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Geoscience and Remote Sensing, IEEE Transactions on

Issue 4 • Date Jul 1989

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Displaying Results 1 - 15 of 15
  • The E-parallel polarization response of a two-dimensional heterogeneous layer modeled by two thin sheets

    Page(s): 369 - 374
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    The flexibility of the thin-sheet technique for modeling two-dimensional structures is extended by analyzing the response to E-parallel to the strike of the anomaly polarization, also known as the transverse electric (TE) mode, when a heterogeneous Earth is modeled by two thin sheets over a horizontally stratified half-space. The electromagnetic fields induced by the heterogeneous layer when a uniform plane wave is normally incident on the Earth are expressed as integral equations, which are then evaluated using the method of moments. The resulting matrix equations are solved by the Gauss-Seidel method, and the magnetotelluric impedance is calculated View full abstract»

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  • Consideration of vertical resolution for near nadir-looking spaceborne radar

    Page(s): 354 - 357
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    A definition of the effective vertical resolution for a down-looking rain radar is proposed on the basis of a general consideration of radar resolution in which the radar resolution for an arbitrary direction is determined by an average radar response function. Calculations of the vertical resolution are made for typical spaceborne radar parameters. The results can be applied to improving the accuracy in radar measurements View full abstract»

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  • Self-consistency aspects of dielectric mixing theories

    Page(s): 403 - 415
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    Dielectric mixing formulas that relate the effective permittivity of a heterogeneous medium with the properties of the constituent materials are considered. The restriction for this approach is that the sizes of the inclusions in the mixture have to be considerably smaller than the wavelength to avoid scattering effects. The mixing rules are presented for cases where the scatterers can be homogeneous or multilayer spheres. The formula contains a free parameter v, and for different choices of this parameter, many mixing formulae result as special cases of the given mixing rule. Mixing formulas presented in the literature are also reviewed and the results from different formulae are compared, using dry and wet snow as paradigmatic examples View full abstract»

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  • Block adaptive quantization of Magellan SAR data

    Page(s): 375 - 383
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1076 KB)  

    A report is presented on a data compression scheme that will be used to reduce the SAR (synthetic-aperture radar) data rate on the US NASA Magellan (MGN) mission to Venus. The MGN spacecraft has only one scientific instrument, namely, a radar system that is used for imaging the surface. for altimetric profiling of the planet topography, and for measuring radiation of the planet surface. A straightforward implementation of the scientific requirements of the mission results in a data rate higher that can be accommodated by the available system bandwidth. A data-rate-reduction scheme which includes operation of the radar in burst mode and block adaptive quantization of the SAR data is selected to satisfy the scientific requirements View full abstract»

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  • Wavelet parameter and phase estimation using cumulant slices

    Page(s): 452 - 455
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    A simple, closed-form expression relates one-dimensional output cumulant statistics with the parameters of a known-order moving-average wavelet. Based on this relationship the author obtains unique parameter and phase estimates of autoregressive moving-average seismic wavelets. The input reflectivity sequence is assumed to be non-Gaussian, independent, and identically distributed. The wavelet is not assumed to be minimum phase and is allowed to include all-pass factors. The seismogram is contaminated by additive-colored Gaussian noise. Simulations demonstrate that the algorithm works well for moderate-size data records with a relatively low signal-to-noise ratio View full abstract»

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  • A general solution of the electrode resistance problem

    Page(s): 455 - 459
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    Starting from the stationary current field problem of a three-axial ellipsoid, the solution of the electric potential is known. This solution and the results of earlier papers are used to calculate the electrode resistances. The main advantage of this method is that it contains the calculation steps not only for electrodes developed by three-axial ellipsoids but also for other electrode forms; e.g. spheres, rotational ellipsoids, etc View full abstract»

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  • The RADTRAN microwave surface emission models

    Page(s): 433 - 440
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    The AFGL RADTRAN microwave atmospheric transmission/brightness temperature computer code has been enhanced by a surface emissivity modeling subpackage. This enhancement will provide realistic calculations of frequency-dependent polarized surface emissivity to support simulations of Earth-viewing microwave sensing systems. These models are appropriate for the frequency range 1-40 GHz. Two distinct modeling approaches have been applied: one based on wave theory for random discrete scatterers, and one based on radiative transfer theory for continuous random media. The former approach is used to model the ocean surface, various forms of sea ice, and snow over land, whereas the latter is used to treat soils and vegetation. Surface emissivity values obtained from these models as functions of polarization, frequency, and look angle are illustrated View full abstract»

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  • A statistical approach for determining radiometric precisions and accuracies in the calibration of synthetic aperture radar imagery

    Page(s): 416 - 427
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1044 KB)  

    A model that estimates a relative error bound for the radiometric calibration of synthetic aperture radar (SAR) imagery is presented. This model is based on a statistical `Coefficient of Variation of Error Model', which produces a relative error bound by propagating the measured or estimated uncertainties in the radar system parameters utilized to correct digitally processed SAR image intensity values. Using this model, algorithms are generated for absolute and relative radiometric calibration of SAR imagery. These algorithms are parametrically exercised using radar system parameters from an existing airborne SAR system to determine their impact on the relative error bound View full abstract»

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  • A scale model for studying ground penetrating radars

    Page(s): 358 - 363
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    A scale model developed for experimentally studying ground penetrating radars is described. The model is one-third full size and is used with transient signals that have significant frequency content within the range 150 MHz to 1.5 GHz. A unique feature is that the soil in the model is represented by an emulsion, which is mixture of mineral oil, saline solution, and a stabilizing agent. This emulsion is a scale model for red clay soil; it matches the electrical parameters of the clay, including the dispersion in the conductivity, over a ten-to-one frequency range. Typical results measured with the model are discussed. These include the measurement of the electric field transmitted by the radar into the soil and the measurement of radar signatures for pipes of various composition buried in the ground View full abstract»

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  • Near-field detection of buried dielectric objects

    Page(s): 364 - 368
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    The plane-wave scattering-matrix method is used to compute the response of a detector to a buried dielectric scatterer. The Born approximation is used to derive the scattering matrix for scatterers of small dielectric contrast, but the general theory is not limited to such cases. Specific numerical results are generated for a UHF dipole detector swept over a buried dielectric cube. The maximum response is obtained when the detector is located at the soil interface, and the response decays rapidly with the detector height. The sweep curves are symmetrical in the horizontal direction and have a null when the detector is directly over the object. An experimental curve for a free-space environment has the same qualitative features View full abstract»

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  • The structure of red-infrared scattergrams of semivegetated landscapes

    Page(s): 441 - 451
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    A physically based linear stochastic geometric canopy-soil reflectance model is presented for characterizing spatial variability of semivegetated landscapers at subpixel and regional scales. Landscapes are conceptualized as stochastic geometric surfaces, incorporating not only the variability in geometric elements but also the variability in vegetation and soil background reflectance, which can be important in some scenes. The model is used to investigate several possible mechanisms which contribute to the often observed characteristic triangular shape of red-infrared scattergrams of semivegetated landscapes. Scattergrams of simulated semivegetated scenes are analyzed with respect to the scales of the satellite pixel and subpixel components View full abstract»

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  • Ground network optimization using satellite information: application to the French heliographic network

    Page(s): 459 - 462
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    The authors deal with the setting up of sunshine recording stations using satellite information. Most statistical criteria used to select measurement locations rely on knowledge of the correlation structure of the measured phenomenon. As this structure is generally not known extensively, it must be modeled under homogeneity assumptions. An alternative solution is proposed to avoid such modeling by using instead the correlation structure deduced from remote-sensed measurements of the studied phenomenon. A case study is presented View full abstract»

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  • Recursive deconvolution of Bernoulli-Gaussian processes using a MA representation

    Page(s): 384 - 394
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    The authors deal with the problem of deconvolution of Bernoulli-Gaussian random processes observed through linear systems. This corresponds to situations frequently encountered in areas such as geophysics, ultrasonic imaging, and nondestructive evaluation. Deconvolution of such signals is a detection-estimation problem that does not allow purely linear data processing, and the nature of the difficulties greatly depends on the type of representation chosen for the linear system. A MA degenerate state-space representation is used. It presents interesting algorithmic properties and simplifies implementation problems. To obtain a globally recursive procedure, a detection step is inserted in an estimation loop by Kalman filtering. Two recursive detectors based on maximum a posteriori and maximum-likelihood criteria, respectively, are derived and compared View full abstract»

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  • Transient electromagnetic response of a permeable and conducting ground to a linear current ramp switch-off

    Page(s): 428 - 432
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    The asymptotic representation for late times of the transient electric field above and on a uniform permeable and conducting ground is derived with the hitherto untreated effects of a ramp switch-off source current. The source is a vertically oriented finite loop placed on the ground. Certain response functions are defined and the results are compared directly to those of a Heaviside switch-off. The authors show that the ramp-time dependence is given by certain well-defined functions multiplying the respective terms of the series for the field produced by a Heaviside switch-off source. They also show that for late times t , the first term shows an enhancement of the ramp switch-off field relative to the Heaviside of the order of 1+5t0/4t, where t0 is the ramp time View full abstract»

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  • Polarization utilization in the microwave inversion of leaf angle distributions

    Page(s): 395 - 402
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (692 KB)  

    The inverse problem of deducting the inclination angle distribution of leafy vegetation has been investigated using L-band multipolarization backscattered data. The modeling procedure replaces canopy leaves with thin circular dielectric disks. The Born approximation is then used to establish a linear relationship between the radar backscattering coefficients and the leaf inclination angle distribution. The inversion of the leaf angle distribution is carried out for horizontal, vertical, and cross-polarized data. It is shown that the results of the inversion using vertical and cross-polarized data are comparable to the inversion results of horizontally polarized data obtained previously (R. Lang and H. Saleh, 1985) 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