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Geoscience and Remote Sensing, IEEE Transactions on

Issue 1 • Date Jan. 2002

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Displaying Results 1 - 25 of 25
  • Correction to "The effect of classifier agreement on the accuracy of the combined classifier in decision level fusion"

    Publication Year: 2002 , Page(s): 228
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  • Correction to "A joint multicontext and multiscale approach to bayesian image segmentation"

    Publication Year: 2002 , Page(s): 229
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  • Evaluation of a compound probability model with tower-mounted scatterometer data

    Publication Year: 2002 , Page(s): 42 - 49
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (238 KB) |  | HTML iconHTML  

    Six months of data from the YSCAT94 experiment conducted at the CCIW WAVES research platform on Lake Ontario, Canada, are analyzed to evaluate a compound probability model. YSCAT was an ultrawideband small footprint (≈1 m) microwave scatterometer that operated at frequencies of 2-18 GHz, incidence angles from 0° to 60°, both h-pol and v-pol, and which tracked the wind using simultaneous weather measurements. The probability distribution function of the measured instantaneous backscattered amplitude (p(a)) is compared to theoretical distributions developed from-the composite model and a simple wave spectrum. Model parameters of the resulting Rayleigh/generalized lognormal distribution probability density function (pdf) (C, a1 , and a2) are derived directly from the data and are found to demonstrate relationships with wind speed, incidence angle, and radar frequency View full abstract»

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  • Wind speed measurement using forward scattered GPS signals

    Publication Year: 2002 , Page(s): 50 - 65
    Cited by:  Papers (96)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (271 KB) |  | HTML iconHTML  

    Instrumentation and retrieval algorithms are described which use the forward scattered range-coded signals from the global positioning system (GPS) radio navigation system for the measurement of sea surface roughness. This roughness has long been known to be dependent upon the surface wind speed. Experiments were conducted from aircraft along the TOPEX ground track and over experimental surface truth buoys. These flights used a receiver capable of recording the cross-correlation power in the reflected signal. The shape of this power distribution was then compared against analytical models, which employ a geometric optics approach. Two techniques for matching these functions were studied. The first recognized the most significant information content in the reflected signal is contained in the trailing edge slope of the waveform. The second attempted to match the complete shape of the waveform by approximating it as a series expansion and obtaining the nonlinear least squares estimate. Discussion is also presented on anomalies in the receiver operation and their identification and correction View full abstract»

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  • Progressive space frequency quantization for SAR data compression

    Publication Year: 2002 , Page(s): 3 - 10
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (613 KB) |  | HTML iconHTML  

    The authors propose a new wavelet image coding technique for synthetic aperture radar (SAR) data compression called a progressive space-frequency quantization (PSFQ). PSFQ performs spatial quantization via rate distortion-optimized zerotree pruning of wavelet coefficients that are coded using a progressive subband coding technique. They compared the performances of zerotree-based methods: EZW, SPIHT, SFQ, and PSFQ with the classical wavelet-based method (CWM), which uses uniform scalar quantization of subbands followed by recency rank coding. The performances of the methods based on zerotree quantization were better than the CWM in the rate distortion sense. The embedded coding techniques perform better SNR results than the methods using scalar quantization. However, the probability density function (PDF) of the reconstructed amplitude SAR data compressed using CWM, better corresponded to the PDF of the original data than the PDF of the reconstructed data compressed using the zerotree based methods. The amplitude PDF of the reconstructed data obtained using PSFQ compression algorithm better corresponded to the original PDF than the amplitude PDF of the data obtained using the multilook method View full abstract»

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  • Effects of random inhomogeneity on radar measurements and rain rate estimation

    Publication Year: 2002 , Page(s): 223 - 227
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (151 KB) |  | HTML iconHTML  

    The authors study the sampling effect on radar measurements of inhomogeneous media and the resultant rain estimation. A two-level drop size distribution (DSD) model is proposed, in which DSD parameters are assumed to be variable for representing the sampling effects. The dependence of statistical moments on the variation of DSD parameters are calculated and applied to radar-based rain estimation View full abstract»

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  • Error estimates for a histogram in scatterometer geophysical model function estimation

    Publication Year: 2002 , Page(s): 217 - 220
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (108 KB) |  | HTML iconHTML  

    The relationship between the normalized radar cross section σ° and the ocean surface wind field, i.e., the geophysical model function, is a key element in scatterometry. Due to many unsolved physical modeling problems, only a semi-empirical approach can be used to quantitatively relate the observed σ° to the wind field. Once the appropriate functional form has been selected, a model calibration procedure based on colocated σ° measurements and external wind field observations/determinations is accomplished. To this end, a σ° data grouping (binning) is performed to limit measurement uncertainties and reduce data volume. On this note, the binning procedure is revisited as an histogram estimation procedure and the relevant errors are determined. It is shown that in the best case of wind field error-free model the bias error introduced by the binning is negligible (but for low wind regimes) while the variance error is significant View full abstract»

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  • Comparison of two microwave radiobrightness models and validation with field measurements

    Publication Year: 2002 , Page(s): 143 - 152
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (136 KB)  

    This paper compares microwave brightness temperature (TB) estimated by two radiobrightness models: a multilayer coherent radiative transfer (CRT) model and a single-layer Fresnel reflectance model. Two dielectric mixing schemes were used along with the models to calculate permittivity (real part of the dielectric constant). Model TB and permittivity estimates were compared and validated against Huntsville, AL 1998 field experiment measurements. Model differences can be attributed to the mixing scheme, the radiobrightness model, or the vertical profile representation. Two sets of simulations were performed to quantify the sources of variation, one using observed son temperature and moisture profiles as input, and another using uniform profiles. Using uniform profiles, systematic differences in permittivity estimated by the mixing schemes resulted in TB differences as large as 15 K. However, for uniform profiles, differences in TB estimated by the radiobrightness models for a given permittivity value were less than 2 K. For cases using observed profiles, near-surface drying of the profiles resulted in TB values from the CRT model 6-10 K higher than estimates from the Fresnel model, which determines TB based on 0-5 cm mean moisture and temperature. Therefore, the major sources of TB variations were the dielectric mixing scheme and the shape of the near-surface moisture profile. No radiobrightness/mixing scheme combination exhibited superiority across all plots and times View full abstract»

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  • Haze detection and removal in high resolution satellite image with wavelet analysis

    Publication Year: 2002 , Page(s): 210 - 217
    Cited by:  Papers (18)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (319 KB) |  | HTML iconHTML  

    A procedure for haze detection and removal from high-resolution satellite images using wavelet analysis (HAWAT) has been developed. It involves the analysis of the low spatial frequency information content of a scene. The image contaminated by haze is decomposed into different spatial layers with wavelet transforms. Although haze is distributed in the lower frequency layer, this layer may also contain a component of land cover that is spatially and temporally relatively stable. A haze-free reference image of the same area is used to characterize land cover. The component of the characterized land cover is then subtracted with wavelet analysis. The residual wavelet coefficients are used to construct a spatially varying mask for subsequent haze detection and removal. After smoothing, the mask is subtracted from the contaminated image to obtain a corrected image with haze-off characteristics. Both visual inspection and statistical accuracy assessment show that the haze calibration is valid and robust View full abstract»

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  • Induction effects of 2-D structures on buried pipelines

    Publication Year: 2002 , Page(s): 197 - 205
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    The implementation of cathodic protection systems is very complicated since many factors can contribute for current flowing off the pipe. The design requires the characterization of the parameters impacting the corrosion process, such as soil resistivity, size of the pipe and quality of the coating. The authors study the effect of geomagnetic fields on the pipe-induced currents considering it as an additional cause of corrosion. A theoretical method previously implemented to model the currents induced on pipes embedded in homogeneous soils indicated a dependence between the intensity of the currents and the electrical resistivity of the soil, and predicted that a drainage of current through the pipe would occur at zones of shallow electrical discontinuities. They present another method for the calculation of the induced currents that allows the authors to consider also multilayered structures and lateral discontinuities in the Earth resistivity. Applying this method, they quantify the currents induced in pipelines embedded in different bidimensional structures in order to obtain an estimation of the effects produced by the presence of such kinds of terrains. They then applied this method to model measured data. Field work was performed along a 200 km-route of a pipeline system. In this zone, the pipe-to-soil potential was measured at different sites and a geophysical study was made to determine the discontinuities in soil resistivities. They obtained a correlation of the measured currents and soil resistivity consistent with the theoretical predictions View full abstract»

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  • Simulating coherent backscattering from crops during the growing cycle

    Publication Year: 2002 , Page(s): 162 - 177
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (337 KB) |  | HTML iconHTML  

    The backscattering coefficient and the position of interferometric phase center of wheat and sunflowers during the growing cycle have been computed by using a coherent electromagnetic model. In the model, the scattered fields are added coherently and the attenuation in the canopy is computed by means of Foldy's approximation. The comparison between model simulations and experimental data has shown that model results match reasonably well with the measured backscattering. As the plant grows, the backscattering of wheat ("narrow leaf" crop) decreases, whereas that of sunflowers ("broad leaf") increases. An analysis of the various terms that contribute to backscattering has indicated that the most significant contribution is given by the double scattering soil-stalk and that the position of the interferometric phase center is close to the soil. When the contribution of leaves is more significant, as in the case of sunflowers, the interferometric phase center goes up to about one quarter of the full plant height. This result demonstrates the potential of the interferometric observation in providing significant new information on crop classification algorithms based on scattering mechanisms View full abstract»

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  • Road detection in spaceborne SAR images using a genetic algorithm

    Publication Year: 2002 , Page(s): 22 - 29
    Cited by:  Papers (32)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (364 KB) |  | HTML iconHTML  

    This paper presents a technique for the detection of roads in a spaceborne synthetic aperture radar (SAR) image using a genetic algorithm (GA). Roads in a spaceborne SAR image can be modeled as curvilinear structures that possess width. Curve segments, which represent the candidate positions for roads, are extracted from the image using a curvilinear structure detector, and the roads are accurately detected by grouping those curve segments. For this purpose, the authors designed a grouping method based on a GA, which is a global optimization method. They combined perceptual grouping factors with it and tried to reduce its overall computational cost by introducing a concept of region growing. In this process, a selected initial seed is grown into a finally grouped segment by the iterated GA process, which considers segments only in a search region. To detect roads more accurately, postprocessing, including noisy curve segment removal, is performed after grouping. The authors applied their method to ERS-1 SAR and SIR-C/X-SAR images that have a resolution of about 30 m. The experimental results show that our method can accurately detect road networks as well as single-track roads and is much faster than a globally applied GA approach View full abstract»

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  • Frequency dependence of scattering by dense media of small particles based on Monte Carlo simulation of Maxwell equations

    Publication Year: 2002 , Page(s): 153 - 161
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (205 KB) |  | HTML iconHTML  

    The frequency dependence of extinction and scattering by geophysical medium at microwave frequencies is an important scattering topic because multifrequency measurements are used in remote sensing applications. Classical independent scattering theory states that if the particles are small, scattering is proportional to the fourth power in three-dimensional (3D) scattering and the third power in two-dimensional (2D) scattering. In this paper, the authors present Monte Carlo simulation results of dense media scattering. The dense media consists of densely packed small particles. Solutions are based on rigorous methods of generating dense media and subsequent numerical solutions of Maxwell's equation. Numerical simulations indicate that the frequency dependence of densely packed sticky particles is weaker than independent scattering View full abstract»

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  • Unsupervised segmentation of low clouds from infrared METEOSAT images based on a contextual spatio-temporal labeling approach

    Publication Year: 2002 , Page(s): 104 - 114
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (542 KB)  

    The early and accurate segmentation of low clouds during the night-time is an important task for nowcasting. It requires that observations can be acquired at a sufficient time rate as provided by the geostationary METEOSAT satellite over Europe. However, the information supplied by the single infrared METEOSAT channel available by night is not sufficient to discriminate between low clouds and ground during night from a single image. To tackle this issue, the authors consider several sources of information extracted from an infrared image sequence. Indeed, they exploit both relevant local motion-based measurements, intensity images and thermal parameters estimated over blocks, along with local contextual information. A statistical contextual labeling process in two classes, involving "low clouds" and "clear sky," is performed on the warmer pixels. It is formulated within a Bayesian estimation framework associated with Markov random field (MRF) models. This comes to minimize a global energy function comprising three terms: two data-driven terms (thermal and motion-based ones) and a regularization term expressing a priori knowledge on the label field (expected spatial contextual properties). The authors propose a progressive minimization procedure of this energy function starting from initial reliably labeled pixels and involving only local computation View full abstract»

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  • Landsat-4/5 Band 6 relative radiometry

    Publication Year: 2002 , Page(s): 206 - 210
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (175 KB) |  | HTML iconHTML  

    Relative radiometric responses for the thematic mapper (TM) band 6 data from Landsat-4 and Landsat-5 were analyzed, and an algorithm has been developed that significantly reduces the striping in Band 6 images due to detector mismatch. The TM internal calibration system as originally designed includes a DC restore circuit, which acts as a feedback system designed to keep detector bias at a constant value. There is a strong indication that the DC restore circuitry implemented in Band 6 does not function as it had been designed to. It operates as designed only during a portion of the calibration interval and not at all during acquisition of scene data. This renders the data acquired during the calibration shutter interval period virtually useless for correction of the individual responses of the four detectors in Band 6. It was observed and statistically quantified that the relative response of each of the detectors to the band average is stable over the dynamic range and throughout the lifetime of the instrument. This allows an alternate approach to relative radiometric correction of TM Band 6 images View full abstract»

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  • Finite-difference time-domain simulation of scattering from objects in continuous random media

    Publication Year: 2002 , Page(s): 178 - 186
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (198 KB)  

    A three-dimensional (3D) finite-difference time-domain (FDTD) scheme is introduced to model the scattering from objects in continuous random media. FDTD techniques have been previously applied to scattering from random rough surfaces and randomly placed objects in a homogeneous background, but little has been done to simulate continuous random media with embedded objects where volumetric scattering effects are important. In this work, Monte Carlo analysis is used in conjunction with FDTD to study the scattering from perfectly electrically conducting (PEC) objects embedded in continuous random media. The random medium models under consideration are chosen to be inhomogeneous soils with a spatially fluctuating random permittivities and prescribed correlation functions. The ability of frequency averaging techniques to discriminate objects in this scenarion is also briefly investigated. The simulation scheme described in this work can be adapted and used to help in interpreting the scattered field data from targets in random environments such as geophysical media, biological media, or atmospheric turbulence View full abstract»

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  • On the estimation of radar polarization orientation shifts induced by terrain slopes

    Publication Year: 2002 , Page(s): 30 - 41
    Cited by:  Papers (83)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (756 KB) |  | HTML iconHTML  

    In recent studies, D. L. Schuler et al. (2000) applied polarimetric imaging radar-derived orientation angles to measure topography, and J. S. Lee et al. (2000) used orientation angles for polarimetric SAR data compensation, to ensure accurate estimation of geophysical parameters in rugged terrain areas. To support these applications, it is important to accurately estimate shifts in orientation angles induced by the azimuth slope variations. However, in many cases, inconsistency in the estimation of orientation angle shifts was encountered in several areas, introducing noisy and erroneous results. The present authors develop a unified analysis of estimation algorithms based on the circular polarization covariance matrix. The concept of reflection symmetry is used to explain the soundness of the circular polarization method and to show problems associated with other algorithms. L-band polarimetric synthetic aperture radar (SAR) images of Camp Roberts, CA, are used to substantiate this theory View full abstract»

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  • Exact closed-form geolocation for SAR interferometry

    Publication Year: 2002 , Page(s): 220 - 222
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (101 KB)  

    Exact closed-form algorithms for InSAR-derived digital elevation model (DEM) geolocation are described. They are based on the knowledge of orbit parameters and time/Doppler frequency coordinates of each SAR image, as well as of their interferometric phase. The proposed scheme gives a simple framework for deriving the geolocation accuracy View full abstract»

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  • Direction interval retrieval with thresholded nudging: a method for improving the accuracy of QuikSCAT winds

    Publication Year: 2002 , Page(s): 79 - 89
    Cited by:  Papers (39)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (382 KB)  

    The SeaWinds scatterometer was developed by NASA JPL, Pasadena, CA, to measure the speed and direction of ocean surface winds. It was then launched onboard the QuikSCAT spacecraft. The accuracy of the majority of the swath and the size of the swath are such that the SeaWinds on QuikSCAT Mission (QSCAT) meets its science requirements despite shortcomings at certain cross-track positions. Nonetheless, it is desirable to modify the baseline processing in order to improve the quality of the less accurate portions of the swath, in particular near the far swath and nadir. Two disparate problems have been identified for these regions. At far swath, ambiguity removal skill is degraded due to the absence of inner beam measurements, limited azimuth diversity and boundary effects. Near nadir, due to nonoptimal measurement geometry, (measurement azimuths approximately 180° apart) there is a marked decrease in directional accuracy even when ambiguity removal works correctly. Two algorithms have been developed: direction interval retrieval (DIR) to address the nadir performance issue and thresholded nudging (TN) to improve ambiguity removal at far swath. The authors illustrate the impact of the two techniques by exhibiting prelaunch simulation results and postlaunch statistical performance metrics with respect to ECMWF wind fields and buoy data View full abstract»

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  • Analysis of interannual changes in northern vegetation activity observed in AVHRR data from 1981 to 1994

    Publication Year: 2002 , Page(s): 115 - 130
    Cited by:  Papers (53)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (601 KB)  

    This paper reports on the analysis of Pathfinder AVHRR land (PAL) data set that spans the period July 1981 to September 1994. The time series of normalized difference vegetation index (NDVI) data for land areas north of 45° N assembled by correcting the PAL data with spectral methods confirms the northerly greening trend and extension of the photosynthetically active growing season. Analysis of the channel reflectance data indicates that the interannual changes in red and near-infrared reflectances are similar to seasonal changes in the spring time period when green leaf area increases and photosynthetic activity ramps up. Model calculations and theoretical analysis of the sensitivity of NDVI to background reflectance variations confirm the hypothesis that warming driven reductions in snow cover extent and earlier onset of greening are responsible for the observed changes in spectral reflectances over vegetated land areas View full abstract»

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  • SeaWiFS ocean color data archive and distribution system: assessment of system performance

    Publication Year: 2002 , Page(s): 90 - 103
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (531 KB) |  | HTML iconHTML  

    The Sea-viewing Wide Field-of View Sensor (SeaWiFS) Mission has initiated a new era of ocean color remote sensing and has established performance benchmarks that will be emulated by subsequent missions. An integral element of the SeaWiFS mission is the data component, performed by the Goddard Earth Sciences Distributed Active Archive Center (GES DAAC), NASA Goddard Space Flight Center, Greenbelt, MD. Since the beginning of data distribution in September 1997, the GES DAAC has managed the data archive and improved data distribution capability. SeaWiFS data products are archived in a primary, secondary, and tertiary archive structure, ensuring data preservation. Data distribution utilizes a World Wide Web (WWW)-based ordering interface, allowing distribution either electronically or on magnetic tape media. Automatic data subscriptions, supplying user-tailored data product selections, have yielded a high archive-to-distribution ratio. System improvements have increased efficiency and redundancy. The user interface has added features designed to facilitate data access and data usage, enhanced by WWW information resources and comprehensive online dataset documentation. As SeaWiFS enters the latter half of its five-year mission, a system performance assessment provides useful information for other Earth remote sensing missions and allows consideration of future usage objectives for the SeaWiFS data archive View full abstract»

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  • A theoretical study of sea surface up/down wind brightness temperature differences

    Publication Year: 2002 , Page(s): 66 - 78
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB) |  | HTML iconHTML  

    The small slope approximation (SSA) for polarimetric thermal emission from a rough surface is applied to study the up/down wind difference of sea surface brightness temperatures. A complete third-order theory is used, with results expressed in terms of an integral over the sea surface bispectrum. An approximation is developed to obtain emission contributions for surface length scales much larger than the electromagnetic wavelength and in this limit, the up/down wind brightness temperature difference is determined entirely by a combination of third moments of surface slope. Polarization dependencies in this limit however do not match those obtained from the Jet Propulsion Laboratory (JPL) WindRAD empirical model. Another approximation is derived to capture up/down wind emission asymmetry due to short waves which are modulated by longer waves. In this case, an integral of emission "weighting functions" over a pair of "reduced" bispectra is obtained, and examination of the weighting functions shows the importance of surface length scales comparable to the electromagnetic wavelength. The polarization dependencies of these weighting functions illustrate the possibility of matching the WindRAD model, but the absence of an effective hydrodynamic model for short gravity-capillary wave modulation by longer waves limits detailed comparisons View full abstract»

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  • Minimum mean square error space-varying filtering of interferometric SAR data

    Publication Year: 2002 , Page(s): 11 - 21
    Cited by:  Papers (8)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (644 KB) |  | HTML iconHTML  

    This paper addresses the problem of filtering interferometric synthetic aperture radar (IFSAR) signals in presence of nonplanar topography to mitigate geometrical decorrelation effects. The problem is space-variant. The authors assume knowledge about the scene topography and derive an optimal, minimum mean square error (MMSE), filtering procedure. The algorithm is flexible and, beside the standard stripmap-stripmap interferometry, it may be applied to IFSAR data acquired in any operative mode. For instance, in scan-scan, scan-strip, and scan-spot interferometry. The scene topography contribution may be either derived from an external rough digital elevation model (DEM) or directly estimated from the SAR data. The filtering technique is extended to the azimuth direction to account for possible Doppler centroid decorrelation. Experimental results carried out on real data confirm the validity of the theory and show that this filtering procedure allows the authors to obtain a reduction of the interferometric noise content. Its gain is particularly marked in the cases of steep topography, where application of the standard common band filters could deteriorate the signal quality, or for large Doppler centroid shifts between the two acquisitions View full abstract»

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  • Influence of microphysical cloud parameterizations on microwave brightness temperatures

    Publication Year: 2002 , Page(s): 187 - 196
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (210 KB)  

    The microphysical parameterization of clouds and rain cells plays a central role in atmospheric forward radiative transfer models used in calculating microwave brightness temperatures. The absorption and scattering properties of a hydrometeor-laden atmosphere are governed by particle phase, size distribution, aggregate density, shape, and dielectric constant. This study investigates the sensitivity of brightness temperatures with respect to the microphysical cloud parameterization. Calculated wideband (6-410 GHz) brightness temperatures were studied for four evolutionary stages of an oceanic convective storm using a rive-phase hydrometeor model in a planar-stratified scattering-based radiative transfer model. Five other microphysical cloud parameterizations were compared to the baseline calculations to evaluate brightness temperature sensitivity to gross changes in the hydrometeor size distributions and the ice-air-water ratios in the frozen or partly frozen phase. The comparison shows that enlarging the raindrop size or adding water to the partly frozen hydrometeor mix warms brightness temperatures by as much as 55 K at 6 GHz. The cooling signature caused by ice scattering intensifies with increasing ice concentrations and at higher frequencies. An additional comparison to measured Convection and Moisture Experiment (CAMEX-3) brightness temperatures shows that in general all but two parameterizations produce calculated TBs that fall within the CAMEX-3 observed minima and maxima View full abstract»

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  • Interband calibration over clouds for POLDER space sensor

    Publication Year: 2002 , Page(s): 131 - 142
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (319 KB)  

    The Polarization and Directionality of the Earth's Reflectance (POLDER) spatial polarimeter was onboard the Advanced Earth Observation Satellite (ADEOS) satellite that flew from August 1996 to June 30, 1997. POLDER measured both multidirectional reflectance and polarization in visible and near-infrared spectral bands with a very wide field of view. An accurate absolute radiometric calibration is essential for the scientific exploitation of radiance measurements of the Earth. POLDER inflight radiometric calibration has been performed at the Centre National d'Etudes Spatiales (CNES), French National Space Studies Center, from measurements taken only on well-characterized targets. This paper presents the results of the POLDER in-flight radiometric interband calibration over clouds for channels 443 and 490 nm. The method is based on the comparison of measurements to simulations. Selected measurements correspond to observations over oceans for high, thick convective cumulonimbus and for low, thick stratocumulus. Simulations are calculated using the discrete ordinate computing method. An error budget considers the sensitivity of this calibration method to cloud microphysics, to cloud top altitude, and to aerosols and gaseous loading. Calibration results are discussed for different simulated cloud models 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.

 

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Meet Our Editors

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