Kernel Function in SVM-RFE based Hyperspectral Data band Selection

Supporting vector machine recursive feature elimination (SVM-RFE) has a low efficiency when it is applied to band selection for hyperspectral dada,since it usually uses a non-linear kernel and trains SVM every time after deleting a band.Recent research shows that SVM with non-linear kernel doesn’t always perform better than linear one for SVM classification.Similarly,there is some uncertainty on which kernel is better in SVM-RFE based band selection.This paper compares the classification results in SVM-RFE using two SVMs,then designs two optimization strategies for accelerating the band selection process:the percentage accelerated method and the fixed accelerated method.Through an experiment on AVIRIS hyperspectral data,this paper found:① Classification precision of SVM will slightly decrease with the increasing of redundant bands,which means SVM classification needs feature selection in terms of classification accuracy;② The best band collection selected by SVM-RFE with linear SVM that has higher classification accuracy and less effective bands than that with non-linear SVM;③ Both two optimization strategies improved the efficiency of the feature selection,and percentage eliminating performed better than fixed eliminating method in terms of computational efficiency and classification accuracy.     

Unsupervised hyperspectral feature selection based on fuzzy c-means and grey wolf optimizer

Hyperspectral image (HSI) with hundreds of narrow and consecutive spectral bands provides substantial information to discriminate various land-covers. However, the existence of redundant features/bands not only gives rise to increasing of computation time but also interferes the classification result of hyperspectral images. Obviously, it is a very challenging problem how to select an effective feature subset from original bands to reduce the dimensionality of the hyperspectral dataset. In this study, a novel unsupervised feature selection method is suggested to remove the redundant features of HSI by feature subspace decomposition and optimization of feature combination. Feature subset decomposition is achieved by the fuzzy c-means (FCM) algorithm. The optimal feature selection is based on the optimization process of grey wolf optimizer (GWO) algorithm and maximum entropy (ME) principle. To evaluate the effectiveness of the proposed method, experiments are conducted on three well-known hyperspectral datasets, Indian Pines, Pavia University, and Salinas. Six state-of-the-art feature selection methods are used to compare with the proposed method. Experimental results successfully confirm the superior performance of our proposal with respect to three classification accuracy indices overall accuracy (OA), average accuracy (AA) and kappa coefficient (κ).     

面向分类应用的高光谱谱段选择方法

高光谱数据在物质分类识别领域得到了广泛应用,但存在数据量大、波段间相关性高等问题,严重影响分类精度及应用。针对以上问题分析了已有的波段选择方法,提出了基于波段聚类及监督分类的遗传算法,对高光谱数据进行波段选择：采用[K]均值聚类算法对波段数据进行聚类分析,构造波段子集合;利用分类器族分类精度构造适应度函数,采用遗传算法对波段子集合进行优化选择。最后用阔叶林高光谱数据对提出的算法进行对比实验,实验结果表明针对分类应用,提出的算法能够非常有效地选择高光谱谱段。     

Gray Wolf Optimizer for hyperspectral band selection

In this paper, we propose a new optimization-based framework to reduce the dimensionality of hyperspectral images. One of the most problems in hyperspectral image classification is the Hughes phenomenon caused by the irrelevant spectral bands and the high correlation between the adjacent bands. The problematic is how to find the relevant bands to classify the pixels of hyperspectral image without reducing the classification accuracy rate. We propose to reformulate the problem of band selection as a combinatorial problem by modeling an objective function based on class separability measures and the accuracy rate. We use the Gray Wolf Optimizer, which is a new meta-heuristic algorithm more efficient than Practical Swarm Optimization, Gravitational Search Algorithm, Differential Evolution, Evolutionary Programming and Evolution Strategy. The experimentations are performed on three widely used benchmark hyperspectral datasets. Comparisons with the state-of-the-art approaches are also conducted. The analysis of the results proves that the proposed approach can effectively investigate the spectral band selection problem and provides a high classification accuracy rate by using a few samples for training.     

基于邻域熵的高光谱波段选择算法

为了减少高光谱图像数据中的冗余信息,优化计算效率,并提升图像数据后续应用的有效性,提出一种基于邻域熵(NE)的高光谱波段选择算法.首先,为了高效计算样本的邻域子集,采用了局部敏感哈希(LSH)作为近似最近邻的搜索策略;然后,引入了NE理论来度量波段和类之间的互信息(MI),并把最小化特征集合与类变量之间的条件熵作为选取...     

An effective feature selection method for hyperspectral image classification based on genetic algorithm and support vector machine

With the development and popularization of the remote-sensing imaging technology, there are more and more applications of hyperspectral image classification tasks, such as target detection and land cover investigation. It is a very challenging issue of urgent importance to select a minimal and effective subset from those mass of bands. This paper proposed a hybrid feature selection strategy based on genetic algorithm and support vector machine (GA–SVM), which formed a wrapper to search for the best combination of bands with higher classification accuracy. In addition, band grouping based on conditional mutual information between adjacent bands was utilized to counter for the high correlation between the bands and further reduced the computational cost of the genetic algorithm. During the post-processing phase, the branch and bound algorithm was employed to filter out those irrelevant band groups. Experimental results on two benchmark data sets have shown that the proposed approach is very competitive and effective.     

基于核模糊粗糙集的高光谱波段选择算法

为了减少高光谱波段图像间的冗余,降低运算时间,为后续分类任务提供有效支持,提出了基于核模糊粗糙集的高光谱波段选择算法。高光谱图像相邻波段间相似性较强,为进一步有效地度量波段的重要性,引入核模糊粗糙集理论。考虑波段中类的分布特性,根据波段的下近似集分布定义波段间的相关性,进而结合波段的信息熵定义波段的重要度。采用最大相关性最大重要度的搜索策略对高光谱图像进行波段选择。最后在常用高光谱数据集Indiana Pines农业区上,采用J48及KNN分类器进行测试。与其他高光谱波段选择算法相比,该算法在两个分类器上的总体平均分类精度分别提升了4.5和6.6个百分点。实验结果表明所提算法在处理高光谱波段选择问题时具有一定优势。     

基于类别可分性的高光谱图像波段选择

高光谱遥感数据具有丰富的光谱信息,应用十分广泛,但其冗余的光谱信息有时会限制高光谱图像的分类等的精度以及计算复杂度.为了提高解译效率,高光谱图像降维不可或缺,这也是高光谱图像处理的研究热点之一.提出了一种基于类别可分性的高光谱图像波段选择方法(Endmember Separability Based band Selection,ESBB),该方法通过Mahalanobis距离最大化图像中各类地物的可分性来确定最优的波段组合.相较于其他监督波段选择算法,该方法不需要大量训练样本,不用对每个组合做分类处理.对波段选择后的结果进行分类的实验结果证明,该方法是一个快速有效的波段选择方法,可以得到一个较好的分类精度.     

基于多核模糊粗糙集与蝗虫优化算法的高光谱波段选择

波段选择能有效减少高光谱数据的空间冗余,为后续分类提供有效的支持。多核模糊粗糙集模型能够对包含不确定性的数值数据进行分析和近似描述,而蝗虫优化算法对优化问题求解具有较强的探索和开发能力,因而将多核模糊粗糙集模型引入高光谱的不确定性分析建模中,采用蝗虫优化算法对波段子集进行选择,提出了一种基于多核模糊粗糙集与蝗虫优化算法的高光谱波段选择算法。首先,使用多核算子来进行相似性度量,提高模型对数据分布的适应性。定义基于核模糊粗糙集的波段相关性度量,通过模糊粗糙集中不同像素点地物上的下近似分布来度量波段之间的相关性。然后,综合考虑波段依赖度、波段信息熵、波段间相关性来定义波段子集的适应度函数。最后,在常用高光谱数据集Indiana Pines农业区上,采用J48和K近邻(KNN)作为分类算法,把所提算法与波段相关性分析(BCA)、标准化互信息(NMI)算法进行分类性能比较。实验结果表明,在选取较少波段个数时,所提算法的总体平均分类精度提高了2.46和1.54个百分点。     

Band Selection of Hyperspectral Images for Automatic Detection of Poultry Skin Tumors

This paper presents a spectral band selection method for feature dimensionality reduction in hyperspectral image analysis for detecting skin tumors on poultry carcasses. A hyperspectral image contains spatial information measured as a sequence of individual wavelength across broad spectral bands. Despite the useful information for skin tumor detection, real-time processing of hyperspectral images is often a challenging task due to the large amount of data. Band selection finds a subset of significant spectral bands in terms of information content for dimensionality reduction. This paper presents a band selection method of hyperspectral images based on the recursive divergence for the automatic detection of poultry carcasses. For this, we derive a set of recursive equations for the fast calculation of divergence with an additional band to overcome the computational restrictions in real-time processing. A support vector machine is used as a classifier for tumor detection. From our experiments, the proposed band selection method shows high detection accuracy with low false positive rates compared to the canonical analysis at a small number of spectral bands. Also, compared with the enumeration approach of 93.75% detection rate, our proposed recursive divergence approach gives 90.6% detection rate, which is within the industry-accepted accuracy of 90-95%, while achieving the computational saving for real-time processing.     

基于熵加权K-means全局信息聚类的高光谱图像分类

目的 高光谱图像波段数目巨大，导致在解译及分类过程中出现“维数灾难”的现象。针对该问题，在K-means聚类算法基础上，考虑各个波段对不同聚类的重要程度，同时顾及类间信息，提出一种基于熵加权K-means全局信息聚类的高光谱图像分类算法。方法 首先，引入波段权重，用来刻画各个波段对不同聚类的重要程度，并定义熵信息测度表达该权重。其次，为避免局部最优聚类，引入类间距离测度实现全局最优聚类。最后，将上述两类测度引入K-means聚类目标函数，通过最小化目标函数得到最优分类结果。结果 为了验证提出的高光谱图像分类方法的有效性，对Salinas高光谱图像和Pavia University高光谱图像标准图中的地物类别根据其光谱反射率差异程度进行合并，将合并后的标准图作为新的标准分类图。分别采用本文算法和传统K-means算法对Salinas高光谱图像和Pavia University高光谱图像进行实验，并定性、定量地评价和分析了实验结果。对于图像中合并后的地物类别，光谱反射率差异程度大，从视觉上看，本文算法较传统K-means算法有更好的分类结果；从分类精度看，本文算法的总精度分别为92.20%和82.96%， K-means算法的总精度分别为83.39%和67.06%，较K-means算法增长8.81%和15.9%。结论 提出一种基于熵加权K-means全局信息聚类的高光谱图像分类算法，实验结果表明，本文算法对高光谱图像中具有不同光谱反射率差异程度的各类地物目标均能取得很好的分类结果。     

Fast hyperspectral band selection based on spatial feature extraction

Hyperspectral images usually consist of hundreds of spectral bands, which can be used to precisely characterize different land cover types. However, the high dimensionality also has some disadvantages, such as the Hughes effect and a high storage demand. Band selection is an effective method to address these issues. However, most band selection algorithms are conducted with the high-dimensional band images, which will bring high computation complexity and may deteriorate the selection performance. In this paper, spatial feature extraction is used to reduce the dimensionality of band images and improve the band selection performance. The experiment results obtained on three real hyperspectral datasets confirmed that the spatial feature extraction-based approach exhibits more robust classification accuracy when compared with other methods. Besides, the proposed method can dramatically reduce the dimensionality of each band image, which makes it possible for band selection to be implemented in real time situations.     

Hyperspectral band selection with objective image quality assessment

Hyperspectral sensors often collect hundreds of bands at a time, so hyperspectral images can accurately characterize different land-cover types with abundant spectral information. However, these spectral bands also contain redundant information that needs to be removed. Band selection is one of the most widely used methods to remove noised or redundant bands. Because labelled samples are difficult to collect, most band selection methods adopt unsupervised ways to select diverse and representative bands. Still, noised bands are often selected because they usually have low correlation with other bands. In this article, objective image quality assessment is introduced to indicate the quality of every band, and combined with the redundancy measure, a new unsupervised band selection method is proposed. Three real hyperspectral images are used to demonstrate the effectiveness of the proposed algorithm.     

Multidimensional local spatial autocorrelation measure for integrating spatial and spectral information in hyperspectral image band selection

Hyperspectral band selection aims at the determination of an optimal subset of spectral bands for dimensionality reduction without loss of discriminability. Many conventional band selection approaches depend on the concept of “statistical distance” measure between the probability distributions characterizing sample classes. However, the maximization of separability does not necessarily guarantee that a classification process results in the best classification accuracies. This paper presents a multidimensional local spatial autocorrelation (MLSA) measure that quantifies the spatial autocorrelation of the hyperspectral image data. Based on the proposed spatial measure, a collaborative band selection strategy is developed that combines both spectral separability measure and spatial homogeneity measure for hyperspectral band selection without losing the spectral details useful in classification processes. The selected band subset by the proposed method shows both larger separability between classes and stronger spatial similarity within class. Case studies in biomedical and remote sensing applications demonstrate that the MLSA-based band selection approach improves object classification accuracies in hyperspectral imaging compared with conventional approaches.     

基于自动子空间划分的高光谱数据特征提取

针对遥感高光谱图像数据量大、维数高的特点,提出了一种自动子空间划分方法用于高光谱图像数据量减小处理。该方法主要包括3个处理步骤:数据空间划分,子空间主成分分析和基于类别可分性准则的特征选择。该方法充分利用了高光谱图像各波段数据之间的局部相关性,将整个数据划分为若干个具有较强相关性的独立子空间,然后在子空间内利用主成分分析进行特征提取,根据各类地物间的类别可分性选择有效特征,最后利用地物分类来验证该方法的有效性。实验结果表明,该方法能够有效地实现高光谱图像数据维数减小和特征提取,同现有的自适应子空间分解方法和分段主成分变换方法相比,该方法所提取的特征用于分类时能获得较好的分类精度。利用该方法进行处理,当高光谱数据维数降低了90%时,9类地物分类实验的总体分类精度可以达到80.2%。     

自适应插值与特征压缩的小样本数据分类研究

大数据的类别不平衡与维度爆炸问题严重影响着算法的预测效率和分类精度。因此,提出了一种基于插值与特征压缩的大数据分类方法ASE-RFXT。改进ADASYN（adaptive synthetic sampling approach）的插值中心,减少了噪声的引入,改善了少数类样本的分布。改进ReliefF（特征权重法）,并将它与集成算法XGDT（extreme gradient dart tree）结合对特征进行并行加权,减少了权重受异常值的影响,使得评估更加准确。利用特征之间的相关性过滤低权重冗余特征,以XGDT的分类精度为评价指标通过SFS（sequential forward selection）压缩特征。实验结果表明ASE-RFXT方法可以降低特征维度,节约训练时间,提高不平衡小样本数据的分类精度。     

基于特征加权的高光谱图像融合分类

在对高光谱图像监督分类中, 传统的监督学习方法对高光谱数据进行分类时需要获取足够的有标记样本作为训练样本, 这样可以有效的避免Hughes效应. 实际情况下的高光谱数据拥有较多的波段和相对较小的训练样本集给传统的遥感图像分类方法带来了挑战. 因此, 提出了一种基于特征组合以及特征加权的高光谱图像分类算法, 针对纹理特征分析难度较大的现实, 利用一阶直方图的统计特征描述图像纹理特征, 通过类内散度矩阵的逆矩阵作为特征加权矩阵构造组合核函数将高光谱光谱特征和空间特征融合起来, 同时利用特征加权的方法用于提高小训练样本的监督分类精度. 实验结果表明, 本文所提的方法对小样本的高光谱数据分类具有良好的效果.     

New framework for hyperspectral band selection using modified wind-driven optimization algorithm

The presence of irrelevant and highly correlated spectral bands significantly reduces the classification accuracy of the hyperspectral images. Therefore, the selection of suitable bands from the set of available spectral bands plays a crucial role in improving the classification accuracy. In this paper, a novel band selection approach is proposed based on nature inspired meta-heuristic algorithm to mitigate the effect of curse of dimensionality. Wind-driven optimization (WDO), among other meta-heuristic algorithms, has proven to be more efficient in solving global optimization problems. However, WDO is prone to premature convergence when solving the global optimization problem due to loss of diversity of air particles. Therefore, a modified WDO (MWDO) is proposed for band selection, which is able to avoid the premature convergence and control the exploration–exploitation search trade-off. Finally, in order to further improve the performance of the classification, the selected bands are fed into the deep learning architecture to extract the high-level useful features. The experiments are carried on three widely used standard datasets such as Indian Pines, Pavia University, and Salinas. The experimental results show that the proposed approach selects an optimal subset of bands with good convergence characteristics and provide high classification accuracy with fewer bands in comparison with other approaches. The proposed method achieves an overall accuracy of 93.26%, 94.76%, and 95.96% for Indian Pines, Pavia University, and Salinas datasets, respectively.     

基于波段影像统计信息量加权K-means聚类的高光谱影像分类

针对分类过程中如何合理利用高光谱影像波段问题,提出一种基于波段影像统计量加权K-means聚类的高光谱影像分类算法.该算法的核心思想在于:由波段含有的信息量及波段间的相关性确定各波段权重,同时考虑各波段对各聚类的重要性.首先,根据波段影像的熵、标准差及均值定义波段信息量函数,根据相邻波段影像互信息定义相关性函数;其次,由上述波段信息量函数及波段间相关性函数定义波段权重函数;然后,结合波段权重和波段-类属权重定义规则化目标函数;最后,依据参数特性设计目标函数求解方案.对Salinas高光谱影像和Pavia Centre高光谱影像分别采用所提出的算法与传统K-means算法、PCA$+K$-means算法及子空间波段选择$+K$-means算法进行对比实验,对于总精度及Kappa系数,所提出的算法都高于其他3种对比算法,结果验证了所提出算法的有效性.相对于其他3种算法而言,所提出的算法可有效改善高光谱影像分类的性能.     

分段2维主成分分析的超光谱图像波段选择

目的 超光谱图像具有极高的谱间分辨率,巨大的数据量给分类识别等后续处理带来很大压力。为了有效降低图像数据维数,提出基于分段2DPCA的超光谱图像波段选择算法。方法 首先根据谱间相关性对原始图像进行波段分组,然后根据主成分反映每个光谱波段的信息比重分别对每组图像进行波段选择,从而实现超光谱图像的谱间降维。结果 该算法有效降低了超光谱图像的光谱维数,选择的波段明显反映出不同地物像元矢量的区别。结论 实验结果表明,该波段选择算法相对传统算法速度更快,并且较好地保留了原始图像的局部重要信息,对后续处理有积极意义。