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Geoscience and Remote Sensing, IEEE Transactions on

Issue 8 • Date Aug. 2002

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Displaying Results 1 - 21 of 21
  • Phase unwrapping for large SAR interferograms: statistical segmentation and generalized network models

    Page(s): 1709 - 1719
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (660 KB) |  | HTML iconHTML  

    Two-dimensional (2-D) phase unwrapping is a key step in the analysis of interferometric synthetic aperture radar (InSAR) data. While challenging even in the best of circumstances, this problem poses unique difficulties when the dimensions of the interferometric input data exceed the limits of one's computational capabilities. In order to deal with such cases, we propose a technique for applying the statistical-cost, network-flow phase-unwrapping algorithm (SNAPHU) of Chen and Zebker (2001) to large datasets. Specifically, we introduce a methodology whereby a large interferogram is partitioned into a set of several smaller tiles that are unwrapped individually and then divided further into independent, irregularly shaped reliable regions. These regions are subsequently assembled into a full unwrapped solution, with the phase offsets between regions computed in a secondary optimization problem whose objective is to maximize the a posteriori probability of the final solution. As this secondary problem assumes the same statistical models as employed in the initial tile-unwrapping stage, the technique results in a solution that approximates the solution that would have been obtained had the full-size interferogram been unwrapped as a single piece. The secondary problem is framed in terms of network-flow ideas, allowing the use of an existing nonlinear solver. Applying the algorithm to a large topographic interferogram acquired over central Alaska, we find that the technique is less prone to unwrapping artifacts than more simple tiling approaches. View full abstract»

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  • Unwrapping ground displacement signals in satellite radar interferograms with aid of GPS data and MRF regularization

    Page(s): 1743 - 1754
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (838 KB)  

    Synthetic aperture radar (SAR) images acquired by radar satellites at different times can be combined into interferograms that reveal information about the change in range from ground to satellite, wrapped into phase fringes corresponding to half the radar wavelength. We describe a methodology that uses Markov random field (MRF) regularization and simulated annealing optimization to unwrap such differential interferograms. Often, repeated Global Positioning System (GPS) geodetic measurements are available in an area covered by interferograms. Here, such repeated GPS observations are used to provide a complementary measurement of the unwrapped change in range at sparse locations. The process of unwrapping interferograms can be initialized and guided with such sparsely located "correct" values. Both interferograms and GPS observations may include several error factors, which are reduced before combining the two observations. GPS-measured range change is used to eliminate residual orbital error. In the unwrapping procedure, a vectorized lowpass filter is used to gain temporarily increased smoother variation of the phase. For the purposes of initializing the unwrapping process, virtual unwrapped interferograms are created by ordinary kriging of GPS-measured range change. The initial interferograms are then optimized further by using MRF regularization that incorporate the assumption of a smoothly varying displacement field and the relationship of the unwrapped images to the GPS observations. A simulated annealing optimization algorithm is used to find an optimal solution of the MRF regularization. The smoothed unwrapped interferograms are then used to construct unwrapped versions of the unfiltered input interferogram. Several additional image analyses methods are used in the optimization process to make the unwrapping more efficient and faster. The unwrapping technique is applied to unwrap interferograms from the Reykjanes Peninsula, in southwest Iceland. View full abstract»

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  • A computationally efficient discrete Backus-Gilbert footprint-matching algorithm

    Page(s): 1865 - 1878
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB) |  | HTML iconHTML  

    A computationally efficient discrete Backus-Gilbert (BG) method is derived that is appropriate for resolution-matching applications using oversampled data. The method builds upon existing BG methods and approximation techniques to create a modified set of BG coefficients. The method in its current form is restricted to a resolution-only minimization constraint, but in the future could be extended to use a simultaneous noise minimization constraint using a generalized singular value decomposition (GSVD) approach. A theoretical one-dimensional intercomparison is performed using a hypothetical sensor configuration. A comparison of the discrete BG method with a nondiscrete BG method shows that the new approach can be 250% more efficient while maintaining similar accuracies. In addition, an SVD approximation increases the computational efficiencies an additional 43%-106%, depending upon the scene. Several quadrature methods were also tested. The results suggest that accuracy improvements are possible using customized quadrature in regions containing known physical data discontinuities (such as along coastlines in microwave imagery data). The ability to recompute the modified BG coefficients dynamically at lower computational cost makes this work applicable toward applications in which noise may vary, or where data observations are not available consistently (e.g. in radio frequency interference contaminated environments). View full abstract»

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  • A simple model for SAR azimuth speckle, focusing, and interferometric decorrelation

    Page(s): 1885 - 1889
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    The phenomenon of speckle in synthetic aperture radar (SAR) images is well known as a characteristic grainy appearance of radar images. Speckle is frequently a significant obstacle to visual interpretations of radar data or target identification. In addition, it is usually the dominant noise source in SAR interferometry, since it is responsible for image decorrelation that degrades interferometric fringes, places severe constraints on orbits, and limits the accuracy of height measurements. This communication deals with the geometric sources of speckle. This conventional picture is extended to the case of vertically separated scatterers, and the formulation that results is applied to the structurally similar topics of azimuth focusing, interferometric decorrelation from defocusing, and atmospheric phase delays. View full abstract»

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  • A group-theoretic analysis of symmetric target scattering with application to landmine detection

    Page(s): 1802 - 1814
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (397 KB) |  | HTML iconHTML  

    Landmines are generally constructed such that they possess a high level of geometric symmetry and are then buried in a manner that preserves this symmetry. The scattered response of such a symmetric target will likewise exhibit the symmetry of the target, as well as the electromagnetic reciprocity exhibited by all scatterers. Group theory provides a mathematic tool for describing geometric symmetry, and it can likewise be used to describe the symmetries inherent in the bistatic scattering from mines. Specifically, group theory can be used to determine specific forms of the dyadic Green's function of symmetric scatterers, such that multiple scattering solutions can be determined from a knowledge of a single bistatic geometry. Likewise, group theory can be used both to determine and analyze degenerate cases, wherein specific bistatic responses can be identified as zero regardless of target size, shape, or material. These results suggest a method for classifying subsurface targets as either symmetric or asymmetric. From the group-theoretic analysis, scattering features can be constructed that are indicative of target symmetry, but invariant with respect to other target parameters such as size, shape, or material. These features provide a physically based, target-independent value to aid in mine detection and/or clutter rejection. To test the efficacy of this idea, an extensive collection of bistatic ground-penetrating radar (GPR) measurements was taken for both a symmetric and an asymmetric target. The two targets were easily discernable using symmetry features only, a result that suggests symmetry features can be effective in identifying subsurface targets. View full abstract»

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  • Digital elevation map generation using VHF-band SAR data in forested areas

    Page(s): 1769 - 1776
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB) |  | HTML iconHTML  

    The paper investigates digital elevation model (DEM) generation based on data from the ultra wideband coherent all radio band sensing (CARABAS) very high frequency (VRF)-band synthetic aperture radar (SAR). The results show excellent capability to penetrate forest areas, i.e., the generated DEMs are found to be close to the true ground height. A conventional DEM, based on stereo photography and surveying, and additional phase differential Global Positioning System (GPS) measurements have been used for comparison. The results in heavily vegetated areas (stem volume up to 600 m3/ha) show a mean height difference of less than 1.5 m and a root-mean-square (rms) error of less than 1.0 in compared to the conventional DEM. Stable backscattering properties allows us to use large baselines in order to obtain high height sensitivity. However, the amount of poor data due to low coherence increases with the increase of the baseline. The optimum baseline which balances these two effects is found to correspond to an incidence angle difference of 4°-8°. View full abstract»

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  • Seasonality extraction by function fitting to time-series of satellite sensor data

    Page(s): 1824 - 1832
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (604 KB) |  | HTML iconHTML  

    A new method for extracting seasonality information from time-series of satellite sensor data is presented. The method is based on nonlinear least squares fits of asymmetric Gaussian model functions to the time-series. The smooth model functions are then used for defining key seasonality parameters, such as the number of growing seasons, the beginning and end of the seasons, and the rates of growth and decline. The method is implemented in a computer program TIMESAT and tested on Advanced Very High Resolution Radiometer (AVHRR) normalized difference vegetation index (NDVI) data over Africa. Ancillary cloud data [clouds from AVHRR (CLAVR)] are used as estimates of the uncertainty levels of the data values. Being general in nature, the proposed method can be applied also to new types of satellite-derived time-series data. View full abstract»

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  • Estimating the effective number of looks in interferometric SAR data

    Page(s): 1733 - 1742
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (645 KB) |  | HTML iconHTML  

    The probability density function (pdf) of the multi-look interferometric phase between two complex synthetic aperture radar (SAR) images is parameterized by the number of looks and the complex correlation coefficient. In practice, adjacent pixels in a real SAR interferogram, are statistically dependent due to filtering, and hence, the number of looks is usually smaller than the number of samples averaged. It has been shown that compensation with an effective number of looks, rather than an intractable rederivation of the pdf, can account for the statistical dependence. This paper addresses the challenge of how to determine a suitable value for the effective number of looks. It is shown that an optimum value can be found via a maximum-likelihood estimator (MLE) based on the interferometric phase pdf. However, since such an MLE is computationally intensive and numerically unstable, an estimator based on the method of moments (MoM) possessing similar fidelity is proposed. MoM is fast and robust and can be used in operational applications, such as determining constant false alarm rate (CFAR) detection thresholds for moving-target detection in SAR along-track interferometry. View full abstract»

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  • An automated, dynamic threshold cloud-masking algorithm for daytime AVHRR images over land

    Page(s): 1682 - 1694
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (466 KB) |  | HTML iconHTML  

    An operational scheme for masking cloud-contaminated pixels in Advanced Very High Resolution Radiometer (AVHRR) daytime data over land is developed, evaluated, and presented. Dynamic thresholding is used with channel 1 reflectance data, channel 3 minus channel 4 temperature difference data, and channel 4 minus channel 5 temperature difference data to automatically create a cloud mask for a single image. The dynamic thresholds can be applied in two different ways: to each pixel individually and to classes of pixels determined by an unsupervised minimum Euclidian distance classifier. The dynamic threshold cloud-masking (DTCM) algorithm presented in this study is used to produce cloud masks based on three different configurations: two channels and individual pixels, three channels and individual pixels, and three channels and classes of pixels. These cloud masks are compared with control masks that were created by visual inspection. The results from the clouds from AVHRR (CLAVR) algorithm and the cloud and surface parameter retrieval (CASPR) algorithm are also compared with the control masks. The results of the comparisons indicate that DTCM, applied on a pixel-by-pixel basis, correctly identifies more clear pixels than CASPR or CLAVR while correctly identifying a comparable or higher number of cloud-contaminated pixels. View full abstract»

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  • Polarization of measurement for microwave temperature sounding of the mesosphere

    Page(s): 1669 - 1681
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (523 KB) |  | HTML iconHTML  

    This paper examines microwave measurement polarization for mesospheric temperature profile retrieval on a global basis, for which forthcoming satellite instruments are tasked. Retrieval performances at circular, horizontal, and vertical polarization are mapped across the range of geomagnetic conditions (field strength and view orientation) and are related to the impact of Zeeman line splitting on temperature channel weighting functions. Retrieval performance is hampered by conditions that cause clusters and gaps with respect to the heights at which the weighting functions peak, and this may be a greater detriment to sounding performance than the double-peaking of weighting functions that has been previously identified as a pitfall of sounding in linear polarization. Each of the measurement polarizations was better than the other two under some of the geomagnetic conditions. An orbit simulator was used to document the frequency of occurrence of each of the geomagnetic viewing conditions. With respect to overall global performance, circular polarization was found to be the best choice, regardless whether conical or cross-track scanning is used. Between the linear polarizations, vertical was preferable to horizontal for conical sounding at fine spectral resolution. View full abstract»

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  • Hierarchical network flow phase unwrapping

    Page(s): 1695 - 1708
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (566 KB) |  | HTML iconHTML  

    The well-studied interferometric synthetic aperture radar (InSAR) problem for digital elevation map generation involves the derivation of topography from the radar phase. The topography is a function of the full phase, whereas the measured phase is known modulo 2π, necessitating the process of recovering full phase values via phase unwrapping. This mathematical process becomes difficult through the presence of noise and phase discontinuities. This paper is motivated by research which models phase unwrapping as a network-flow minimization problem. A major limitation is that often a substantial computational effort is required to find solutions. Commonly, these phase images are huge (≫10 million pixels), and obviously the sheer size of the problem itself makes phase unwrapping challenging. This paper addresses the development of a computationally efficient hierarchical algorithm, based on a "divide-and-conquer" approach. We have shown that the phase-unwrapping problem can first be partitioned into independent phase-unwrapping subproblems, which can further be recombined to produce the unwrapped phase. Interestingly, the recombination step itself can be interpreted as an unwrapping problem, for which a modified network-flow solution applies! In short, this paper develops a parallelization of the network-flow algorithm, allowing images of virtually unlimited size to be unwrapped and leading to dramatic decreases in the algorithm execution time. View full abstract»

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  • SAR-retrieved wind in polar regions-comparison with in situ data and atmospheric model output

    Page(s): 1720 - 1732
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (886 KB)  

    European remote sensing (ERS) satellites synthetic aperture radar (SAR) wind retrievals using CMOD-IFR2 are, for the first time, retrieved in the marginal ice zone (MIZ) and in Arctic coastal areas and compared with in situ observations from reseach vessels (RVs) and output from a high-resolution atmospheric model. The root mean squares (rms) of the comparisons were 1.6 m s-1 and 2 m s-1, respectively. The spatial variation of the SAR wind fields established a decrease in wind speed close to the ice edge for the late summer situations where the wind was along the ice edge with the ice to the left. This decrease is believed to be due to changes in atmospheric stability, possibly through development of an internal boundary layer caused by the cold ice cover and melt water. Lower wind speed near the ice edge is confirmed by the atmospheric model and the in situ observations. Furthermore, good results are obtained from SAR wind retrieval in leads when compared with model output during a cold-air outbreak. Routine measurements in the MIZ are useful for estimating the wind stress, and therefore SAR may play an important role in this region. Finally, the identification of a jet out from Hinlopen Strait in the Svalbard region and low wind wakes along the coast in the SAR-retrieved wind field is confirmed by in situ observations as the RV moves through the region. The jet is also confirmed by the atmospheric model, which is able to reproduce the situation. View full abstract»

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  • An ultrafast wide-band millimeter-wave (MMW) polarimetric radar for remote sensing applications

    Page(s): 1777 - 1786
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (426 KB) |  | HTML iconHTML  

    With the advent of high-frequency radio frequency (RF) circuits and components technology, millimeter-wave (MMW) radars are being proposed for a large number of military and civilian applications. Accurate and high-resolution characterization of the polarimetric radar backscatter responses of both clutter and man-made targets at MMW frequencies is essential for the development of radar systems and optimal detection and tracking algorithms. Toward this end, a new design is developed for ultrafast, wide-band, polarimetric, instrumentation radars that operate at 35 and 95 GHz. With this new design, the complete scattering matrix of a target (magnitude and phase) can be measured over a bandwidth of 500 MHz in less than 2 μs. In this paper, the design concepts and procedures for the construction and calibration of these radars are described. In addition, the signal processing algorithm and data-acquisition procedure used with the new radars are presented. To demonstrate the accuracy and applicability of the new radars, backscatter measurements of certain points and distributed targets are compared with their analytical radar cross section (RCS) and previously measured σ° values, respectively, and good agreements are shown. These systems, which can be mounted on a precision gimbal assembly that facilitates their application as high-resolution imaging radar systems, are used to determine the MMW two-way propagation loss of a corn field for different plant moisture conditions. View full abstract»

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  • An algorithm using visible and 1.38-μm channels to retrieve cirrus cloud reflectances from aircraft and satellite data

    Page(s): 1659 - 1668
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (499 KB) |  | HTML iconHTML  

    The Moderate Resolution Imaging Spectro-Radiometer (MODIS) on the Terra spacecraft has a channel near 1.38 μm for remote sensing of high clouds from space. The implementation of this channel on MODIS was primarily based on previous analysis of hyperspectral imaging data collected with the Airborne Visible Infrared Imaging Spectrometer (AVIRIS). We describe an algorithm to retrieve cirrus bidirectional reflectance using channels near 0.66 and 1.38 μm. It is shown that the apparent reflectance of the 1.38-μm channel is essentially the bidirectional reflectance of cirrus clouds attenuated by the absorption of water vapor above cirrus clouds. A practical algorithm based on the scatterplot of 1.38-μm channel apparent reflectance versus 0.66-μm channel apparent reflectance has been developed to scale the effect of water vapor absorption so that the true cirrus reflectance in the visible spectral region can be obtained. To illustrate the applicability of the present algorithm, results for cirrus reflectance retrievals from AVIRIS and MODIS data are shown. The derived cirrus reflectance in the spectral region of 0.4-1 μm can be used to remove cirrus contamination in a satellite image obtained at a visible channel. An example of such an application is shown. The spatially averaged cirrus reflectances derived from MODIS data can be used to establish global cirrus climatology, as is demonstrated by a sample global cirrus reflectance image. View full abstract»

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  • An automated parallel image registration technique based on the correlation of wavelet features

    Page(s): 1849 - 1864
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (622 KB) |  | HTML iconHTML  

    With the increasing importance of multiple multiplatform remote sensing missions, fast and automatic integration of digital data from disparate sources has become critical to the success of these endeavors. Our work utilizes maxima of wavelet coefficients to form the basic features of a correlation-based automatic registration algorithm. Our wavelet-based registration algorithm is tested successfully with data from the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) and the Landsat Thematic Mapper (TM), which differ by translation and/or rotation. By the choice of high-frequency wavelet features, this method is similar to an edge-based correlation method, but by exploiting the multiresolution nature of a wavelet decomposition, our method achieves higher computational speeds for comparable accuracies. This algorithm has been implemented on a single-instruction multiple-data (SIMD) massively parallel computer, the MasPar MP-2, as well as on the CrayT3D, the Cray T3E, and a Beowulf cluster of Pentium workstations. View full abstract»

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  • Polarimetric mode of MIRAS

    Page(s): 1755 - 1768
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (481 KB) |  | HTML iconHTML  

    The L-band Microwave Imaging Radiometer with Aperture Synthesis (MIRAS), scheduled to be flown as single payload on board the European Soil Moisture and Ocean Salinity (SMOS) mission, has a very wide field of view and synthesizes narrow beams by means of two-dimensional (2-D) interferometry, the same concept used in radio astronomy. Wide field of view is indeed a key feature of this radiometer, which leads naturally to the measurement of the full vector of brightness temperatures of the image. This paper analyzes the theory of polarimetry in the 2-D wide-field-of-view microwave interferometry and describes the way MIRAS will measure the polarimetric brightness temperatures. View full abstract»

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  • Contextual clustering for image labeling: an application to degraded forest assessment in Landsat TM images of the Brazilian Amazon

    Page(s): 1833 - 1848
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB) |  | HTML iconHTML  

    The modified adaptive pappas clustering (MPAC) algorithm, previously published in the image processing literature, is proposed as a valuable tool in the analysis of remotely sensed images where texture information is negligible. Owing to its contextual, adaptive, and multiresolutional labeling approach, MPAC preserves genuine but small regions, is easy to use (i.e., it requires minor user interaction to run), and is robust to changes in input parameters. As an application example, an MPAC-based three-stage classifier is applied to degraded forest detection in Landsat Thematic Mapper (TM) scenes of the Brazilian Amazon, where intermediate states of forest alterations caused by anthropogenic activities can be characterized by image structures 1-3 pixels wide. In three TM images of the Para test site, where classification results are validated by means of qualitative and quantitative comparisons with aerial photos, degraded forest areas cover 13% to 45% of the image ground coverage. In the Mato Grosso test site, the degraded forest class overlaps with 1) 10% of the closed-canopy forest detected by the deforestation mapping program of the Food and Agriculture Organization (FAO, 1992), and 2) 19% of the closed-canopy forest detected by the Tropical Rain Forest Information Center (TRFIC, 1996). These figures are in line with the conclusions of a study where present estimates of annual deforestation for the Brazilian Amazon are speculated to capture less than half of the forest area that is actually impoverished each year. View full abstract»

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  • Radiative transfer solution using initial values in a scattering and absorbing atmosphere with surface reflection

    Page(s): 1889 - 1892
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    The radiative transfer equation in a planar-stratified atmosphere with multiple scattering is solved by numerically integrating an ensemble of trial functions which are constructed so as to satisfy the boundary conditions (downward-propagating radiances) at the top of the atmosphere. The boundary conditions at the surface (reflection or scattering) are imposed after integration through the atmosphere. Opaque atmospheres constitute a special case of the latter boundary condition. The algorithm is very efficient because it requires solution, only once, of a set of linear equations of rank equal to half the number of radiation streams. View full abstract»

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  • An image change detection algorithm based on Markov random field models

    Page(s): 1815 - 1823
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB) |  | HTML iconHTML  

    This paper addresses the problem of image change detection (ICD) based on Markov random field (MRF) models. MRF has long been recognized as an accurate model to describe a variety of image characteristics. Here, we use the MRF to model both noiseless images obtained from the actual scene and change images (CIs), the sites of which indicate changes between a pair of observed images. The optimum ICD algorithm under the maximum a posteriori (MAP) criterion is developed under this model. Examples are presented for illustration and performance evaluation. View full abstract»

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  • Classification of pixels in a noisy grayscale image of polar ice

    Page(s): 1879 - 1884
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB)  

    Often, in synthetic aperture radar (SAR) images of polar ice, one encounters shadow-like features across the images. Such features make it difficult to classify pixels into ice and water. Accordingly, it becomes a challenge to determine the true size and boundaries of ice floes in an SAR image of polar ice. We develop a simple statistical procedure which classifies pixels of an image by eliminating the effects of shadow-like features. Methodology developed in this paper is illustrated using some noisy SAR images of ice floes in the Arctic sea. View full abstract»

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  • A canonical problem in electromagnetic backscattering from buildings

    Page(s): 1787 - 1801
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (450 KB)  

    In this paper, a geometric and electromagnetic model of a typical element of urban structure is presented, in order to analytically evaluate in closed form its electromagnetic return to an active microwave sensor. This model can be used to understand what information on geometric and dielectric properties of a building can be extracted from microwave remote sensing data. The geometrical model consists of a rectangular parallelepiped whose vertical walls form a generic angle with respect to the sensor line of flight. The parallelepiped is placed on a rough surface. The radar return from such a structure can be decomposed into single-scattering contributions from the (rough) ground, the building roof (a plane surface in our model), and vertical walls and multiple scattering contributions from dihedral structures formed by vertical walls and ground. In our model, single-scattering contributions are evaluated by using either physical optics (PO) or geometrical optics (GO), depending on surface roughness. In order to account for multiple scattering between buildings and terrain, we use GO to evaluate the field reflected by the smooth wall toward the ground (first bounce) or the sensor (second or third bounce) and GO or PO (according to ground surface roughness) to evaluate the field scattered by the ground toward the wall (first or second bounce) or the sensor (second bounce). Finally, the above model is used to analyze the field backscattered from a building as a function of the main scene parameters; in particular, the angle between vertical walls and sensor line of night and the dependence on the look angle are analyzed. View full abstract»

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IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING (TGRS) is a monthly publication that focuses on the theory, concepts, and techniques of science and engineering as applied to sensing the land, oceans, atmosphere, and space; and the processing, interpretation, and dissemination of this information.

 

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Editor-in-Chief
Antonio J. Plaza
University of Extremadura