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Geoscience and Remote Sensing, IEEE Transactions on

Issue 1  Part 2 • Date Jan. 2009

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Displaying Results 1 - 21 of 21
  • [Front cover]

    Publication Year: 2009 , Page(s): C1
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  • IEEE Transactions on Geoscience and Remote Sensing publication information

    Publication Year: 2009 , Page(s): C2
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  • Table of contents

    Publication Year: 2009 , Page(s): 189 - 190
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  • DEM Reconstruction Accuracy in Multichannel SAR Interferometry

    Publication Year: 2009 , Page(s): 191 - 201
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (867 KB) |  | HTML iconHTML  

    Interferometric synthetic aperture radar (InSAR) systems allow the estimation of the height profile of the Earth surface. When the height profile of the observed scene is characterized by high slopes or exhibits strong height discontinuities, the height reconstruction obtained from a single interferogram is ambiguous, since the solution of the estimation problem is not unique. To solve this ambiguity and restore the solution uniqueness, multiple interferograms, obtained with different baselines and/or with different frequencies, have to be used (multichannel InSAR). The height profile can then be estimated from multiple interferograms using maximum likelihood (ML) estimation techniques or by means of maximum a posteriori (MAP) estimation techniques, which take into account the relation between adjacent pixels. In this paper, the height estimation accuracy achievable with a given multibaseline interferometric configuration and using the aforementioned estimation techniques in terms of Cramer-Rao lower bound for the ML and of error lower bound for the MAP, is analyzed and discussed. It is shown that the MAP technique outperforms the ML one and that its attainable accuracy is not sensitive to the baselines choice, while mainly depends on the ground slopes. View full abstract»

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  • Improved Sigma Filter for Speckle Filtering of SAR Imagery

    Publication Year: 2009 , Page(s): 202 - 213
    Cited by:  Papers (68)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1609 KB) |  | HTML iconHTML  

    The Lee sigma filter was developed in 1983 based on the simple concept of two-sigma probability, and it was reasonably effective in speckle filtering. However, deficiencies were discovered in producing biased estimation and in blurring and depressing strong reflected targets. The advancement of synthetic aperture radar (SAR) technology with high-resolution data of large dimensions demands better and efficient speckle filtering algorithms. In this paper, we extend and improve the Lee sigma filter by eliminating these deficiencies. The bias problem is solved by redefining the sigma range based on the speckle probability density functions. To mitigate the problems of blurring and depressing strong reflective scatterers, a target signature preservation technique is developed. In addition, we incorporate the minimum-mean-square-error estimator for adaptive speckle reduction. Simulated SAR data are used to quantitatively evaluate the characteristics of this improved sigma filter and to validate its effectiveness. The proposed algorithm is applied to spaceborne and airborne SAR data to demonstrate its overall speckle filtering characteristics as compared with other algorithms. This improved sigma filter remains simple in concept and is computationally efficient but without the deficiencies of the original Lee sigma filter. View full abstract»

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  • LMMSE 3-D SAR Focusing

    Publication Year: 2009 , Page(s): 214 - 223
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (870 KB) |  | HTML iconHTML  

    Three-dimensional synthetic aperture radar (SAR) imaging, a technique also known as SAR tomography, uses multiple views to extend the capability of SAR systems to 3-D imaging by achieving a profiling of the scattering power at different heights. Multiple views are obtained with the current satellite technology via successive passes of a single antenna SAR sensor over the same scene, but next-generation sensor formations are foreseen to acquire multistatic data. Conventional processing, such as the beamforming, or singular values decomposition inversion is based on geometrical derivations and, hence, assumes the accurate phase calibration and the absence of target decorrelation. This paper analyzes the effects of phase miscalibration due to residual uncompensated atmospheric contribution and temporal decorrelation and proposes a 3-D imaging technique based on a linear minimum mean square error approach. The resulting algorithm extends the possibilities of the conventional processing by carrying out an integration of data that accounts for the a priori data correlation properties. Hence, it allows handling of the presence of additional stochastic contributions such as: temporal coherence losses and atmospheric phase miscalibration. Moreover, with reference to future bistatic and multistatic systems, it permits an improved coherent integration of data acquired by simultaneous antenna in repeated passes. View full abstract»

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  • Four-Dimensional SAR Imaging for Height Estimation and Monitoring of Single and Double Scatterers

    Publication Year: 2009 , Page(s): 224 - 237
    Cited by:  Papers (61)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2264 KB) |  | HTML iconHTML  

    The superposition of contributions from different stable targets within the same pixel is a phenomenon that may impair the imaging and monitoring of ground scatterers via the multipass synthetic aperture radar (SAR) interferometry technique. Three-dimensional SAR imaging, also known as SAR tomography, uses multiple views to profile the scattering power at different heights. This technique has been shown to be capable of separating interfering target responses on real data. Differential SAR tomography has been recently proposed as a technique that extends the potentialities of SAR tomography to the target deformation monitoring. It performs a 4-D space-velocity imaging that enables not only separating interfering targets in elevation but also distinguishing their single slow deformation velocities. This work addresses for the first time the application of 4-D SAR imaging to real data to determine the height and mean deformation velocity of single scatterers and double-scattering mechanisms interfering at high resolution in the same pixel. It also discusses the postprocessing steps required to identify the presence of stable single and double scatterers after elevation-velocity focusing. Moreover, it proposes a technique for the extraction of time series from interfering targets to measure possible nonlinear temporal deformations. View full abstract»

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  • Omega-k Algorithm for Airborne Spatial Invariant Bistatic Spotlight SAR Imaging

    Publication Year: 2009 , Page(s): 238 - 250
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (605 KB) |  | HTML iconHTML  

    Bistatic spotlight synthetic aperture radar (SAR) which uses a separated transmitter and receiver has been studied intensively due to its flexibility. To reconstruct the image for the bistatic SAR in the parallel track configuration, where the transmitter and the receiver have equal velocity, we modify the omega-k algorithm. Specifically, using the extended Taylor approximation (ETA), we convert the parallel track configuration into the single track configuration. Then, using the principle of the stationary phase, we propose an analytical method to increase the image quality of bistatic SAR systems. View full abstract»

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  • Installation of a Doppler Radar Monitoring System at Merapi Volcano, Indonesia

    Publication Year: 2009 , Page(s): 251 - 271
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3055 KB) |  | HTML iconHTML  

    Merapi Volcano, Indonesia, is one of the most active dome building volcanoes worldwide. Instabilities at the growing dome cause rockfalls and hot block and ash flows, which can reach run-out distances of several kilometers. Therefore, Merapi has been monitored extensively for many years. However, direct visual observation of the dome is often impossible due to cloud coverage of the summit. In October 2001, a first prototype Doppler radar system was installed to overcome this shortcoming. The system is able to penetrate clouds and observe material movements at the dome, giving valuable information about dynamic processes in the dome area. The system also allows detection of rainfall in several distance intervals. For precise positioning of the beam, the system was equipped with an electromechanical mounting in 2003. A charge-coupled device (CCD) camera attached to the radar mirror documents the radar beam position and provides visual observation of the dome. Recorded data, camera images, and status information are telemetered to the Merapi Volcano Observatory, where they can be processed and interpreted. Status information is also sent via short message service via a global system for mobile communications (GSM) modem. By processing the Doppler radar data, we are able to discriminate between three different types of instability events: sliding dome material, dome material gravitationally breaking off the dome, and explosive outbursts of dome material due to expansion of volcanic gas. In order to independently verify our observations, we compared rockfall events detected by the radar system to seismic recordings and found a good correlation. View full abstract»

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  • On the Use of Auxiliary Receive Channels for Clutter Mitigation With Phased Array Weather Radars

    Publication Year: 2009 , Page(s): 272 - 284
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3025 KB) |  | HTML iconHTML  

    Phased array radars (PARs) are attractive in weather surveillance primarily because of their capability to electronically steer. When combined with the recently developed beam multiplexing (BMX) technique, these radars can obtain very rapid update scans that are useful in monitoring severe weather. A consequence is that the small number of contiguous samples of the time series obtained can be a challenge for temporal/spectral filters used for clutter mitigation. As a result, the accurate extraction of weather signals can become the limiting performance barrier for PARs that employ BMX in clutter-dominated scattering fields. By exploiting the spatial correlation of the auxiliary channel signals, the effect of clutter contamination can be reduced in these conditions. In this paper, three spatial filtering techniques that used low-gain auxiliary receive channels are presented. The effect of clutter mitigation was studied using numerical simulations of a tornadic environment for changes in signal-to-noise ratio, clutter-to-signal ratio, number of time series samples, varying clutter spectral widths, and maximum weight constraints. Since such data are not currently available from a horizontally pointed phased array weather radar, experimental validation was applied to an existing data set from the turbulent eddy profiler, which is a vertically pointed PAR. Although preliminary, the results show promise for clutter mitigation with extremely short nonuniform sampling. View full abstract»

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  • Brightness-Temperature Retrieval Methods in Synthetic Aperture Radiometers

    Publication Year: 2009 , Page(s): 285 - 294
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1362 KB) |  | HTML iconHTML  

    Brightness-temperature retrieval techniques for synthetic aperture radiometers are reviewed. Three different approaches to combine measured visibility and antenna temperatures, along with instrument characterization data, into a general equation to invert are presented. Discretization and windowing techniques are briefly discussed, and formulas for reciprocal grids using rectangular and hexagonal samplings are given. Two known techniques are used to invert the equation, namely, inverse Fourier transform and G -matrix pseudoinverse. The proposed preprocessing approaches combined with these two inversion methods are implemented with real data measured by an airborne Y-shaped interferometric radiometer over land and water, and are compared. The images indicate that best results are obtained when inverting an incremental visibility obtained after substracting a term that includes the individual antenna temperatures, the physical temperatures of the receivers, and a flat-target response directly measured from cold-sky looks. View full abstract»

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  • Validation of a New Parametric Model for Atmospheric Correction of Thermal Infrared Data

    Publication Year: 2009 , Page(s): 295 - 311
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1961 KB) |  | HTML iconHTML  

    Surface temperature is a key component for understanding energy fluxes between the Earth's surface and atmosphere. Accurate retrieval of surface temperature from satellite observations requires proper correction of the thermal channels for atmospheric emission and attenuation. Although the split-window method has offered relatively accurate measurements, this empirical approach requires in situ data and will only perform well if the in situ data are from the same surface type and similar climatology. Single channel correction reduces uncertainty inherent to the split-window method, but requires an accurate radiative transfer model and description of the atmospheric profile. Unfortunately, this method is impractical for operational correction of satellite retrievals due to the size of data sets and computation time required by radiative transfer modeling. We present a thermal parametric model based upon the MODTRAN radiative transfer code and tuned to Moderate Resolution Imaging Spectrometer (MODIS) channels. Comparison with MODTRAN showed a good performance for the parametric model and computation speeds approximately three orders of magnitude faster. Sea surface temperature (SST) calculated using atmospheric correction parameters generated from our model showed consistent results (rmse = 0.49 K) and small bias (-0.45 K) with the MODIS SST product (MYD28). Validation of surface temperatures derived using our model with in situ land and water temperature measurements exhibited accuracy (mean bias < 0.35 K) and low error (rmse < 1 K) for MODIS bands 31 and 32. Finally, an investigation of profile sources and their effect on atmospheric correction offered insight into the application of the parametric model for operational correction of MODIS thermal bands. View full abstract»

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  • GPS-Based Radio Tomography With Edge-Preserving Regularization

    Publication Year: 2009 , Page(s): 312 - 324
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (734 KB) |  | HTML iconHTML  

    A tomographic forward and inverse model is presented for deriving 3-D images of ionospheric electron density from ground-based dual-frequency Global Positioning System (GPS) measurements and ionosonde data. The GPS observation geometry is discretely modeled, and a linear algebraic relationship is derived between the integrated electron density measurements and the ionospheric electron density. Because the inverse problem is ill conditioned, regularization is used to stabilize the solution in the presence of noise. In this paper, we regularize the inverse problem by incorporating neighborhood smoothness and continuity constraints applicable to general ionospheric conditions. To avoid oversmoothing of edges, nonconvex regularizing functionals are used to capture potential localized ionospheric density structures. A deterministic relaxation technique is used to minimize the proposed cost function. The specific formulation of the reconstruction geometry is directly related to the sparseness and the nonuniform distribution of the GPS ray paths. The grid boundaries, the regularization parameters, the model order, and the grid placement are selected in conjunction with available remote sensing data and appropriate optimality criteria. The algorithm is tested using simulations of ionospheric structures with actual GPS observation geometry. These simulations demonstrate the effectiveness in detecting and reconstructing ionospheric height and density fluctuations, and illustrate the statistical performance and bounds of the inversion technique. View full abstract»

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  • Microwave Emission Observations from Artificial Thin Sea Ice: The Ice-Tank Experiment

    Publication Year: 2009 , Page(s): 325 - 338
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3054 KB) |  | HTML iconHTML  

    Simulated sea ice was grown in an outdoor tank during the early winter seasons of 2001/2002 and 2005/2006. Microwave radiation was sampled every 5 min from the following three channels: 19, 37, and 85 GHz. Surface physical conditions were measured or observed to help in the interpretation of the radiometric behavior. This paper reports on results related to the following objectives: 1) linking the observed radiation to surface properties and processes; 2) classifying thin ice into emissivity-based surface types, and 3) assessing thin-ice parameter retrieval algorithms. This paper shows that ice of less than 4-cm thickness exhibits cycles of a sharp decrease of microwave emission caused by surface wetness followed by a gradual increase as the surface refreezes. This ice is particularly linked to meteorological conditions. Snow accumulation on relatively thick ice (> 20 cm) affects only the radiation from the 85-GHz channel. Thin-ice surfaces can be grouped into two radiometrically distinguished categories - the first includes slushy and wet surfaces and the second includes wet snow, dry snow, and dry bare-ice surfaces. Radiation from the second category is higher. The radiation from a refrozen slush surface appears to fall between these two categories. The variability of emissivity increases as the radiation frequency increases, particularly for the horizontal polarization channels. Existing algorithms of ice thickness, snow depth, and ice concentration were examined against the current data to study their sensitivity to variations of surface conditions. Limitations on their applications have been established. View full abstract»

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  • Revision of the Single-Channel Algorithm for Land Surface Temperature Retrieval From Landsat Thermal-Infrared Data

    Publication Year: 2009 , Page(s): 339 - 349
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (820 KB) |  | HTML iconHTML  

    This paper presents a revision, an update, and an extension of the generalized single-channel (SC) algorithm developed by Jimenez-Munoz and Sobrino (2003), which was particularized to the thermal-infrared (TIR) channel (band 6) located in the Landsat-5 Thematic Mapper (TM) sensor. The SC algorithm relies on the concept of atmospheric functions (AFs) which are dependent on atmospheric transmissivity and upwelling and downwelling atmospheric radiances. These AFs are fitted versus the atmospheric water vapor content for operational purposes. In this paper, we present updated fits using MODTRAN 4 radiative transfer code, and we also extend the application of the SC algorithm to the TIR channel of the TM sensor onboard the Landsat-4 platform and the enhanced TM plus sensor onboard the Landsat-7 platform. Five different atmospheric sounding databases have been considered to create simulated data used for retrieving AFs and to test the algorithm. The test from independent simulated data provided root mean square error (rmse) values below 1 K in most cases when atmospheric water vapor content is lower than 2 g middotcm-2. For values higher than 3 g middotcm-2, errors are not acceptable, as what occurs with other SC algorithms. Results were also tested using a land surface temperature map obtained from one Landsat-5 image acquired over an agricultural area using inversion of the radiative transfer equation and the atmospheric profile measured in situ at the sensor overpass time. The comparison with this ldquoground-truthrdquo map provided an rmse of 1.5 K. View full abstract»

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  • Land Surface Temperature From the Advanced Along-Track Scanning Radiometer: Validation Over Inland Waters and Vegetated Surfaces

    Publication Year: 2009 , Page(s): 350 - 360
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (875 KB) |  | HTML iconHTML  

    The land surface temperature (LST) product of the Advanced Along-Track Scanning Radiometer (AATSR) was validated with ground measurements at the following two thermally homogeneous sites: Lake Tahoe, CA/NV, USA, and a large rice field close to Valencia, Spain. The AATSR LST product is based on the split-window technique using the 11- and 12- mum channels. The algorithm coefficients are provided for 13 different land-cover classes plus one lake class (index i). Coefficients are weighted by the vegetation-cover fraction (f). In the operational implementation of the algorithm, i and f are assigned from a global classification and monthly fractional vegetation-cover maps with spatial resolutions of 0.5deg times 0.5deg. Since the validation sites are smaller than this, they are misclassified in the LST product and treated incorrectly despite the fact that the higher resolution AATSR data easily resolve the sites. Due to this problem, the coefficients for the correct cover types were manually applied to the AATSR standard brightness temperature at sensor product to obtain the LST for the sites assuming they had been correctly classified. The comparison between the ground-measured and the AATSR-derived LSTs showed an excellent agreement for both sites, with nearly zero average biases and standard deviations les 0.5degC. In order to produce accurate and precise estimates of LST, it is necessary that the land-cover classification is revised and provided at the same resolution as the AATSR data, i.e., 1 km rather than the 0.5deg resolution auxiliary data currently used in the LST product. View full abstract»

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  • The Closed-Form Solution to the Reconstruction of the Radiating Current for EM Inverse Scattering

    Publication Year: 2009 , Page(s): 361 - 369
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (602 KB) |  | HTML iconHTML  

    The closed-form solution to the reconstruction of radiating current with a line measurement configuration is presented in this paper. The analytical result of the continuous singular value decomposition of the scattering integral operator is derived and used to analyze the imaging resolution and reconstruct the radiating component of the equivalent current density. The main four advantages of the proposed closed-form solution are as follows: 1) The reconstruction of radiating current can be achieved in a very short computation time; 2) it is quite tolerant to different levels of noises; 3) it is very easy to realize the reconstruction of radiating currents within the obstacles embedded in layered medium; and 4) the imaging resolution kernel of the scattering operator can also be derived in a closed form. Numerical simulations show the high efficiency of the proposed method for the reconstruction of radiating current. View full abstract»

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  • Gravity Probe-B: New Methods to Determine Spin Parameters From kHz SLR Data

    Publication Year: 2009 , Page(s): 370 - 375
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1044 KB) |  | HTML iconHTML  

    Using kilohertz data of the satellite laser ranging (SLR) station Graz only, the spin parameters of the Gravity Probe-B (GP-B) satellite are derived; these include the spin period over the course of the 1.5-year mission period, as well as spin direction and spin axis orientation. The results are compared to the actual data sets-as determined by the GP-B mission itself-thus allowing independent confirmation of the kilohertz SLR derived results. View full abstract»

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    Publication Year: 2009 , Page(s): 376
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  • IEEE Transactions on Geoscience and Remote Sensing information for authors

    Publication Year: 2009 , Page(s): C3
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    Publication Year: 2009 , Page(s): C4
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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