高斯Copula的多光谱遥感影像分割

为了充分利用多光谱影像波段间的相关性,提出高斯Copula的多光谱遥感影像分割方法.首先,建立基于马尔可夫随机场的标号场模型,使用Potts模型刻画该标号场.然后,建立表征像素光谱测度的特征场,利用高斯Copula建立像素光谱测度的多变量统计模型以刻画该特征场.结合标号场、特征场模型及各模型参数的先验概率,利用贝叶斯定理建立多光谱影像分割的后验概率模型.最后,设计适用于模拟后验概率模型的M-H算法,在最大后验概率策略下获取最优分割结果.对模拟和真实多光谱影像分割结果表明,文中方法描述波段间相关性的能力较强,准确性较高.     

遥感异常目标的仿生非线性滤波检测

目的 为了解决复杂背景干扰下基于线性滤波异常检测算法无法有效区分复杂背景特征与异常目标特征,导致检测结果虚警率偏高的问题,提出一种面向复杂背景的遥感异常小目标仿生非线性滤波检测算法。方法 受生物视觉系统利用不同属性信息挖掘高维特征机理的启发,该算法通过相关型非线性滤波器综合多波段光谱数据提取高维光谱变化特征作为异常目标检测检测依据,弥补线性滤波抗噪性能差,难于区分复杂背景特征与目标特征的缺点。结果 仿真实验结果验证该算法在仿真数据及真实遥感数据的异常检测效果上有较大改善,在实现快速异常检测的同时提高了检测命中率。结论 本文方法不涉及背景建模,计算复杂度低,具有较好的实时性与普适性。特别是对复杂背景下的小尺寸异常目标具有较好的检测效果。     

Resolution analysis for Gradient Direction Matching of object model edges to overhead images

The problem of computer-assisted broad area search for specific objects of interest in overhead images is considered. To this end, we present a novel efficient Gradient Direction Matching (GDM) algorithm that matches gradient directions associated with object edges to pixel gradient directions (as opposed to image edges, which are less reliable). GDM seamlessly integrates information associated with pixel location and orientation in such a way that the FFT can be exploited for computational efficiency, and it inherently rejects background clutter. The effects of spatial resolution on GDM statistical performance are studied empirically with the goal of gaining insight into how far GDM computational cost can be reduced before matching performance becomes too severely compromised.     

Multi-channel higher-order local autocorrelation for object detection on satellite images

ABSTRACT

An automatic object-detection method is necessary to facilitate the efficient analysis of satellite images consisting of multispectral images. Considering that the relationship between spectrums is important for discriminating objects in multispectral images. This paper proposes a feature extraction method that can capture both spatial and spectral relationships of the multispectral images. Moreover, image preprocessing and dimensionality reduction procedures are introduced for stable feature extraction. In this study, we conducted experiments for detecting two types of objects by using Landsat 8 images. The proposed method improved the detection performance relative to other image features.     

低分辨率目标的检测与实现

提出以柯西分布作为背景剔除时图像像素比值的统计分布模型,并融合单个像素点和邻近像素点所蕴涵的时空信息,实现了对场景变化自适应的背景图像比值的建模,应用假设检验方法,通过背景剔除(background subtraction)实现了对低分辨率目标具有鲁棒性的检测。最后的实验表明,该文提供的算法可以抗背景中全局或局部光照的渐变和突变,可以有效地抑制背景中活动物体和阴影的杂波干扰,能够适应下雨的恶劣天气。     

The illumination-invariant matching of deterministic localstructure in color images

The availability of multiple spectral measurements at each pixel in an image provides important additional information for recognition. Spectral information is of particular importance for applications where spatial information is limited. Such applications include the recognition of small objects or the recognition of small features on partially occluded objects. We introduce a feature matrix representation for deterministic local structure in color images. Although feature matrices are useful for recognition, this representation depends on the spectral properties of the scene illumination. Using a linear model for surface spectral reflectance with the same number of parameters as the number of color bands, we show that changes in the spectral content of the illumination correspond to linear transformations of the feature matrices, and that image plane rotations correspond to circular shifts of the matrices. From these relationships, we derive an algorithm for the recognition of local surface structure which is invariant to these scene transformations. We demonstrate the algorithm with a series of experiments on images of real objects     

Novel target segmentation and tracking based on fuzzy membership distribution for vision-based target tracking system

One of the basic processes of a vision-based target tracking system is the detection process that separates an object from the background in a given image. A novel target detection technique for suppression of the background clutter is presented that uses a predicted point that is estimated from a tracking filter. For every pixel, the three-dimensional feature that is composed of the x-position, the y-position and the gray level of its position is used for evaluating the membership value that describes the probability of whether the pixel belongs to the target or to the background. These membership values are transformed into the membership level histogram. We suggest an asymmetric Laplacian model for the membership distribution of the background pixel and determine the optimal membership value for detecting the target region using the likelihood criterion. The proposed technique is applied to several infra-red image sequences and CCD image sequences to test segmentation and tracking. The feasibility of the proposed method is verified through comparison of the experimental results with the other techniques.     

A multiscale feature fusion approach for classification of very high resolution satellite imagery based on wavelet transform

A novel methodology based on multiscale spectral and spatial information fusion using wavelet transform is proposed in order to classify very high resolution (VHR) satellite imagery. Conventional wavelet‐based feature extraction methods employ single windows of a fixed size, which are not satisfactory as the VHR imagery contains complex and multiscale objects. In this paper, spectral and spatial features are extracted based on a set of concentric windows around a central pixel in order to integrate the information across different windows/scales. The proposed method is made up of three blocks: (1) the conventional wavelet‐based feature extraction methods are extended from single band processing to multispectral bands, and from single window to multi‐windows, (2) two multiscale fusion algorithms are proposed to exploit the multiscale spectral and spatial information and (3) a support vector machine (SVM), a relatively new method of machine learning, is used to classify the multiscale spectral–spatial feature sets. The proposed classification method is evaluated on two VHR datasets and the results show that the multiscale approach can improve the classification accuracy in homogeneous areas while simultaneously preserving accuracy in edge regions.     

Adaptive determination of filter scales for edge detection

The authors suggest a regularization method for determining scales for edge detection adaptively for each site in the image plane. Specifically, they extend the optimal filter concept of T. Poggio et al. (1984) and the scale-space concept of A. Witkin (1983) to an adaptive scale parameter. To avoid an ill-posed feature synthesis problem, the scheme automatically finds optimal scales adaptively for each pixel before detecting final edge maps. The authors introduce an energy function defined as a functional over continuous scale space. Natural constraints for edge detection are incorporated into the energy function. To obtain a set of optimal scales that can minimize the energy function, a parallel relaxation algorithm is introduced. Experiments for synthetic and natural scenes show the advantages of the algorithm. In particular, it is shown that this system can detect both step and diffuse edges while drastically filtering out the random noise     

基于小波特征和模拟退火的遥感图象快速聚类算法

不同遥感对象，光谱曲线的突变点位置差异很大，不同尺度的小波变换可有效提取这些突变特征，在此基础上，用小波特征相关系数描述像素的近似程度，取代一般聚类算法以欧氏距离为基础的聚类概念，聚类结果可准确反映遥感对象内容，基于小波特征抽取和模拟退火的多光谱遥感图象快速聚类算法，通过扩展频段，增加特征点的个数以丰富类的特性，对空间数据进行均匀抽样产生聚类空间，采用模拟退火技术和逐步降低聚类规模的方法，快速实现全局最优的聚类中心，类内评价最优代表作为聚类中心，保证类特性的持续性和强壮性，而且解决了K－means聚类的参数选择问题，最后采用TM多光谱遥感图象进行参数分析和算法比较，验证了该算法分类快速准确，且参数控制灵活，因此基于小波特征抽取和模拟退火的多光谱遥感图象快速聚类算法有较好的应用前景。     

An edge-based approach for the segmentation of 3-D range images of small industrial-like objects

An edge-based approach for the segmentation of 3-D range images of small industrial-like objects is presented. It is illustrated that the gradient edge operators are mostly suitable for detecting jump boundaries. They may produce misleading responses and may also miss detecting roof edges. We also show, using numerical analysis techniques, that the residual norms of fitting planes at surface points where the residuals are measured in the z-direction have large magnitudes at the jump boundaries. At the folds or creases they have large enough magnitudes but are shifted by one pixel from the crease. We show however that the residual norms of the fitting planes where the residuals are measured in the direction normal to the planes are more suitable for detecting the various image edges. Experimental results for the segmentation of 3-D range images of small industrial-like objects, using the histograms of such residual norms are given with comments.     

一种高效检测图像中是否有三角形的算法

在停车场的停车位检测系统中,要识别停车位是否空闲,就必须对检测系统获取的图像中的任何可能停靠在停车场中的汽车进行识别,但由于汽车种类、形状、大小等千变万化,因此通过识别图像中是否有汽车来判断停车位是否空闲是不现实的。由于可以先在每个停车位上画上一个实心黑三角形,然后通过识别图像中是否包含有三角形来判断停车位是否空闲,如果图像中没有实心黑三角形,则表明该停车位已经被汽车所占据;否则表明停车位空闲,因此,对空闲停车位的检测就转换为检测图像中是否有三角形,这要比识别所有的汽车容易得多。而传统的Hough变换则不能有效地检测图像中是否包含有三角形,为了准确检测三角形,提出了一种有效的检测图像中是否有三角形的算法。该算法首先利用Sobel算子检测出图像的边缘信息;然后抽取一条连通的边缘,并对当前抽取出来的连通边缘所围成的区域进行填充;接着利用三角形面积与它的3条边的关系来判断当前被填充的区域是否是三角形。当分析完该条边缘后,再继续抽取图像中的下一条边缘进行分析,如此反复,直到图像中的所有边缘被抽取完,则停止循环;最后输出结果,如果图像中有三角形,则输出三角形的个数;如果图像中没有三角形,则输出0。实践表明,该算法具有运算量小、运算速度快、所需内存少的优点。     

An image fusion method based on object-oriented classification

In image fusion of different spatial resolution multispectral (MS) and panchromatic (PAN) images, a spectrally mixed MS pixel superimposes multiple mixed PAN pixels and multiple pure PAN pixels. This verifies that with increased spatial resolution in imaging, a low spatial resolution spectrally mixed subpixel may be unmixed to be a pure pixel. However, spectral unmixing of mixed MS subpixels is rarely considered in current remote-sensing image fusion methods, resulting in blurred fused images. In the image fusion method proposed in this article, such spectral unmixing is realized. In this method, the MS and PAN images are jointly segmented into image objects, image objects are classified to obtain a classification map of the PAN image and each MS subpixel is fused to be a pixel matching the class of the corresponding PAN pixel. Tested on spatially degraded IKONOS MS and PAN images with a significant spatial resolution ratio of 8:1, the fusion method offered fused images with high spectral quality and deblurred visualization.     

多门限二进制编码方法在TM 图像处理中的应用

不同类型的地物具有不同的反射光谱, 在多维光谱空间中构成不同的特征向量, 这便是遥感多光谱图像分析与识别的物理依据。传统方法中有基于单个像元波段亮度的、空间纹理的、变换空间的多光谱图像特征提取与分析方法, 但这些方法并没有直接描述地物的最本质特征-反射光谱曲线。从20 世纪80 年代开始, 当二进制编码的方法提出并在多光谱匹配识别中获得成功应用后,多光谱图像分析处理便可以在这种特征提取的基础上, 研究新的方法。提出一种基于多门限二进制编码的光谱形状描述方法, 这种方法的核心就是将多光谱的亮度范围细分成若干个灰度区间, 也称为多门限, 分别将各波段光谱亮度与多门限进行比较, 从而建立一列能够较详细描述光谱形状的二进制编码, 我们将这种新的特征描述方法应用于多光谱图像的分类、信息提取和变化检测。遥感图像处理实验的结果表明, 这种方法是有效的。     

各向异性扩散的遥感图像边缘增强方法

为解决遥感图像边缘增强过程中辨识弱边缘和噪声的问题,提出一种改进的模糊各向异性边缘增强方法。根据非下采样轮廓波变换系数分布特征,获得像素几何结构信息;并基于各像素在不同子带的系数分布特征和噪声方差,分析其均值和最大值的模糊隶属度;利用模糊推理计算扩散系数,更好地控制各向异性扩散过程。实验结果显示,该方法具有更好的边缘增强和抑噪性能,能有效地辨识弱边缘和降低时间复杂度。     

Phase correlation pixel‐to‐pixel image co‐registration based on optical flow and median shift propagation

With singular value decomposition (SVD) and robust 2‐dimensional fitting phase correlation algorithms, it is possible to achieve pixel‐to‐pixel image co‐registration at sub‐pixel accuracy via local feature matching. However, the method often fails in featureless and low correlation areas making it not robust for co‐registration of images with considerable spectral differences and large featureless ground objects. A median shift propagation (MSP) technique is proposed to eliminate the problem, in a phase correlation and Normalized Cross‐Correlation (NCC) combined approach. The experiment results using images from different sensor platforms and spectral bands indicate that the new method is very robust to featureless and low correlation areas and can achieve very accurate pixel‐to‐pixel image co‐registration with good tolerance of spectral and spatial differences between images. The method will significantly improve change detection in various remote sensing applications.     

基于地物反射特性的多波段遥感图像无损压缩方法

要实现多波段遥感图像的无损压缩,去除空间和谱间的相关性是其中的重要环节。通过分类,分析不同地物在不同波段的反射特性,再根据不同地物的波段反射特性构造出针对不同地物的谱间预测器,用以去除谱间相关性。对于去除谱间相关的残差图像,采用Ｓ＋ Ｐ变换,以去除空间相关。实验取得了令人满意的效果,证明了这种方法的有效性。     

RX architectures for real-time anomaly detection in hyperspectral images

In the field of hyperspectral image processing, anomaly detection (AD) is a deeply investigated task whose goal is to find objects in the image that are anomalous with respect to the background. In many operational scenarios, detection, classification and identification of anomalous spectral pixels have to be performed in real time to quickly furnish information for decision-making. In this framework, many studies concern the design of computationally efficient AD algorithms for hyperspectral images in order to assure real-time or nearly real-time processing. In this work, a sub-class of anomaly detection algorithms is considered, i.e., those algorithms aimed at detecting small rare objects that are anomalous with respect to their local background. Among such techniques, one of the most established is the Reed–Xiaoli (RX) algorithm, which is based on a local Gaussian assumption for background clutter and locally estimates its parameters by means of the pixels inside a window around the pixel under test (PUT). In the literature, the RX decision rule has been employed to develop computationally efficient algorithms tested in real-time systems. Initially, a recursive block-based parameter estimation procedure was adopted that makes the RX processing and the detection performance differ from those of the original RX. More recently, an update strategy has been proposed which relies on a line-by-line processing without altering the RX detection statistic. In this work, the above-mentioned RX real-time oriented techniques have been improved using a linear algebra-based strategy to efficiently update the inverse covariance matrix thus avoiding its computation and inversion for each pixel of the hyperspectral image. The proposed strategy has been deeply discussed pointing out the benefits introduced on the two analyzed architectures in terms of overall number of elementary operations required. The results show the benefits of the new strategy with respect to the original architectures.     

光谱与形状特征相结合的道路提取方法研究

针对从遥感影像上提取道路,目前已经有很多研究,但尚有许多问题有待解决。如果仅从光谱特征分类入手提取道路,会存在“异物同谱”问题。为解决这个问题,提出了用光谱特征与形状特征相结合的方法提取道路。提出了3个形状指数描述道路的形状特征。以SPOT卫星影像为例,将高空间分辨率的全色图像与多光谱图像融合,首先基于道路光谱特征进行图像分类,然后再应用道路的形状特征去除分类图像中的“异物”目标。研究结果表明该方法能有效地从遥感影像中提取主干道路。     

A practical method for constructing the mixture model for a spectral class

Remotely sensed multispectral image data are found in grouped form with (say) s spectral components (bands). In this study, a practical method for constructing a mixture model or the probability density function of the mixture of k (3 =< k =< s) normal distributions for a spectral class is given. A new method for estimation of the mixing proportions of spectral components (bands) in the remotely sensed multispectral image data is proposed with the assumption that the spectral component (band) means are different from each other.