By Topic

Geoscience and Remote Sensing, IEEE Transactions on

Issue 3 • Date May 1998

Filter Results

Displaying Results 1 - 25 of 35
  • Raindrop axis ratios and size distributions in Florida rainshafts: an assessment of multiparameter radar algorithms

    Page(s): 703 - 715
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    Eleven penetrations of rainshafts by the University of Wyoming King Air (WKA) aircraft equipped with a two-dimensional (2D) optical array probe are studied in coordination with multiparameter radar measurements from the National Center for Atmospheric Research (NCAR) CP-2 radar collected in a multicellular storm that occurred on August 8, 1991, of the Convective and Precipitation/Electrification (CaPE) experiment. A comparison is made between the mass-weighted mean diameter (Dm) and rainrate (R) computed from the nine-size spectra and their estimates from multiparameter radar algorithms based on Zdr , and Zh. It was found that Dm could be estimated with a mean bias of 0.07 mm and a standard deviation of 0.35 mm. Rainrates (in the range of 10-60 mmh-1) could be estimated from Zh, and Zdr with a mean bias of 1-4% and fractional standard error (FSE) of 30-40% depending on the estimator used. Raindrop axis ratios are analyzed as a function of volume equivalent spherical diameter (Deq) in the range 2-6 mm. The mean axis ratio versus the Deq relationship was found to be consistent with previous data from the High Plains (from Colorado and Montana). A study of fluctuations of axis ratio (about their mean value) showed that most drops have axis ratios close to their mean values with oscillation amplitudes to be typically ±10% in axis ratio, again consistent with the earlier High Plains results View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The integral equation model and surface roughness signatures in soil moisture and tillage type determination

    Page(s): 833 - 837
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (100 KB)  

    A proposed application of RADARSAT, C-band, HH-polarized, satellite-based, synthetic aperture radar (SAR) identifies agricultural tillages and soil moisture through multi-incidence angle observations. A procedure to accomplish this has been developed using the integral equation (IE) model and a roughness signature for each anticipated tillage type. Through a comparison of the IE model, using each roughness signature over a range of moisture levels, to the measured backscatter one can select the case with the least error. This procedure yields little confusion between rough and smooth tillages using scatterometer measurements of test plots where extensive moisture and roughness ground truth were obtained. There is, however, significant confusion in classification of tillages with similar roughness characteristics. The bare-field moisture level was determined with a mean error of 1.8% and a standard deviation of 5.8%, when the initial moisture level was constrained to ±10% of the actual level View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Application of successive approximation method to the computation of the Green's function in axisymmetric inhomogeneous media

    Page(s): 732 - 737
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    The successive approximation method (SAM) is applied to the computation of the Green's function in axisymmetric inhomogeneous media, SAM is implemented by using an iterative procedure that produces a series, and the series is proven to be a Taylor series. The condition of the convergence is derived from the theory of functions of several complex variables. In each iteration, the Fourier-Hankel transform and its inverse are applied to the approximation of some order of the Green's function and the result is the approximation one order higher than the original. Fast Fourier-Hankel transform (FFHT) is employed to speed up the computation, and thereby, an algorithm SAM-FFHT is formulated View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Further results on relationship between spectral unmixing and subspace projection

    Page(s): 1030 - 1032
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (60 KB)  

    A recent short communication, J. J. Settle (1996), showed that an orthogonal subspace projection (OSP) classifier developed for hyperspectral image classification in J. Harsanyi et al. (1994) was equivalent to a maximum likelihood estimator (MLE) resulting from a standard method of linear unmixing. It further concluded that the MLE subsumed the OSP classifier in spite of a constant difference in their magnitudes. Coincidentally, the equivalence of the OSP approach to linear unmixing was also derived in J. Harsanyi (1993) and T. M. Tu et al. (1997) by using the least-squares estimation with the same abundance estimate given by the MLE. In this communication, the author shows, on the contrary, that the MLE can be viewed as an a posteriori version of the OSP classifier and, thus, belongs to a family of OSP-based classifiers. More importantly, the author further shows that the constant produced by the MLE determines abundance estimation and has nothing to do with classification. As a result, it only alters the abundance concentration of the classified pixels, but not classification results View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimal seismic deconvolution: distributed algorithms

    Page(s): 779 - 792
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    Deconvolution is one of the most important aspects of seismic signal processing. The objective of the deconvolution procedure is to remove the obscuring effect of the wavelet's replica making up the seismic trace and therefore obtain an estimate of the reflection coefficient sequence. This paper introduces a new deconvolution algorithm. Optimal distributed estimators and smoothers are utilized in the proposed solution. The new distributed methodology, perfectly suitable for a multisensor environment, such as the seismic signal processing, is compared to the centralized approach, with respect to computational complexity and architectural efficiency. It is shown that the distributed approach greatly outperforms the currently used centralized methodology offering flexibility in the design of the data fusion network View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multichannel trace interpolation in the presence of spatial aliasing

    Page(s): 1025 - 1030
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    Steep seismic events are often aliased due to spatial undersampling of wave fields creating different kinds of coherent noises and corrupting the migration process, O. Yilmaz (1987). To avoid the expensive costs of high-resolution spatial sampling, seismic traces are interpolated. A novel spatial interpolation algorithm, based on a narrowband multichannel model, is considered View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Permutations and prediction for lossless compression of multispectral TM images

    Page(s): 999 - 1003
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB)  

    This paper introduces a reversible remapping technique based on sorting permutations. The algorithm developed utilizes a remapping technique and employs linear predictive operators on a pair of band for TM images. It is shown that the algorithm produces substantial improvements in the compression ratio as compared to the results reported previously View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Classification accuracy improvement of neural network classifiers by using unlabeled data

    Page(s): 1020 - 1025
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB)  

    Classification accuracy improvement of neural network classifiers using unlabeled testing data is presented. In order to increase the classification accuracy without increasing the number of training data, the network makes use of testing data along with training data for learning. It is shown that including the unlabled samples from underrepresented classes in the training set improves the classification accuracy of some of the classes during supervised-unsupervised learning View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Synthetic aperture radiometry evaluated by a two-channel demonstration model

    Page(s): 822 - 832
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    The Technical University of Denmark (TUD) Synthetic Aperture Radiometer (SARad) is a two-channel demonstration model that can simulate a two-dimensional (2D) thinned array radiometer having an unfilled aperture populated with several small antenna elements. Aperture synthesis obtained by interferometric measurements using the antenna elements in pairs, followed by an image reconstruction based on an inverse Fourier transform, results in an imaging instrument without the need of mechanical scan. The thinned aperture and the nonscanning feature make the technique attractive for spaceborne radiometer systems, especially at low frequencies. The TUD SARad demonstration model consists of a two-channel Ku-band correlation radiometer with two horn antennas and an antenna mounting structure enabling the horns to be mounted in relevant positions within a certain aperture. A total aperture synthesis is obtained by sequentially placing the two antenna elements in all required pairs of positions and measuring the corresponding samples of the visibility function. The system has been used to demonstrate 2D synthetic aperture imaging of complex targets in outdoor ground experiments, a special feature of the system is that it uses a focused antenna system, thus enabling a short distance to the target. Set still utilizing image reconstruction algorithms identical to those used in a normal far-field situation. The aperture synthesis theory is discussed, with special emphasis on focused systems; the radiometer system is described; and images suitable for demonstration of resolution and other imaging properties are presented and discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Bayesian classification and class area estimation of satellite images using stratification

    Page(s): 803 - 812
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    The paper describes an iterative extension to maximum a posteriori (MAP) supervised classification methods. A posteriori probabilities per class are used for classification as well as to obtain class area estimates. From these, an updated set of prior probabilities is calculated and used in the next iteration. The process converges to statistically correct area estimates. The iterative process can be combined effectively with a stratification of the image, which is made on the basis of additional map data. Moreover, it relies on the sample sets being representative. Therefore, the method is shown to be well applicable in combination with an existing GIS. The paper gives a description of the procedure and provides a mathematical foundation. An example is presented to distinguish residential, industrial, and greenhouse classes. A significant improvement of the classification was obtained View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A novel across-track SAR interferometry simulator

    Page(s): 950 - 962
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    A novel across-track interferometric synthetic aperture radar (SAR) raw signal simulator is presented. It is based on an electromagnetic backscattering model of the scene and an accurate description of the SAR system impulse response function. A set of meaningful examples are also presented. They show that the proposed simulator is structurally consistent and correctly simulates the decorrelation effect, both in the mean and in the distribution sense View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Application of ERS-1 wind scatterometer data to soil frost and soil moisture monitoring in boreal forest zone

    Page(s): 849 - 863
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    The feasibility of the ERS-1 Wind Scatterometer (WS) for monitoring the boreal forest zone is investigated, concentrating on soil frost and soil moisture monitoring. The ERS-1 WS measures the target area with coarse spatial resolution (about 50 km) using three separate antenna beams and a wide angular range. The investigations are concerned with the boreal forest zone using data (1) from test areas located in Finland and (2) covering the whole northern European boreal forest zone. The seasonal behavior of WS data is studied and a semiempirical forest backscattering model-based inversion method for the retrieval of soil moisture and for soil frost monitoring from WS data is developed. The developed inversion method employs nearly simultaneous three-beam measurements and a varying incidence angle. Promising results were obtained in the monitoring of soil frost, and the retrieval of soil moisture also appears to be a feasible field of application. The applicability of the instrument for forest biomass retrieval using single images was found to be limited to long-term change detection View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electromagnetic properties of dry and water saturated basalt rock, 1-110 GHz

    Page(s): 754 - 766
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    This paper reports on the measured electromagnetic properties of dry and water saturated basalt rock over a frequency range of 1-110 GHz. Tests were conducted in standard waveguides below 12 GHz and with free-space systems above 12 GHz. The basalt used in this investigation was found to be nonmagnetic. Measured relative permittivities for the dry basalt varied from approximately (8.19,-0.71) at 1.12 GHz to (6.80,-0.49) at 110 GHz. The porosity of the basalt was determined to be roughly 10%. Properties of water saturated basalt were also measured at several frequencies and compared to theoretical predictions based on a simple Maxwell-Garnett mixing theory. Finally, the potential of using microwave tomography on basalt rock was examined based on the resulting properties View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Laboratory measurements of radar depolarization signatures in microwave pulse transmission through randomly distributed spherical scatterers

    Page(s): 1011 - 1015
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (124 KB)  

    Laboratory measurements of a backscattered signal for large spherical scatterers are performed to investigate the range of applicability of approximate theory, which the authors used in interpreting the measured depolarization signatures of rain. The measured linear depolarization ratios (LDRs) are in remarkably good agreement with theoretical calculations View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A novel phase unwrapping method based on network programming

    Page(s): 813 - 821
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    Phase unwrapping is the reconstruction of a function on a grid given its values mod 2π. Phase unwrapping is a key problem in all quantitative applications of synthetic aperture radar (SAR) interferometry, but also in other fields. A new phase unwrapping method, which is a different approach from existing techniques, is described and tested. The method starts from the fact that the phase differences of neighboring pixels can be estimated with a potential error that is an integer multiple of 2π. This suggests the formulation of the phase unwrapping problem as a global minimization problem with integer variables. Recognizing the network structure underlying the problem makes for an efficient solution. In fact, it is possible to equate the phase unwrapping problem to the problem of finding the minimum cost flow on a network, for the solution of which there exist very efficient techniques. The tests performed on real and simulated interferometric SAR data confirm the validity of the approach View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Validation of alpine glacier velocity measurements using ERS Tandem-Mission SAR data

    Page(s): 974 - 984
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    Five ascending and four descending ERS-1/2 tandem-mode synthetic aperture radar (SAR) interferometry (InSAR) data pairs with useful scene coherence are used to measure the surface flow field of an alpine glacier in the Canadian Rocky Mountains. The topographic component of the interferogram phase is calculated by using a digital elevation model (DEM) of the terrain and precise orbit data to reconstruct the ERS InSAR imaging geometry. The DEM is derived from the Canada Centre for Remote Sensing (CCRS) Convair-580 airborne SAR interferometer. As dual line-of-sight (LOS) measurements are not sufficient to completely resolve the three-dimensional (3D) surface flow field, several different assumptions for determining the missing variables are considered, and the 3D surface flow field is estimated by using single and dual LOS measurements. The InSAR results agree with historic and coincident displacement measurements made using traditional point surveying techniques View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A combined steepest descent-fast multipole algorithm for the fast analysis of three-dimensional scattering by rough surfaces

    Page(s): 738 - 748
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    A new technique, the steepest descent-fast multipole method (SDFMM), is developed to efficiently analyze scattering from perfectly conducting random rough surfaces. Unlike other prevailing methods, this algorithm has linear computational complexity and memory requirements, making it a suitable candidate for analyzing scattering from large rough surfaces as well as for carrying out Monte Carlo simulations. The method exploits the quasiplanar nature of rough surfaces to efficiently evaluate the dyadic Green's function for multiple source and observation points. This is achieved through a combination of a Sommerfeld steepest descent integral and a multilevel fast multipole-like algorithm based on inhomogeneous plane wave expansions. The fast evaluation of the dyadic Green's function dramatically speeds up the iterative solution of the integral equation for rough surface scattering. Several numerical examples are presented to demonstrate the efficacy and accuracy of the method in analyzing scattering from extremely large finite rough surfaces View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Automatic extraction of drainage network from digital terrain elevation data: a local network approach

    Page(s): 1007 - 1011
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    A local network for the automatic extraction of drainage networks from elevation data is described. The methodology demonstrates how a large number of locally connected processing units can solve the global problem of drainage network extraction. The methodology has advantages over previous methods and is able to extract lakes as well as streams and rivers View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The multilook polarimetric whitening filter (MPWF) for intensity speckle reduction in polarimetric SAR images

    Page(s): 1016 - 1020
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB)  

    The polarimetric whitening filter (PWF) proposed by Novak et al. is extended to the multilook case to form a multilook PWF (MPWF) fur intensity speckle reduction in multilook polarimetric synthetic aperture radar (SAR) images. The MPWF optimally processes the multilook covariance matrix to generate a minimum-speckle intensity image. The amount of speckle reduction achievable by using the MPWF is quantified. The authors also show that the MPWF is equivalent to a maximum likelihood (ML) filter. Experimental results with the NAS/Jet propulsion laboratory (JPL) airborne L-band, four-look polarimetric SAR data demonstrate the effectiveness of the MPWF View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Validity of ERS-1 altimeter corrections

    Page(s): 1003 - 1006
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (64 KB)  

    Sea surface height (SSH) observations from satellite altimeter are subjected to various types of environmental and geophysical errors. To get the small amplitude (of the order of a few centimeters) dynamic oceanographic signals from altimeters, effects due to these errors have to be corrected. The validity of each of the correction terms to the ERS-1 altimeter measurements have been studied. Most of the corrections reduced the variance and have thus been found to be effective altimetric corrections View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A three-component scattering model for polarimetric SAR data

    Page(s): 963 - 973
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    An approach has been developed that involves the fit of a combination of three simple scattering mechanisms to polarimetric SAR observations. The mechanisms are canopy scatter from a cloud of randomly oriented dipoles, evenor double-bounce scatter from a pair of orthogonal surfaces with different dielectric constants and Bragg scatter from a moderately rough surface. This composite scattering model is used to describe the polarimetric backscatter from naturally occurring scatterers. The model is shown to describe the behavior of polarimetric backscatter from tropical rain forests quite well by applying it to data from NASA/Jet Propulsion Laboratory's (JPLs) airborne polarimetric synthetic aperture radar (AIRSAR) system. The model fit allows clear discrimination between flooded and nonflooded forest and between forested and deforested areas, for example. The model is also shown to be usable as a predictive tool to estimate the effects of forest inundation and disturbance on the fully polarimetric radar signature. An advantage of this model fit approach is that the scattering contributions from the three basic scattering mechanisms can be estimated for clusters of pixels in polarimetric SAR images. Furthermore, it is shown that the contributions of the three scattering mechanisms to the HH, HV, and VV backscatter can be calculated from the model fit. Finally, this model fit approach is justified as a simplification of more complicated scattering models, which require many inputs to solve the forward scattering problem View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A new decomposition of radar polarization signatures

    Page(s): 933 - 939
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    A method for the decomposition of radar polarization signatures is developed. The polarization backscattering model is assumed to consist of odd, double, Bragg, and cross backscattering components, and the Mueller matrix is the sum of the Mueller matrices of these four scattering mechanisms. The technique of least squares (LS) is then used to find the best combination of these four components. Using NASA/Jet Propulsion Laboratory (JPL) AirSAR data, the results of the decomposition agree with the general understanding of radar backscatter. In most cases, the accuracy of the decomposition is more than 95% for linear polarizations and more than 85% for any other polarizations View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Velocity vectors for features of sequential oceanographic images

    Page(s): 985 - 998
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    This paper investigates a fundamental problem of determining the position, orientation, and velocity field of the Gulf Stream in time-varying imagery. The authors propose an approximation method to characterize the deformation of these image motions for the purpose of estimating the velocity field of these images. The technique is focused on the interpretation of the change in the extracted features of the Gulf Stream. The underlying technique employs a triangulation of the region by a simplicial approximation of the velocity field on each triangle. A generalized computational framework, an outline of the mathematical foundation, and an implementation are presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Radar measurements of snow: experiment and analysis

    Page(s): 864 - 879
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    This paper considers two specific types of experiments conducted to improve the authors' understanding of radar backscatter from snow-covered ground surfaces. The first experiment involves radar backscatter measurements at Cand X-band of artificial snow of varying depths. The relatively simple target characteristics, combined with an exhaustive ground truth effort, make the results of this experiment especially amenable to comparison with predictions based on theoretical methods for modeling volume-scattering media. It is shown that both conventional and dense-medium radiative transfer models fail to adequately explain the observed results. A direct polarimetric inversion approach is described by which the characteristics of the snow medium are extracted from the measured data. The second type of experiment examined in this study involves diurnal backscatter measurements that were made contemporaneously with detailed measurements of the snow-wetness depth profiles of the observed scene. These data are used to evaluate the capability of a recently proposed algorithm for snow wetness retrieval from polarimetric synthetic aperture radar (SAR) measurements, which has hithertofore been applied only to data from very complex and extended mountainous terrains View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Hybrid Born iterative method in low-frequency inverse scattering problem

    Page(s): 749 - 753
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (148 KB)  

    With its fast convergence, the distorted Born iterative method (DBIM) has been widely used in low-frequencg inverse scattering analysis, however its inherent drawback, sensitive-to-noise disturbance, may greatly limit its practical applications. In this paper, the numerical analysis is made to compare the DBIM and the Born iterative method (BIM). Then a hybrid BIM is presented. In this method, the DBIM is employed to speed the solution convergence in the initial several iterations and the BIM is used to improve the solution stability in the later iterations. The switch condition is also given. The simulation results show that the method is valid for the inverse scattering solution View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

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