A compound representation of high resolution sea clutter
01 Sep 1980-Vol. 82, pp 21492
TL;DR: In this article, a form of compound distribution is proposed to describe the non-Rayleigh distribution and correlation properties of high-resolution radar sea clutter and a possible physical mechanism is discussed.
Abstract: A proposed form of compound distribution to describe the non-Rayleigh distribution and correlation properties of high resolution radar sea clutter is shown to be a good fit to experimental data. From this model the K distribution is derived, and a possible physical mechanism is discussed.
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01 Jan 1999
TL;DR: In this article, the authors investigated whether or not nonlinear predictor networks can be used to improve the performance of high-resolution surveillance radars which are used to detect targets on, or near the sea surface.
Abstract: This work deals with investigating whether or not nonlinear predictor networks can be used to improve the performance of high resolution surveillance radars which are used to detect targets on, or near the sea surface. Prediction and detection results are presented for new sea clutter data sets.
15 citations
Dissertation•
18 Dec 2012
TL;DR: In this paper, a radar FMCW aeroporte de detection of obstacles fonctionnant en bande X is presented. But the main object of this work is to evaluate the performance of the radar's ability to detect obstacles.
Abstract: Cette these, realisee en partenariat avec Rockwell-Collins France, s'inscrit dans le cadre du developpement d'un radar FMCW aeroporte de detection d'obstacles fonctionnant en bande X. Dans cette these, nous nous placons dans le contexte plus general de detection de cibles presentant un risque de collision avec le porteur radar dans du fouillis de sol. Les performances de detection des cibles d'interet diminuent grandement lorsqu'elles se retrouvent dans les zones de fouillis. Le principal objectif de cette these reside ainsi dans la conception de traitements en vue d'ameliorer les capacites de detection et de reconnaissance de cibles presentant un risque de collision avec le porteur radar dans les zones de fouillis de sol. Dans un premier temps, nous effectuons une revue des traitements adaptes a la detection d'obstacles par un radar aeroporte FMCW: formation de faisceaux conventionnelle, compensation de migration distance, et creation d'une cartographie distance-vitesse par double FFT. Dans un second temps, nous utilisons ensuite un traitement d'antennes adaptatif pour separer en elevation le fouillis de sol et d'eventuels obstacles situes au-dessus du sol pouvant presenter un risque pour le porteur (câbles, pylones, immeubles, ...). Dans la seconde partie de cette these, nous incluons une information supplementaire sur le signal temporel d'une case distance avec un temps d'integration plus long~: la variation de frequence Doppler des cibles. Une cible de collision ou un câble ne changent pas de frequence tandis qu'un element au sol aura une variation connue dependant de la vitesse du porteur et de son angle de vue. Cette information nous a tout d'abord permis de separer le signal d'un pylone et d'un câble, pour ensuite separer la cible de collision du fouillis de sol. Enfin, nous effectuons la detection adaptative d'une cible mobile de collision etendue en distance et noyee dans le fouillis de sol. Les algorithmes developpes dans cette these ont ete testes avec succes sur donnees experimentales.
13 citations
Cites background from "A compound representation of high r..."
...Ward [100] retrouve cette loi K en étudiant le fouillis de mer sur données réelles et en donne une interprétation à deux échelles....
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Dissertation•
01 Jan 2010
TL;DR: La faisabilite de la detection du sillage de navires en imagerie radar, eventuellement bistatique, afin d’obtenir des parametres tels que le cap et the vitesse du navire, est dediee a l’etude de la detectabilite du sillages adapte stochastique.
Abstract: Nous etudions la faisabilite de la detection du sillage de navires en imagerie radar, eventuellement bistatique, afin d’obtenir des parametres tels que le cap et la vitesse du navire. Dans un premier temps, on decrit la chaine d’acquisition radar bistatique ainsi que l’environnement maritime, en particulier les modeles de diffusion sur la surface rugueuse et la maniere d’obtenir une carte des hauteurs des vagues de sillage de Kelvin d’un navire. On decrit ensuite un simulateur de signaux radars bruts en configuration bistatique, en validant les resultats obtenus avec des donnees radar monostatiques disponibles dans la litterature. La seconde partie de la these est dediee a l’etude de la detectabilite du sillage de navires. On traite tout d’abord du cas de la detection du sillage d’eau morte, en realisant un test comparatif de quatre chaines de reference representatives. On traite ensuite la detectabilite du sillage de Kelvin dans des images radar de haute resolution, en commencant par discuter le choix d’une configuration radar optimisant la visibilite du sillage, puis en presentant un algorithme de detection et de traitement base sur la theorie du filtrage adapte stochastique. Cet algorithme fonctionne egalement sur des donnees d’imagerie spatiale optiques haute resolution.
8 citations
Cites background from "A compound representation of high r..."
...Les modèles traditionnels de bruit de chatoiement dans les images radar marines comptent traditionnellement la distribution de Rayleigh, la distribution de Weibull et la distribution K [192] ; on trouvera un bon passage en revue de ces modèles dans l’ouvrage de référence de Ward, Tough et Watts [194], ainsi que dans [6] et [56]....
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TL;DR: In this paper, the problem of detecting a marine target with coherent radars in a correlated heavy-tailed sea clutter background is solved by using the maximum a posterior estimate of the clutter texture and constrained approximate maximum likelihood estimator of the speckle covariance matrix.
Abstract: This article deals with the problem of detecting a marine target with coherent radars in a correlated heavy-tailed sea clutter background. The heavy-tailed sea clutter is modeled by a compound-Gaussian model, and the clutter texture is characterized by the lognormal distribution with a new parameterization form. We develop an adaptive coherent detector on the basis of the two-step generalized likelihood ratio test. The proposed detector can achieve adaptation to sea clutter characteristics by using the maximum a posterior estimate of the clutter texture, the constrained approximate maximum likelihood estimator of the speckle covariance matrix, and the proposed negative- and positive-fractional moment estimate of amplitude parameters of sea clutter. Remarkably, the proposed detector inherently ensures a constant false alarm rate with respect to the clutter power mean and the speckle covariance matrix. Finally, numerical experiments using simulated data and real radar data demonstrate that the proposed estimator and adaptive coherent detector outperform their respective competitors.
7 citations
27 Aug 2016
TL;DR: The MATE-CFAR 2.0 modelo as discussed by the authors is reconocible as the mejor modelo for clutter marino, i.e., it is the modelo that is the most similar to ours.
Abstract: El clutter marino es una senal interferente que aparece en los sistemas de radar que operan en escenarios oceanicos o costeros. Los autores modelaron en MATLAB la distribucion K, ampliamente reconocida como el mejor modelo para clutter marino ya que tiene en cuenta los dos mecanismos de fluctuacion presentes en la senal de fondo. La implementacion permite un acceso facil a la manipulacion de las funciones de distribucion de probabilidad, funciones generadoras, momentos, algoritmos de bondad de ajuste y estimacion de parametros de la distribucion. Expresiones matematicas y notaciones de funciones informaticas fueron definidas para contribuir a la unificacion de los estudios de clutter de radar relacionados al modelo K. La solucion es un punto de partida para el desarrollo de nuevos esquemas de deteccion por parte del grupo de investigacion de radares de la Facultad de Electrica de la CUJAE y contribuye a la conformacion de la libreria MATE-CFAR 2.
7 citations
References
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TL;DR: In this paper, a mathematical model for non-Rayleigh microwave sea echo is developed which describes explicitly the dependence of statistical properties of the radar cross section on the area of sea surface illuminated by the radar.
Abstract: A mathematical model for non-Rayleigh microwave sea echo is developed which describes explicitly the dependence of statistical properties of the radar cross section on the area of sea surface illuminated by the radar. In addition to the first probability distribution of the scattered radiation, its temporal and spatial correlation functions are also considered. It is shown that, in general, these correlation functions decay on at least two scales, the second, non-Rayleigh, contributions being strongly dependent on the properties of a "single scatterer." Predictions of the model are found to be in qualitative agreement with existing experimental data. A new class of probability distributions, the " K -distributions," is introduced, which may prove useful for fitting such data.
896 citations
Book•
01 Jan 2006
TL;DR: In this paper, the authors present an authoritative account of the current understanding of radar sea clutter, including the characteristics of radar clutter, modelling radar scattering by the ocean surface, statistical models of sea clutter and other random processes, detection of small targets in sea clutter.
Abstract: Sea Clutter: Scattering, the K Distribution and Radar Performance, 2nd Edition gives an authoritative account of our current understanding of radar sea clutter. Topics covered include the characteristics of radar sea clutter, modelling radar scattering by the ocean surface, statistical models of sea clutter, the simulation of clutter and other random processes, detection of small targets in sea clutter, imaging ocean surface features, radar detection performance calculations, CFAR detection, and the specification and measurement of radar performance. The calculation of the performance of practical radar systems is presented in sufficient detail for the reader to be able to tackle related problems with confidence. In this second edition the contents have been fully updated and reorganised to give better access to the different types of material in the book. Extensive new material has been added on the Doppler characteristics of sea clutter and detection processing; bistatic sea clutter measurements; electromagnetic scattering theory of littoral sea clutter and bistatic sea clutter; the use of models for predicting radar performance; and use of the K distribution in other fields.
606 citations
TL;DR: A new similarity measure for automatic change detection in multitemporal synthetic aperture radar images based on the evolution of the local statistics of the image between two dates, which allows a multiscale approach in the change detection for operational use.
Abstract: In this paper, we present a new similarity measure for automatic change detection in multitemporal synthetic aperture radar images. This measure is based on the evolution of the local statistics of the image between two dates. The local statistics are estimated by using a cumulant-based series expansion, which approximates probability density functions in the neighborhood of each pixel in the image. The degree of evolution of the local statistics is measured using the Kullback-Leibler divergence. An analytical expression for this detector is given, allowing a simple computation which depends on the four first statistical moments of the pixels inside the analysis window only. The proposed change indicator is compared to the classical mean ratio detector and also to other model-based approaches. Tests on the simulated and real data show that our detector outperforms all the others. The fast computation of the proposed detector allows a multiscale approach in the change detection for operational use. The so-called multiscale change profile (MCP) is introduced to yield change information on a wide range of scales and to better characterize the appropriate scale. Two simple yet useful examples of applications show that the MCP allows the design of change indicators, which provide better results than a monoscale analysis
500 citations
TL;DR: In this article, the generalized K model with a non-uniform distribution of phase by a fluctuating population of objects is derived on the bases of simpler and more general arguments.
Abstract: The generalized K distribution, introduced recently by Barakat [ J. Opt. Soc. Am. A3, 401 ( 1986)] as a model for the intensity of radiation scattered with a nonuniform distribution of phase by a fluctuating population of objects, is derived on the bases of simpler and more general arguments. In particular, Barakat’s analysis is based on a random walk in two dimensions and a specific model for the phase distribution; our analysis is presented in terms of an n-dimensional walk with a directional bias that, apart from its scaling property as a function of the mean number of scatters, is arbitrary. The relationship of the generalized K model with possible underlying scattering mechanisms is also discussed.
269 citations
TL;DR: In this paper, the problem of detecting radar targets against a background of coherent, correlated, non-Gaussian clutter is studied with a two-step procedure, where in the first step, the structure of the amplitude and the multivariate probability density functions (pdfs) describing the statistical properties of the clutter is derived.
Abstract: The problem of detecting radar targets against a background of coherent, correlated, non-Gaussian clutter is studied with a two-step procedure. In the first step, the structure of the amplitude and the multivariate probability density functions (pdfs) describing the statistical properties of the clutter is derived. The starting point for this derivation is the basic scattering problem, and the statistics are obtained from an extension of the central limit theorem (CLT). This extension leads to modeling the clutter amplitude statistics by a mixture of Rayleigh distributions. The end product of the first step is a multidimensional pdf in the form of a Gaussian mixture, which is then used in step 2. The aim of step 2 is to derive both the optimal and a suboptimal detection structure for detecting radar targets in this type of clutter. Some performance results for the new detection processor are also given. >
255 citations