一种基于Bayesian准则和MRF模型的SAR图像滤波方法

提出了一种新的斑点噪声的滤波方法,该方法基于小波分解的框架,采用小波域隐MRF模型,计算图像中表征像素纹理特征的隐状态参数的后验概率,以此后验概率作为权重因子对传统GammaMAP滤波算法进行改进。该算法被用于模拟SAR图像和真实ERS 1图像的Speckle抑制。试验结果表明,与传统Gam maMAP算法相比,本文提出的方法能更好地抑制Speckle,并保持图像细节。     

SAR图像多尺度积增强的目标检测算法

合成孔径雷达（SAR）成像系统的热噪声和海杂波严重影响SAR图像自动目标检测的性能,去噪和均匀背景杂波是提高SAR图像目标检测性能的重要课题。根据SAR图像噪声功率一般存在于信号小尺度,没有跨尺度特征,而目标信号的边缘具有跨尺度的特点,本文提出了一种多尺度积信号增强和去噪的SAR图像船舰目标检测算法。本算法对SAR图像进行小波变换,应用多尺度积在小波域增强SAR图像船舰信号和均匀背景杂波,再对SAR图像进行目标检测。ERS SAR图像用于验证本文算法。仿真实验结果表明,新算法同传统的双参数CFAR检测算法、基于K-分布背景杂波的检测算法以及基于小波软阈值增强的检测算法相比,在虚警数和品质因数性能指标上均优于后几种检测算法。     

Reproduction of temporal scaling by a rectangular pulses rainfall model

The presence of scaling statistical properties in temporal rainfall has been well established in many empirical investigations during the latest decade. These properties have more and more come to be regarded as a fundamental feature of the rainfall process. How to best use the scaling properties for applied modelling remains to be assessed, however, particularly in the case of continuous rainfall time‐series. One therefore is forced to use conventional time‐series modelling, e.g. based on point process theory, which does not explicitly take scaling into account. In light of this, there is a need to investigate the degree to which point‐process models are able to ‘unintentionally’ reproduce the empirical scaling properties. In the present study, four 25‐year series of 20‐min rainfall intensities observed in Arno River basin, Italy, were investigated. A Neyman–Scott rectangular pulses (NSRP) model was fitted to these series, so enabling the generation of synthetic time‐series suitable for investigation. A multifractal scaling behaviour was found to characterize the raw data within a range of time‐scales between approximately 20 min and 1 week. The main features of this behaviour were surprisingly well reproduced in the simulated data, although some differences were observed, particularly at small scales below the typical duration of a rain cell. This suggests the possibility of a combined use of the NSRP model and a scaling approach, in order to extend the NSRP range of applicability for simulation purposes. Copyright © 2002 John Wiley & Sons, Ltd.     

Rating health and stability of engineering structures via classification indexes of InSAR Persistent Scatterers

We propose a novel set of indexes to classify the information content of Persistent Scatterers (PS) and rate the health of engineering structures at urban to local scale. PS are automatically sampled and grouped via ‘control areas’ coinciding with the building and its surrounding environment. Density over the ‘control areas’ and velocity of PS are converted respectively into: Completeness of Information Index (I_ci) that reflects the PS coverage grade; and Conservation Criticality Indexes (I_cc) which rate the health condition of the monument separately for the object and surrounding control areas. The deformation pattern over the structure is classified as isolated (i) or diffused (d) based on the Velocity Distribution Index (I_vd). Both I_ci and I_cc are rated from A to E classes using a colour-coded system that intentionally emulates an energy-efficiency scale, to encourage the exploitation of PS by stakeholders and end-users in the practise of engineering surveying. Workability and reliability of the classification indexes are demonstrated over the urban heritage of Florence, Italy, using well established ERS-1/2 (1992–2000) descending, ENVISAT (2003–2010) ascending and descending PS datasets. The indexes are designed in perspective of handling outputs from InSAR processing of higher-resolution time series.     

矩形箱涵拉顶式施工中掘进机头拉力的计算

系统地介绍了矩形箱涵拉顶式施工中,掘进机头轴线方向的倾侧纠偏、机头顶进间歇防回缩所需的拉力的计算方法,并通过工程实例印证。根据理论分析和相应的计算公式可以得出矩形箱涵采用＂拉顶式＂工艺施工时,在其接受井内配置的拉力较为精确的计算结果,并能满足实际工程的需要。     

弹性波法检测大孔径爆破对基岩松驰层厚度影响的探讨

根据大孔径梯段爆破开挖对底部基岩扰动影响的声波检测情况,对检测资料进行了分析研究,给出了大孔径开挖底部基岩预留保护层厚度,供工程参考。     

大地坐标系与投影坐标系

在物探化探工作中,所有的测点在陆地、海洋、空中均有它唯一的空间位置。在工作的不同阶段,测点位置按工作设计要求采用不同的方式予以标示。在实地观测时,测点定位采用全球定位系统GPS（DGPS）,由大地坐标系的大地坐标标示测点位置。在展示工作成果时,则采用投影坐标系的平面直角坐标标示测点位置。这里介绍了大地坐标系、常用投影坐标系的建立与特征,投影坐标系的选择与应用,不涉及具体的计算公式。     

盐丘构造成像速度建模及逆时偏移关键参数优选

针对盐下构造,建立合适的速度模型分析流程是实现逆时偏移高精度成像的前提,选择合理的逆时偏移参数是改善成像效果的关键问题。笔者将单一沿层速度建模方法作了相应改进和调整,采用三步法进行速度建模,提高了盐丘内的速度分析精度,盐丘翼部形态得到了较好的表达。利用三步法的建模结果作 RTM 偏移成像试验,消除了盐下出现的假构造,使盐下小幅度构造背斜细节得到准确成像,实现了对盐丘边界及盐丘侧翼的准确归位。模型试验证明,三步法建模方法适用于复杂盐丘构造的速度建模。同时,在建模精度提高的基础上,针对逆时偏移流程中的子波主频、偏移孔径以及偏移网格关键参数作了分析研究,通过西非地区的实际资料试验,对比成像结果的质量,优化参数,消除了由于参数选取不合理而造成的陡倾角成像不准、信噪比降低、数值频散、浪费计算资源等问题的影响,实现了复杂盐丘构造的高精度成像。     

大口径闪烁仪及其在地表能量平衡监测中的应用

介绍了LAS仪器的测量原理及数据处理方法, 并利用中荷合作项目CEWBMS中获得的河南郑州LAS测站2000年的观测资料, 同时结合其它辅助资料, 对观测点附近地区的能量平衡状况进行了分析。分析结果表明, 由LAS测值得到的显热通量值, 以及结合净辐射资料间接得到的潜热通量值, 合理地反映出了当地能量平衡状况的季节变化, 显示出一年之中当地大部分的净辐射能用于潜热通量的释放。其数据结果所表征的当地下垫面干湿程度的变化与同期的降水及土壤相对湿度相比, 表现出了相当好的一致性, 这为拓展LAS在局地地表能量平衡监测中的应用提供了物理依据。     

一种新的INSAR干涉条纹图滤波方法

干涉条纹图滤波是合成孔径雷达干涉测量处理中不可缺少的重要环节.对干涉条纹图滤波的一个重要要求是在有效抑制噪声的同时尽可能地保持条纹的跳变纹理信息.在分析干涉条纹图一阶差分的分布性质和三种当前最常用干涉条纹图滤波的算法的优缺点的基础上,提出基于椭圆方程的干涉条纹方向检测方法,并基于此推导了基于误差方程的用于表述不同方向的像素与滤波窗口中心像素的相关关系的加权模型,以此加权模型修正窗口均值滤波和圆周期均值滤波,得到新的保边缘的滤波器.接着分析了新滤波器的计算复杂度和不同权函数对滤波结果的影响.以此新的椭圆加权的保边缘滤波器处理了河北尚义地区的ERS-1/2合成孔径雷达数据,证明了本文提出的新滤波算法具有噪声抑制效果好,边缘信息保持能力强,计算速度快和可灵活配置等优点.