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Geoscience and Remote Sensing, IEEE Transactions on

Issue 2 • Date Mar 1990

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Displaying Results 1 - 15 of 15
  • Limitations in recursive wavefield continuation with spatial wavelets [seismic reflection modeling]

    Publication Year: 1990 , Page(s): 272 - 274
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    Some problem that have to be avoided in wavefield continuation in the space-frequency domain are instability, inaccuracy, and poor steep-dip performance. The practical design in convolutional operators for one-way wavefield continuation in the space-frequency domain places constraints on the operator length and range of useful wavenumbers. These problems are inherent in the design of anti-aliased, finite-length continuation operators and their subsequent application in a recursive manner. The author discusses two major limiting factors anti-aliasing and aperture limiting View full abstract»

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  • A multiple scattering solution for the effective permittivity of a sphere mixture

    Publication Year: 1990 , Page(s): 207 - 214
    Cited by:  Papers (17)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    A recursive algorithm for calculating the exact solution of a random assortment of spheres is described. In this algorithm, the scattering from a single sphere is expressed in a one-sphere T matrix. The scattering from two spheres is expressed in terms of two-sphere T matrices, which are related to the one-sphere T matrix. A recursive algorithm to deduce the (n+1)-sphere T matrix from the n-sphere T matrix is derived. With this recursive algorithm, the multiple scattering from a random assortment of N spheres can be obtained. This results in an N2 algorithm rather than the normal N3 algorithm. As an example, the algorithm is used to calculate the low-frequency effective permittivity of a random assortment of 18 dielectric spheres. The effective permittivity deviates from the Maxwell-Garnett result for high contrast and high packing fraction. With a high packing fraction, dielectric enhancement at low frequency is possible View full abstract»

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  • The unpolarized component in polarimetric radar observations of forested areas

    Publication Year: 1990 , Page(s): 268 - 271
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    A polarimetric radar measures the complete scattering matrix of a target. For a forest and other natural targets, the average return is, in general, partially polarized. Conditions on the second-order statistics of the scattering matrix under which the return is fully polarized are derived, and it is shown that these conditions are connected with the eigenvalues of the covariance matrix. The result of this analysis is a set of three quantities which indicate the ability of a scatterer to generate an unpolarized component. These quantities for forested areas are shown View full abstract»

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  • SAR image statistics related to atmospheric drag over sea ice

    Publication Year: 1990 , Page(s): 158 - 165
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1048 KB)  

    The possibility of using synthetic aperture radar (SAR) data to distinguish sea-ice regions with different atmospheric drag is explored. Both the amplitude of the radar return and statistics derived from SAR image data are examined. Roughness statistics data from several pack-ice areas are used in a backscatter model to predict the return from surfaces with measured drag coefficients. The results suggest that the scattering coefficient for typical radar wavelengths is insensitive to the roughness elements responsible for the observed drag coefficient variations over pack ice free of major ridges. For marginal ice zones, where ice concentration and floe deformation contribute to atmospheric drag, a simple model for the atmospheric boundary layer is used to provide qualitative relationships between drag coefficient and regional ice properties (ice concentration, floe size distribution, floe edge density) derivable from SAR data. Simple algorithms to produce maps of ice concentration and edge density are outlined and applied to 23.5-cm SAR digital image data View full abstract»

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  • Phase calibration of imaging radar polarimeter Stokes matrices

    Publication Year: 1990 , Page(s): 246 - 252
    Cited by:  Papers (45)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (756 KB)  

    It is shown that the Stokes matrices measured by an imaging radar polarimeter provide enough information for the accurate phase calibration of the observed polarimetric characteristics of a surface. This is important because it allows the data to be reduced in volume in an operational synthetic aperture radar correlator with no prior knowledge of the conditions at the surface, and the end user can later select the particular region where he or she is comfortable with making an assumption regarding the relative phases of the hh and νν signals. No ground calibration equipment is necessary, as all important parameters are derived from the data themselves View full abstract»

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  • Locating and identifying compact ferrous objects

    Publication Year: 1990 , Page(s): 182 - 193
    Cited by:  Papers (8)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1200 KB)  

    A solution to the problem of magnetostatic location and identification of compact ferrous objects of arbitrary shape is presented. It is shown that, in practice, the inversion of the magnetostatic dipole field or field gradient is a necessary first step toward determining object location and identity. Several iterative and noniterative methods of determinating the dipole moment and location from field or gradient measurements are described and compared. It is shown that, given the dipole-moment estimates, it is possible to determine the identity of the dipole source in practical situations by pattern recognition. A unique prototype total field magnetometer which is capable of explicitly and accurately locating and identifying axially symmetric compact ferrous objects is described. It has performed well in preliminary tests using spheres and spheroids View full abstract»

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  • A numerical study of the separation wavenumber in the two-scale scattering approximation [ocean surface radar backscatter]

    Publication Year: 1990 , Page(s): 271 - 272
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    The modeling of radar backscatter from the ocean uses the two-scale scattering approximation. This approximation assumes that the continuous spectrum of the ocean can be separated at some wavenumber into large- and small-scale surfaces, allowing use of physical optics and small perturbation methods. The authors investigate the choice of the separation wavenumber by comparing two-scale calculations and exact numerical calculations for a randomly rough surface with a power law spectrum View full abstract»

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  • A phase reconstruction algorithm from bispectrum [seismic reflection data]

    Publication Year: 1990 , Page(s): 166 - 170
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    A computationally efficient procedure for the reconstruction of the impulse response of a (minimum- or nonminimum-phase) linear time-invariant system from its bispectrum is presented. This method is based on computing cepstrum of the impulse response sequence from the ω12 slice of the bispectrum. The algorithm can be implemented by using only the one-dimensional fast Fourier transform algorithm View full abstract»

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  • Estimation of subpixel vegetation cover using red-infrared scattergrams

    Publication Year: 1990 , Page(s): 253 - 267
    Cited by:  Papers (7)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1196 KB)  

    The bulk properties of discontinuous vegetation canopies are estimated at subpixel scales by applying the method of moments to a linear stochastic geometric model of canopy-soil reflectance and one set of multispectral observations without ground truth. The procedure involves the formulation of conditional moments for subsets of pixels that possess similar properties and can be identified through their common orientation in red-infrared scattergrams. The analysis is facilitated by assuming geometric similarity among the canopy elements and by formulating a sampling scale ratio in terms of the bulk geometric scales of the canopy and the pixel. Three versions of the method are demonstrated using two simulated scenes and an actual forested watershed for which aerial radiometric data and corresponding ground truth were obtained View full abstract»

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  • Laboratory evaluation of a field-portable dielectric/soil-moisture probe

    Publication Year: 1990 , Page(s): 241 - 245
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    An evaluation of an L-band dielectric soil-moisture probe conducted to examine its capabilities, calibration, and performance under laboratory conditions is discussed. Results indicated that the probe can estimate the real part of the dielectric constant over a wide range of values. The imaginary part of the dielectric constant was overestimated. Since the soil moisture estimate is made using only the real part of the dielectric constant, the probe should produce reliable estimates of soil moisture. Studies utilizing a variety of soils, ranging from a loamy sand to a clay loam, produced results which were not as variable as those predicted by the dielectric models View full abstract»

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  • Autoregressive segmentation of signal traces with applications to geological dipmeter measurements

    Publication Year: 1990 , Page(s): 171 - 181
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (896 KB)  

    A general method and algorithm for segmenting data traces according to changes in the shape and scale of their autoregressive frequency structure are discussed. The algorithm is based on the least-squares principle, which is utilized in several iterations and on several levels. In the underlying model, the transitions from one segment to another take place according to a Markov mechanism, but the algorithm works for any signal trace where the segmentwise characteristics occur in a repetitive manner. The method is illustrated on four-track geological dipmeter measurements from an unidentified oil-well drilling hole in the North Sea. How more precise boundaries between geological layers can be determined by using the algorithm is indicated. Extensive testing of the algorithm on simulated data is discussed View full abstract»

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  • A heuristic algorithm for the bistatic radar cross section for random rough surface scattering

    Publication Year: 1990 , Page(s): 202 - 206
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    Examines a heuristic algorithm which guarantees reciprocity in the cross-section equations when the phase perturbation approximation is used. The results obtained using a Gaussian surface roughness spectrum are superior to those of either the phase perturbation or the reversed phase perturbation method and agree well with the exact results obtained using a Monte Carlo integral equation technique View full abstract»

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  • Hybrid simulation of strong scattering from inhomogeneous dielectrics

    Publication Year: 1990 , Page(s): 215 - 223
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    The interaction of electromagnetic radiation with two-dimensional inhomogeneous dielectrics is described using a hybrid approach that has both analytical and computational elements. It is then applied to the simulation of microwave radar images. The scattered field is calculated in a composite fashion by considering separately the effects due to slant range projection and the physical interaction. By using a facet model, the simulated scattered field is related to the object structure. The statistics of the image are investigated as functions of the number of facets per resolution cell of the radar and the surface roughness, for smooth and rough surfaces and correlated and uncorrelated surfaces. The systematic behavior of the scattered intensity as a function of the target structure and composition is also discussed View full abstract»

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  • Polarimetric SAR calibration experiment using active radar calibrators

    Publication Year: 1990 , Page(s): 224 - 240
    Cited by:  Papers (47)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1884 KB)  

    Active radar calibrators are used to derive both the amplitude and phase characteristics of a multichannel polarimetric synthetic aperture radar (SAR) from the complex image data. Results are presented from an experiment carried out using the NASA/JPL DC-8 aircraft SAR over a calibration site at Goldstone, California. As part of the experiment, polarimetric active radar calibrators (PARCs) with adjustable polarization signatures were deployed. Experimental results demonstrate that the PARCs can be used to calibrate polarimetric SAR images successfully. Restrictions on the application of the PARC calibration procedure are discussed View full abstract»

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  • Fuzzy supervised classification of remote sensing images

    Publication Year: 1990 , Page(s): 194 - 201
    Cited by:  Papers (87)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1096 KB)  

    A fuzzy supervised classification method in which geographical information is represented as fuzzy sets is described. The algorithm consists of two major steps: the estimate of fuzzy parameters from fuzzy training data, and a fuzzy partition of spectral space. Partial membership of pixels allows component cover classes of mixed pixels to be identified and more accurate statistical parameters to be generated, resulting in a higher classification accuracy. Results of classifying a Landsat MSS image are presented, and their accuracy is analyzed View full abstract»

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Aims & Scope

 

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.

 

Full Aims & Scope

Meet Our Editors

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