By Topic

Geoscience and Remote Sensing Letters, IEEE

Issue 3 • Date May 2011

Filter Results

Displaying Results 1 - 25 of 45
  • [Front cover]

    Page(s): C1
    Save to Project icon | Request Permissions | PDF file iconPDF (182 KB)  
    Freely Available from IEEE
  • IEEE Geoscience and Remote Sensing Letters publication information

    Page(s): C2
    Save to Project icon | Request Permissions | PDF file iconPDF (41 KB)  
    Freely Available from IEEE
  • Table of contents

    Page(s): 389 - 390
    Save to Project icon | Request Permissions | PDF file iconPDF (53 KB)  
    Freely Available from IEEE
  • Ship Detection in Ice-Infested Waters Based on Dual-Polarization SAR Imagery

    Page(s): 391 - 395
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (779 KB) |  | HTML iconHTML  

    This letter discusses the potential of automatic ship detection in ice-infested waters based on satellite synthetic aperture radar (SAR) imagery. The popular K -distribution is used to model the backscatter statistics of sea ice clutter. The goodness of fit of this model is assessed with the Kolmogorov-Smirnov and Anderson-Darling test statistics for both VV and VH polarizations. We also test the impact of introducing the Method of Log Cumulant (MoLC) estimator for the shape parameter of the K-distribution. Finally, a constant false-alarm rate ship detection algorithm, applying the K -distribution with the MoLC estimator, is evaluated on dual-polarization RADARSAT-2 SAR data. Our results demonstrate that this is a viable approach to ship detection in ice-infested waters. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Time-Domain Reconstruction Algorithms for FMCW-SAR

    Page(s): 396 - 400
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB) |  | HTML iconHTML  

    In this letter, we develop time-domain reconstruction algorithms for frequency-modulated continuous wave synthetic aperture radar (FMCW-SAR). The algorithms considered here are the time-domain correlation algorithm, and two versions of the backprojection algorithm: the standard one based on the start-stop approximation, and a modified version that takes into account the movement of the sensor during the transmission of the pulse. Numerical simulations illustrate the performance of the algorithms, showing that the start-stop approximation may not be valid for FMCW-SAR, whereas the modified backprojection algorithm works very well here. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • CloudSat W-Band Radar Measurements of Surface Backscatter

    Page(s): 401 - 405
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (665 KB) |  | HTML iconHTML  

    The authors examine the characteristics of the W-band surface backscatter cross section using data from the 94-GHz cloud profiling radar on the CloudSat mission. These data from CloudSat represent the first global measurements of surface properties at 94 GHz. The authors use these data to investigate seasonal changes in surface backscatter over both land and ocean. The authors also make use of a limited set of off-nadir data to investigate behavior of W-band backscatter from the ocean versus wind speed for incidence angles up to 17°. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multispectral Image Matching Using Rotation-Invariant Distance

    Page(s): 406 - 410
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (330 KB) |  | HTML iconHTML  

    Normalized cross correlation (NCC) has been widely used to match control points (CP) in image alignment. This method will produce a lot of incorrect matches owing to the significant difference in the image intensity between multispectral image pairs, and furthermore, it is very computationally expensive to handle rotational displacement. This letter presents a method using rotation-invariant distance to match CPs; a local descriptor matrix is built to describe each CP, and fast Fourier transform is introduced to compute the rotation-invariant distance between the matrices. The computational load is sharply decreased by rotation-invariant distance compared to NCC, and furthermore, the load will remain unchanged in circumstance with arbitrary rotational angle. Experimental results indicate that the proposed method improves the match performance compared to other state-of-the-art methods in terms of correct match rate and aligning accuracy. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Micro-Doppler Signature Extraction and ISAR Imaging for Target With Micromotion Dynamics

    Page(s): 411 - 415
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB) |  | HTML iconHTML  

    The micromotion of a target will generate a micro-Doppler (m-D) effect in the frequency domain. The m-D effect is regarded as a unique property of the target, which has special significance in target detection, identification, and classification. The classical range-Doppler algorithm cannot obtain a clear inverse synthetic aperture radar (ISAR) image due to the m-D effect induced by micromotion dynamics. The m-D effect induced by periodical micromotion is represented as a sinusoidal modulation in a spectrogram, whereas the Doppler induced by a main body is depicted as the form of a straight line. Therefore, the extraction of an m-D signature is transformed into the separation of a sinusoid and a straight line. The cancellation technique is a classical method for removing ground clutter. Based on the same principle, the cancellation technique is applied to the spectrogram in this letter, which successfully achieves the separation of the m-D signature and gets the clearer ISAR image of the main body. The effectiveness and robustness of the algorithm are proved by simulation results. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multitemporal Hyperspectral Image Compression

    Page(s): 416 - 420
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB) |  | HTML iconHTML  

    The compression of multitemporal hyperspectral imagery is considered, wherein the encoder uses a reference image to effectuate temporal decorrelation for the coding of the current image. Both linear prediction and a spectral concatenation of images are explored to this end. Experimental results demonstrate that, when there are few changes between two images, the gain in rate-distortion performance is achieved over the independent coding of the current image. In addition, a strategy that explicitly removes salient temporal changes and stores them losslessly in the bitstream is proposed, and it is observed that this change-removal process results in a slight decrease in the rate-distortion performance with the benefit of perfect representation of the changed pixels. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Microwave Imaging of Soil Water Diffusion Using the Linear Sampling Method

    Page(s): 421 - 425
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (402 KB) |  | HTML iconHTML  

    This letter deals with the monitoring of the volumetric water content of a soil column in a fully controlled environment by means of a noninvasive microwave imaging system. Indeed, soil moisture is an important piece of information to improve fluid flow modeling or to better understand the water uptake by plant roots. In this letter, we address the problem of recovering the footprint of soil moisture evolution with respect to time using a built-in laboratory microwave setup coupled to a robust qualitative microwave imaging method: the linear sampling method (LSM). The evolution of the water content in the soil is ruled by the Richards equations and stored at different time steps. The associated maps of soil water content are converted into permittivity maps using the Dobson model. Electromagnetic scattered fields are then computed with finite-element software. We have tested the LSM in a situation that can be encountered in agricultural soils where the water content is not homogeneous. We show that the evolution of the soil water content can be qualitatively monitored with the LSM. We also point out that the source is more precisely located by considering the evolution in time of the singular system of the multistatic matrix (multiple signal classification method). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Mini-UAV-Borne LIDAR for Fine-Scale Mapping

    Page(s): 426 - 430
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (457 KB) |  | HTML iconHTML  

    Light detection and ranging (LIDAR) systems based on unmanned aerial vehicles (UAVs) recently are in rapid advancement, while mini-UAV-borne laser scanning has few reported progress, notwithstanding so extensively required. This study established a pioneered mini-UAV-borne LIDAR system - Sensei, schematically with an Ibeo Lux scanner mounted on a small Align T-Rex 600E helicopter. Furthermore, the associated data processing involved in the coordinate triple, pulse intensity, and multiechoes per pulse was explored to validate its applicability for fine-scale mapping, in terms of, e.g., tree height estimation, pole detection, road extraction, and digital terrain model refinement. The feasibility and advantages of mini-UAV-borne LIDAR have been demonstrated by the promising results based on the real-measured data. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Support Vector Machine Active Learning Through Significance Space Construction

    Page(s): 431 - 435
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (572 KB) |  | HTML iconHTML  

    Active learning is showing to be a useful approach to improve the efficiency of the classification process for remote sensing images. This letter introduces a new active learning strategy specifically developed for support vector machine (SVM) classification. It relies on the idea of the following: 1) reformulating the original classification problem into a new problem where it is needed to discriminate between significant and nonsignificant samples, according to a concept of significance which is proper to the SVM theory; and 2) constructing the corresponding significance space to suitably guide the selection of the samples potentially useful to better deal with the original classification problem. Experiments were conducted on both multi- and hyperspectral images. Results show interesting advantages of the proposed method in terms of convergence speed, stability, and sparseness. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The Influence of the Inverted Sea Wave Theories on the Derivation of Coastal Bathymetry

    Page(s): 436 - 440
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (613 KB) |  | HTML iconHTML  

    The estimation of nearshore bathymetry by inverting the wave dispersion function is an accepted method. The performance of four different wave theories inverted with dispersive surface classificator for the derivation of the bathymetry is examined during gale oceanographic conditions. The physical and technical limitations for the inversion are taken into consideration. The analyzed data are radar image sequences, and ground truth is an in situ echosounder's bathymetry data set. All geomorphological features detectable with a 41-m spatial resolution have been identified, but there is an underestimation of the absolute depth. The applicable theories have mean error less than 7%. The nonlinear theories are compared with the linear theory, and the experimental difference of their performance is on the order of the theoretical expectation O (6%-8%). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Adaptive InSAR Stack Multilooking Exploiting Amplitude Statistics: A Comparison Between Different Techniques and Practical Results

    Page(s): 441 - 445
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (663 KB) |  | HTML iconHTML  

    Efficient estimation of the interferometric phase and complex correlation is fundamental for the full exploitation of interferometric synthetic aperture radar (InSAR) capabilities. Particularly, when combining interferometric measures arising both from distributed and concentrated targets, the interferometric phase has to be correctly extracted in order to preserve its physical meaning. Recently, an amplitude-based algorithm for the adaptive multilooking of InSAR stacks was proposed where it was shown that a comparison of the backscatter amplitude statistics is a suitable way to adaptively group and average the pixels in order to preserve the phase signatures of natural structures in the observed area. In this letter, different methods to compare amplitude statistics will be presented, compared through simulation and applied to real data. Based on these, recommendations are made concerning which method to use in practice. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Extended NCS Based on Method of Series Reversion for Imaging of Highly Squinted SAR

    Page(s): 446 - 450
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (183 KB) |  | HTML iconHTML  

    In the case of high range resolution and squint angle, current chirp scaling algorithm (CSA) and nonlinear CSA (NCSA) have a finite ability to achieve high-quality images. The problem stems from a range-dependent (i.e., space-variant) cubic- and higher order terms of range frequency, which require sufficient compensation or space-variant filtering, in the phase of the synthetic aperture radar transfer function, and this letter aims at dealing with this problem. First, an inequation is introduced to evaluate the highest order of range frequency terms whose space-variant coefficient has to be taken into account. Then, based on the method of series reversion, this letter proposes the extended NCS which can weaken the range dependence of the considered range frequency terms and achieve accurate range cell migration correction and range compression. Simulation results are presented to validate the proposed method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • ISAR Imaging via Sparse Probing Frequencies

    Page(s): 451 - 455
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (482 KB) |  | HTML iconHTML  

    Based on compressive sampling theory, a novel method for high-resolution inverse synthetic aperture radar (ISAR) imaging is presented in this letter by transmitting sparse probing frequencies. In this method, only a few measurements in the range frequency and cross-range time domains are needed to reconstruct the target scene by solving an inverse problem through either a linear program or a greedy pursuit. By transmitting merely a few probe frequencies instead of wideband signals, the proposed method can obtain an unambiguous ISAR image with superresolution. The validity of the proposed approach is also confirmed using numerical simulations and real data. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • C-Band Cross-Polarization Wind Speed Retrieval

    Page(s): 456 - 459
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1254 KB) |  | HTML iconHTML  

    C-band ocean backscatter observations over operational weather buoys using RADARSAT-2 fine quad mode data have resulted in new empirical relationships for the C-band co-polarization ratio and the C-band cross-polarization (cross-pol) ocean backscatter. The cross-pol relationship is independent of incidence angle and wind direction, which simplifies wind speed retrieval from synthetic aperture radar imagery for sufficiently high wind speeds. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Automatic Determination of Center of Tropical Cyclone in Satellite-Generated IR Images

    Page(s): 460 - 463
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (250 KB) |  | HTML iconHTML  

    In this letter, a new method is discussed for the automatic determination of the center of tropical cyclones (TCs) by extracting the spiral features within it using the infrared (IR) images from geostationary satellites. Meteosat-5 IR images of two TCs viz., Mala (April 24-29, 2006), and Sub Tropical Storm 4 (STS-4) (October 15-18, 1999) have been analyzed using the image processing techniques, and the center of the TC is then estimated by fitting the spiral at different locations. The present method provides accurate estimates of the cyclone center for the images where the spiral patterns are well featured. However, the method leads to larger errors during formative or decaying phase of cyclone due to the absence of robust pattern in the images. The present method has a potential to be applied in a completely automated mode and can be used to replace the manual center determination which is being done traditionally. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Sensitivity to Foliar Anthocyanin Content of Vegetation Indices Using Green Reflectance

    Page(s): 464 - 468
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (167 KB) |  | HTML iconHTML  

    Anthocyanins are nonphotosynthetic water-soluble pigments associated with the resistance of plants to environmental stresses such as drought, low soil nutrients, high radiation, herbivores, and pathogens. Information on the absolute and relative amounts of anthocyanins allows evaluating the physiological conditions of plants and their responses to stress and has the potential for evaluating plant species diversity across broad geographic regions. As anthocyanins absorb radiation in the green region of the electromagnetic spectrum (with a peak of absorption at around 540-560 nm), broadband vegetation indices that use this spectral region in their formulation will exhibit sensitivity to their presence. In this letter, we evaluate the sensitivity of four broadband vegetation indices using reflectance in the green spectral region to foliar anthocyanin content. Among the indices tested, the visible atmospherically resistant vegetation index was found to be closely and linearly related to the relative amount of foliar anthocyanin across five different species (the root-mean-square error of the prediction is ca. 0.1, and the relative error is below 20%). While this result was obtained at leaf level, it opens new possibilities for analyzing anthocyanin content and composition across multiple scales by means of spacecraft-mounted broadband sensor systems such as Landsat Thematic Mapper, Landsat Enhanced Thematic Mapper Plus, and Moderate Resolution Imaging Spectroradiometer. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Influence of Interference on Range Estimation in Noise Radar Systems

    Page(s): 469 - 473
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (127 KB) |  | HTML iconHTML  

    The problem of false range estimation in noise radars operating in interference environment is investigated. A closed-form expression for the probability of false range estimation when the received signal is corrupted by interference with arbitrary phase is derived, and it contains elementary mathematical functions only. Simulations support the derived probability. The expression can be easily adapted for the case when the interference is not present. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Hybrid Bayesian Classifier for Improved Classification Accuracy

    Page(s): 474 - 477
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (439 KB) |  | HTML iconHTML  

    The widely used Bayesian classifier is based on the assumption of equal prior probabilities for all the classes. However, inclusion of equal prior probabilities may not guarantee high classification accuracy for the individual classes. Here, we propose a novel technique-Hybrid Bayesian Classifier (HBC)-where the class prior probabilities are determined by unmixing a supplemental low spatial-high spectral resolution multispectral (MS) data that are assigned to every pixel in a high spatial-low spectral resolution MS data in Bayesian classification. This is demonstrated with two separate experiments-first, class abundances are estimated per pixel by unmixing Moderate Resolution Imaging Spectroradiometer data to be used as prior probabilities, while posterior probabilities are determined from the training data obtained from ground. These have been used for classifying the Indian Remote Sensing Satellite LISS-III MS data through Bayesian classifier. In the second experiment, abundances obtained by unmixing Landsat Enhanced Thematic Mapper Plus are used as priors, and posterior probabilities are determined from the ground data to classify IKONOS MS images through Bayesian classifier. The results indicated that HBC systematically exploited the information from two image sources, improving the overall accuracy of LISS-III MS classification by 6% and IKONOS MS classification by 9%. Inclusion of prior probabilities increased the average producer's and user's accuracies by 5.5% and 6.5% in case of LISS-III MS with six classes and 12.5% and 5.4% in IKONOS MS for five classes considered. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Radar Retrieval of Surface and Deep Soil Moisture and Effect of Moisture Profile on Inversion Accuracy

    Page(s): 478 - 482
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (198 KB) |  | HTML iconHTML  

    We study the retrieval of surface and deep moisture of bare soil from noisy radar observations using simulated annealing. Due to moisture variations with depth, we model bare soil with a stratified dielectric profile with a rough surface on top. Small perturbation method (SPM) is used as the forward model. We use the full moisture profile for radar data synthesis and study the retrieval accuracy by varying the number of layers that represent the soil profile during inversion. The effect of measurement frequency on the accuracy of deep moisture retrieval is investigated. This work is intended for assessing the effect of subsurface profile on soil moisture retrieval from radar observations of NASA's Soil Moisture Active and Passive (SMAP) mission and future lower frequency airborne or spaceborne systems that may follow SMAP. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • SODAR Pattern Classification by Graph Matching

    Page(s): 483 - 487
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (737 KB) |  | HTML iconHTML  

    The sound detection and ranging (SODAR) system is an effective and active remote sensing tool to probe, in round-the-clock basis, the lower planetary boundary layer (LPBL) of the earth. The observations obtained from such SODAR systems can prove to be extremely useful for LPBL studies if classified and interpreted automatically. Manual interpretation of such data by an expert in this field is very tedious and error-prone. Hence, in this letter, we attempt to classify such data obtained from monostatic SODAR system, which is represented as echogram, by graph matching method. We initially convert the time domain's sample intensity variation, which is recorded as height versus time scale on echogram, to frequency domain for obtaining higher discriminating power of each sample of each class (as for example, thermal plume, inversion, etc.) of the echogram. For discriminating the individual class of the echogram, we use a measure of similarity. Thus, an expert system using graph matching method based on the frequency domain representation of each SODAR sample of each class is developed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Label Alteration to Improve Underwater Mine Classification

    Page(s): 488 - 492
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (257 KB) |  | HTML iconHTML  

    A new algorithm for performing supervised classification that intentionally alters the training labels supplied with the data set is presented. The proposed approach is motivated by the insight that the average prediction of a group of sufficiently informed people is often more accurate than the prediction of any one supposed expert. This idea that the “wisdom of crowds” can outperform a single expert is implemented in two ways. When labeling error rates can be estimated, sets of labels are drawn as samples from a Bernoulli distribution. When side information is not available, or no labeling errors are suspected, labels are intentionally altered in a structured manner. The framework is demonstrated in the context of an underwater mine classification application on synthetic aperture sonar data collected at sea, with promising results. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Short-Time Fourier Transform of Deeply Located Tunnel Signatures Measured by Cross-Borehole Pulse Radar

    Page(s): 493 - 496
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (603 KB) |  | HTML iconHTML  

    The pulse signatures of a deeply located dormant tunnel are measured by operating cross-borehole short-pulse radar in a well-suited tunnel test site in Korea. The relatively fast arrival of the first peak at depth of the empty tunnel, as indicated by data analysis, may play a key role in detecting the tunnel's precise location. Following short-time Fourier transform (STFT) of the data, the arrival time of the first peak is shown to be faster and more distinctive than that without STFTThe pulse signatures of a deeply located dormant tunnel are measured by operating cross-borehole short-pulse radar in a well-suited tunnel test site in Korea. The relatively fast arrival of the first peak at depth of the empty tunnel, as indicated by data analysis, may play a key role in detecting the tunnel's precise location. Following short-time Fourier transform (STFT) of the data, the arrival time of the first peak is shown to be faster and more distinctive than that without STFT if the observation frequency is properly selected. if the observation frequency is properly selected. View full abstract»

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

Aims & Scope

IEEE Geoscience and Remote Sensing Letters (GRSL) is a monthly publication for short papers (maximum length 5 pages) addressing new ideas and formative concepts in remote sensing as well as important new and timely results and concepts.

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Alejandro C. Frery
Universidade Federal de Alagoas