The Stability of UWB Low-Frequency SAR Images

Abstract

This is the published version of a paper published in IEEE Geoscience and Remote Sensing Letters. Citation for the original published paper (version of record):Renato, M. (2016) The stability of UWB low-frequency SAR images. Letters, 13(8) Access to the published version may require subscription. The statistical analysis based on bivariate distribution data organized into different intervals of magnitude can be an important tool to further understand the properties of the backscattered signal for low-frequency SAR images. In this letter, it is found that, for "good" image pairs, the subtracted image has Gaussian distributed clutter backscattering and that the noise mainly consists of the thermal noise and, therefore, speckle noise does not have to be considered. This is a consequence of the stable backscattering for a UWB low-frequency SAR system. Index Terms-Bivariate distribution, CARABAS-II, clutter, statistical modeling, very high frequency synthetic aperture radar (VHF SAR). IEEE Geoscience and Remote Sensing

RPCA para Detecção de Mudanças em Imagens SAR UWB VHF

“…Dessa forma, considerando que há apenas umaúnica dispersão (scatter) por célula de resolução, e que pequenos objetos são fracamente refletidos, pode-se afirmar que o sistema não será sensívelà rugosidade do solo e ao dossel da floresta, bem como a presença de arbustos, folhas, pequenos galhos, dentre outros objetos de natureza e escala semelhantes. Essa característica torna o ruído decorrente de speckles muito baixo [13], [1]. Em complemento, para sistemas SAR UWB de baixa frequência, as dispersões de 5 metros ou superiores não mudam entre as medições, mesmo para intervalos de tempo de horas ou dias.…”

“…Sabe-se que o radar de abertura sintética (Synthetic Aperture Radar -SAR) de baixa frequência, operando na faixa de frequência VHF (Very High Frequency) e UHF (Ultra High Frequency),é eficiente para a aplicação de detecção de mudanças (Change Detection -CD) [1]. Neste tipo de aplicação, busca-se detectar alterações que ocorram entre diferentes campanhas de medição, realizadas em intervalos de tempo distintos [2].…”

Wavelength-Resolution SAR Incoherent Change Detection Based on Image Stack

“…The statistical analysis about stability of wavelengthresolution SAR images in [6] based on bivariate distribution shows that the subtractions (1), (2) and (3) result into Gaussian distributed clutter. The analysis also shows that the noise mainly consists of the thermal noise and, therefore, it is not necessary to consider speckle noise in wavelength-resolution SAR change detection.…”

Wavelength-Resolution SAR Ground Scene Prediction Based on Image Stack

“…Additionally, small scatterers present in the ground area of interest do not contribute to the backscattering for low-frequency radar systems. Thus, small structures, such as tree branches and leaves, are not shown in SAR images [16]. Because large scatterers are associated with low-frequency components, they tend to be less influenced by environmental effects and are stable in time.…”

“…Wavelength-resolution systems have also shown unique results with high detectability rate on a low false alarm rate per square km, as presented, for example, in [17,24]. The nature of the wavelength-resolution SAR imagery can be exploited to facilitate the design of CDAs, since (i) the contribution of small scatterers to radar echoes is not significant for the wavelength of several meters; (ii) scatter from large objects are the main contribution; (iii) large scatterers are usually stable in time and less sensitive to environmental effects; and (iv) the wavelength-resolution almost totally cancel the speckle noise [16] in the SAR image given a very stable backscattering between measurements.…”