bivalvia and Echinoides are following as: Neithea striatocostata, Exogyra undata, Isocardia aff. neglecta, Astarte sp., Opis sp., ...
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Two stratigraphic sections of Kazhdumi Formation were selected form Sivand (165m.) and Kuh-e-khanekat (108m.) Areas for Pelecypoda avd Echinoides study. Recognized taxones of Bivalvia and Echinoides are following as: Neithea striatocostata, Exogyra undata, Isocardia aff. neglecta, Astarte sp., Opis sp., Leptosolen sp.,Trigonia crenulifera, Exogyra flabellata ,Salenidia boulei, Pliotoxaster cf. lyonsi ,Epiaster whitei, Inoceramus sp.Assemblage- zones of the mentioned taxones and comparison of them with accompanied zones (foraminifers), age of studied sediments is Albian to Early Cenomanian.
M. Forouzanfar; H. Abrishami-Moghaddam; M. Dehghani
Abstract
Despite the wide application of SAR images in lineaments extraction, DEM generation and displacements determination, their radiometric quality and interpretability is degraded due to the presence of a multiplicative noise called speckle. Therefore, the enhancement of SAR images is an important step before ...
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Despite the wide application of SAR images in lineaments extraction, DEM generation and displacements determination, their radiometric quality and interpretability is degraded due to the presence of a multiplicative noise called speckle. Therefore, the enhancement of SAR images is an important step before using them in any application. In this paper, a new image enhancement method tailored to SAR images is proposed. In this method, the logarithmically transformed SAR image is decomposed using the dual-tree complex wavelet transform (DTCWT).In order to effectively extract the wavelet interscale dependencies, the signal component of wavelet coefficients is modeled with an isotropic stable distribution, while the noise component is approximated using an isotropic Gaussian model. A bivariate Bayesian estimator is then designed to effectively remove speckle from noisy coefficients in the complex wavelet domain. Both quantitative and qualitative comparisons of the proposed method with new speckle reduction methods, demonstrate its higher performance in speckle reduction from SAR images
H. Fattahi; M. J. Valadan Zouj; M. R. Mobasheri; M. Dehghani
Abstract
Interferometric Synthetic Aperture Radar (InSAR) technique using phase information has demonstrated its abilities in topographic mapping and measuring surface deformation with the precision of meter and sub-centimeter, respectively in a very high spatial resolution. However, ...
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Interferometric Synthetic Aperture Radar (InSAR) technique using phase information has demonstrated its abilities in topographic mapping and measuring surface deformation with the precision of meter and sub-centimeter, respectively in a very high spatial resolution. However, various limiting factors such as spatial and temporal decorrelation, atmospheric effects and thermal noise of the radar sensor introduce different types of noise into the interferograms, which makes the phase unwrapping too difficult to obtain the accurate results. In this study, an algorithm for noise suppression is presented based on wavelet transform in the complex domain. The high-frequency data due to the phase jumps is not appeared in the complex domain. Therefore, the wavelet coefficients obtained in the complex domain include mostly the noise. The wavelet coefficients of the noisy interferogram are then filtered using the threshold computed from the related wavelet band. In comparison with the other noise reduction methods such as multi-look processing and those based on Fourier transform in small windows, the proposed algorithm can reduce the noise while keeping the spatial resolution without the need for windowing the interferogram. Quantitative and qualitative evaluations of the results obtained by the new method applied on the simulated and real noisy data show high performance of the wavelet transform in noise reduction.
M. Dehghani; M. J. Valadan Zouj; A. Mansourian
Abstract
study several 2D and 3D math models have been tested in order to correct slant range SAR data geometrically. Some of these models consider the imaging geometry at the time of imaging while the others relate the ground space to the image one by mathematical polynomials. The images used here are 3 ENVISAT ...
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study several 2D and 3D math models have been tested in order to correct slant range SAR data geometrically. Some of these models consider the imaging geometry at the time of imaging while the others relate the ground space to the image one by mathematical polynomials. The images used here are 3 ENVISAT ones of Bam area. In order to extract the 3D GCPs, a topographic map with a scale of 1:25000 and SRTM DEM were used. The 2D math models used in this study include Global polynomial, Point wise, Piece wise and Projective while the 3D models are DLT and Rigorous SAR model. Since the images used in this study were originally ordered for interferometry studies, their baseline is so small that the precision of 3D coordinates extraction is not satisfactory enough. However, the results of 2D models are much better.