基于小波变换和马尔可夫随机场的极化SAR图像自动分类

本文提出一种对极化合成孔径雷达(SAR)图像进行自动多分辨率分类的方法。首先利用多视极化白化滤波(MPWF)抑制极化SAR图像的相干斑,得到反映地物辐射特征的纹理SAR图像,然后利用小波变换(WT)提取不同分辨率的纹理信息,在最低分辨率级利用Akaik信息准则(AIC)自动估计图像中的纹理类数,进而在各个分辨率级利用马尔可夫随机场(MRF)模型表征各像素间的空间关联信息,并分别利用最大似然(ML)方法和循环条件模式(ICM)进行自动的模型参数估计和最大后验概率(MAP)分类,最后应用NASA/JPL机载L波段极化SAR数据验证了本文所提分类方法的有效性和优越性。     

基于H-α和改进C-均值的全极化SAR图像非监督分类

该文提出一种基于H-α和改进C-均值的全极化SAR图像非监督分类方法.该方法先按H-α对全极化SAR图像进行基于散射机理的分类,再将分类结果作为改进C-均值算法的初始类别划分,从而实现地物分类.迭代次数确定是C-均值动态聚类算法的关键,文中利用图像熵给出了一种新的迭代终止准则.与H-α方法相比,该文方法能在保留分类结果物理散射机理的同时,实现有效的地物分类.NASA/JPL实验室AIRSAR系统获取的L波段旧金山全极化SAR数据的实验结果验证了该文方法的有效性.     

High-resolution change estimation of soil moisture using L-band radiometer and Radar observations made during the SMEX02 experiments

The soil moisture experiments held during June-July 2002 (SMEX02) at Iowa demonstrated the potential of the L-band radiometer (PALS) in estimation of near surface soil moisture under dense vegetation canopy conditions. The L-band radar was also shown to be sensitive to near surface soil moisture. However, the spatial resolution of a typical satellite L-band radiometer is of the order of tens of kilometers, which is not sufficient to serve the full range of science needs for land surface hydrology and weather modeling applications. Disaggregation schemes for deriving subpixel estimates of soil moisture from radiometer data using higher resolution radar observations may provide the means for making available global soil moisture observations at a much finer scale. This paper presents a simple approach for estimation of change in soil moisture at a higher (radar) spatial resolution by combining L-band copolarized radar backscattering coefficients and L-band radiometric brightness temperatures. Sensitivity of AIRSAR L-band copolarized channels has been demonstrated by comparison with in situ soil moisture measurements as well as PALS brightness temperatures. The change estimation algorithm has been applied to coincident PALS and AIRSAR datasets acquired during the SMEX02 campaign. Using AIRSAR data aggregated to a 100-m resolution, PALS radiometer estimates of soil moisture change at a 400-m resolution have been disaggregated to 100-m resolution. The effect of surface roughness variability on the change estimation algorithm has been explained using integral equation model (IEM) simulations. A simulation experiment using synthetic data has been performed to analyze the performance of the algorithm over a region undergoing gradual wetting and dry down.     

Radar Observation Over Freiburg

The SIR-B experiment over the German test siteei-Freiburg/Kaiserstuhl documents the usefulness of L-band radar data for land use classification. It shows furthermore the importance of the spatial resolution for target signature analyses and demonstrates the usefulness of compact receivers and active calibrators for sensor calibration.     

一种多视极化SAR广义K-分布的研究

本文提出一种极化合成孔径雷达(SAR)广义K-分布模型用于描述经多视处理的、高分辨率的全极化SAR成像数据的统计特性,其特点是各极化通道的纹理为部分相关的gamma分布.利用纹理与相干斑乘性模型,首先导出了部分相关纹理的联合概率密度函数和多视广义极化SARK-分布概率密度函数;然后给出了基于联合矩的分布参数估计方法;最后利用真实SAR数据进行了模型的试验.     

多视极化SAR图象相干斑抑制的研究

本文研究多视极化合成孔径雷达(SAR)图象的相干斑抑制,提出多视极化白化滤波(MPWF)法,并进一步将它发展成具有多通道输出的全极化滤波器。本文还定量地分析了MPWF方法抑制相干斑的能力,并在理论上同全功率法、加权法和功率均衡法进行了比较。应用NASA/JPL机载L波段四视全极化SAR数据的试验结果验证了所提方法的有效性和优越性,也说明了MPWF处理能显著地提高SAR图象的分类精度。     

多视极化合成孔径雷达图象的分类和极化通道优化

本文提出一个新的最大似然(ML)分类算法对多视全极化合成孔径雷达(SAR)图象进行分类,给出了应用NASA/JPL机载L波段四视全极化SAR实测数据的试验结果,证明了新算法的有效性。此外,本文还将所提算法应用于部分的多视全极化SAR数据中,实现了地貌类型分类的极化通道优化。     

CLASSIFICATION OF MULTI-LOOK POLARIMETRIC SAR IMAGERY AND POLARIZATION CHANNEL OPTIMIZATION

In this paper, a new maximum likelihood (ML) classification algorithm is proposed to classify the multi-look polarimetric synthetic aperture radar (SAR) imagery. Experimental results with the NASA/JPL airborne L-band polarimetric SAR data demonstrate the effectiveness of the new algorithm. Furthermore, when using the algorithm in the classifications with subsets of the multi-look polarimetric SAR data, the polarization-channel optimization for the terrain type classification is implemented.     

一种基于极化圆周SAR图像的陆上桥梁提取方法

桥梁作为重要的人造目标,一直都是合成孔径雷达(SAR)图像解译的重要对象之一.目前针对桥梁检测问题已开展了较多研究,核心思想是:首先提取出河流水体,然后再根据河流与桥梁的位置关系检测桥梁.然而,已有的桥梁检测方法依赖于河流提取,很难实现陆上桥梁检测.因为陆上桥梁下方的背景不再是河流,而是陆地,其散射特性、形状分布与河流...     

Calibration of linearly polarized polarimetric SAR data subject to Faraday rotation

A model for linearly polarized fully polarimetric backscatter measurements is used, incorporating the effects of system noise, channel amplitude, phase imbalance, crosstalk, and Faraday rotation. A step-by-step procedure is outlined for correction (or calibration) of fully polarimetric data subject to Faraday rotation, to recover the true scattering matrix. The procedure identifies steps for crosstalk removal and correction of channel imbalances that are robust in the presence of Faraday rotation. The final steps in the procedure involve a novel strategy for estimation and correction of Faraday rotation. Three approaches to estimate the (one-way) Faraday rotation angle /spl Omega/ directly from linear (quad-) polarized synthetic aperture radar (SAR) backscatter data obtained by a spaceborne SAR system are described. Each approach can initially be applied to the signature of any scatterer within the scene. Sensitivity analyses are presented that show that at least one of the measures can be used to estimate /spl Omega/ to within /spl plusmn/3/spl deg/ to 5/spl deg/, with reasonable levels of residual crosstalk, noise floor, channel amplitude, and phase imbalance. Ambiguities may be present in the estimates of /spl Omega/ of /spl plusmn/n/spl pi//2 - the impact of this is discussed, and several approaches are suggested to deal with this possibility. The approach described in this paper is relevant for future L-band spaceborne SARs and removes one key obstacle to the deployment of even longer wavelength SARs (e.g., an ultrahigh frequency or P-band SAR) in Earth orbit.     

多极化SAR图像的降斑研究

对于多极化SAR图像,可以利用其同极化和交叉极化图像的相关性来进行降斑处理.本文对常用的几种基于多极化SAR图像的降斑方法进行了分析,重点研究了最优加权法(the optimal weighting algorithm),在其基础上改进提出了分块加权法,取得了明显的降斑效果,并较大地减少了运算量.最后利用实测的SAR数据进行了验证.     

Sea Ice Deformation State From Synthetic Aperture Radar Imagery—Part II: Effects of Spatial Resolution and Noise Level

C- and L-band airborne synthetic aperture radar (SAR) imagery acquired at like- and cross-polarizations over sea ice under winter conditions is examined with the objective to study the discrimination between level ice and ice deformation features. High-resolution low-noise data were analyzed in the first paper. In this second paper, the main topics are the effects of spatial resolution and signal-to-noise ratio. Airborne high-resolution SAR scenes are used to generate a sequence of images with increasingly coarser spatial resolution from 5 to 25 m, keeping the number of looks constant. The signal-to-noise ratio is varied between typical noise levels for airborne imagery and satellite data. Areal fraction of deformed ice and average deformation distance are determined for each image product. At L-band, the retrieved values of the areal fraction get larger as the image resolution is degraded. The areal fraction at C-band remains constant. The retrieved average distance between deformation features increases both at C- and L-bands as the image resolution gets coarser. The influence of noise becomes noticeable if its level is equal or larger than the average intensity backscattered from the level ice. The retrieval of deformation parameters using simulated images that resemble ERS-2 SAR, Envisat ASAR, and ALOS PALSAR data products is discussed. Basic differences between real and simulated ERS-2 SAR images are analyzed.      

SVM全极化SAR图像分类中的特征选择

本文将SVM用于全极化SAR图像分类,并提出一种新的应用于SVM分类的特征选择算法。该算法以支持向量个数作为特征评估准则,利用顺序前进法加入特征。基于NASA/JPL实验室AIRSAR系统的L波段荷兰Flevoland全极化数据的与RELIEF-F算法的对比实验表明,在特征个数更少(或相当)的情况下,本文特征选择算法能在更广泛的SVM参数取值范围内获得更高的分类精度。     

在振动环境下相位噪声对星机BiSAR的影响

振荡器的相位噪声是影响BiSAR获得高分辨率图像的重要因素之一。振荡器是一种对振动极为敏感的器件。因此,在振动环境下,定量分析相位噪声对BiSAR的影响是十分必要的。文中基于两个独立非同分布的振荡器,机载SAR在静态条件和随机振动环境下,推导了星载一机栽混合BiSAR（SA-BiSAR）积分旁瓣比的计算公式。仿真结果表明,在静态条件下,SA—BiSAR仍然具有很低的相噪谱;机载SAR在振动环境下,对于L波段,可以满足成像的基本要求;对于X波段,需采取必要的隔振措施提高系统的抗振性能来满足成像的条件。     

Signal subspace change detection in averaged multilook SAR imagery

This paper addresses change detection in averaged multilook synthetic aperture radar (SAR) imagery. Averaged multilook SAR images are preferable to full-aperture SAR reconstructions when the imaging algorithm is approximation-based (e.g., polar format processing) or when motion data are not accurate over a long full aperture. We examine the application of a SAR change-detection method, known as signal subspace processing, which is based on the principles of two-dimensional adaptive filtering, and we use it to recognize the addition of surface landmines to a particular area under surveillance. We describe the change-detection problem as a trinary hypothesis testing problem, and define a change signal and its normalized version to determine whether: 1) there is no change in the imaged scene; 2) a target has entered the imaged scene; or 3) a target has exited the imaged scene. A statistical analysis of the error signal is provided to show its properties and merits. Results are presented for averaged noncoherent multilook and coherent single-look X-band SAR imagery.     

Contributions to Oil-Spill Detection and Analysis with Radar and Microwave Radiometry: Results of the Archimedes II Campaign

During the Archimedes II campaign in November 1985 (conducted and sponsored by JRC ISPRA) different DFVLR-instruments were flown, an X-band SLAR, an elementary L-band SAR, and microwaveradiometers at 32 and 90 GHz. The objective of these measurements was to evaluate the possibility of detection, localization, and qualification of oil pollution with microwave sensors. Examples of measurement results obtained are presented. As a main result, it can be stated that all of these microwave instruments are valuable and necessary tools for oil pollution detection andoil collection systems.     

基于支持向量机的极化SAR图像分类

与传统最大似然（ML）分类器相比，支持向量机（SVM）在小训练样本时仍具有良好的分类性能，目前已广泛应用于多个领域。该文在极化SAR特征提取的基础上，将SVM应用于极化SAR图像分类，分析了分类器参数对分类性能的影响。利用NASA／JPL实验室AIRSAR系统的L波段旧金山全极化SAR数据比较了SVM和ML的分类性能，并进一步给出了基于SVM的国内某地区双极化SAR图像分类结果。     

Estimation of the Minimum Number of Tracks for SAR Tomography

Synthetic aperture radar tomography (SARTom) is the natural extension of SAR interferometry to solve for multiple phase centers within a resolution cell and obtain the 3-D representation of a scene. This paper deals with the determination of the minimum number of tracks required to perform SARTom. Through the prolate spheroidal wave functions, the number of equivalent targets of a volumetric source is derived, and from it, the minimum number of observations required to apply subspace superresolution methods is computed. The minimum tomographic aperture length is also investigated. The results are validated on real data acquired in L-band by the experimental SAR system of the German Aerospace Center.      

Polarization of light scattered by vegetation

The potential information in polarization data of both single leaves and plant canopies is investigated. Measurements demonstrate the relationship between polarization data and various optical and botanical properties of both pieces of foliage and plant canopies. The results provide a basis for gaining fundamental understanding of how light is scattered and polarized by a plant canopy. The results show the polarized and nonpolarized portions of the light scattered by a remotely sensed ground scene potentially are independent sources of information for discriminating species and assessing the condition of plant canopies.     

基于分形特征的高分辨率SAR图像分类

通过大量的实验，研究了3种分形特征提取算法在高分辨率SAR图像分类中的适应情况和彼此的差异性。对分形特征提取的图像量化等级、窗口大小、点对数的确定以及坏值剔除数量进行了深入的研究。在此基础上，总结了适合高分辨率SAR图像地物分类的分形特征提取的一般规律。最后，提出了利用分形特征的统计量作为特征向量，运用模糊C均值算法对图像进行分类，并取得了很好的效果。