Enhanced hyperspectral imagery representation via diffusion geometric coordinates

The concise and informative representation of hyperspectral imagery is achieved via the introduced diffusion geometric coordinates derived from nonlinear dimension reduction maps - diffusion maps. The huge-volume high- dimensional spectral measurements are organized by the affinity graph where each node in this graph only connects to its local neighbors and each edge in this graph represents local similarity information. By normalizing the affinity graph appropriately, the diffusion operator of the underlying hyperspectral imagery is well-defined, which means that the Markov random walk can be simulated on the hyperspectral imagery. Therefore, the diffusion geometric coordinates, derived from the eigenfunctions and the associated eigenvalues of the diffusion operator, can capture the intrinsic geometric information of the hyperspectral imagery well, which gives more enhanced representation results than traditional linear methods, such as principal component analysis based methods. For large-scale full scene hyperspectral imagery, by exploiting the backbone approach, the computation complexity and the memory requirements are acceptable. Experiments also show that selecting suitable symmetrization normalization techniques while forming the diffusion operator is important to hyperspectral imagery representation.

DIMENSIONALITY REDUCTION FOR HYPERSPECTRAL IMAGERY BASED ON FASTICA

The high dimensions of hyperspectral imagery have caused burden for further processing. A new Fast Independent Component Analysis (FastICA) approach to dimensionality reduction for hyperspectral imagery is presented. The virtual dimensionality is introduced to determine the number of dimensions needed to be preserved. Since there is no prioritization among independent components generated by the FastICA,the mixing matrix of FastICA is initialized by endmembers,which were extracted by using unsupervised maximum distance method. Minimum Noise Fraction (MNF) is used for preprocessing of original data,which can reduce the computational complexity of FastICA significantly. Finally,FastICA is performed on the selected principal components acquired by MNF to generate the expected independent components in accordance with the order of endmembers. Experimental results demonstrate that the proposed method outperforms second-order statistics-based transforms such as principle components analysis.

Abundance quantification by independent component analysis of hyperspectral imagery for oil spill coverage calculation

The estimation of oil spill coverage is an important part of monitoring of oil spills at sea.The spatial resolution of images collected by airborne hyper-spectral remote sensing limits both the detection of oil spills and the accuracy of estimates of their size.We consider at-sea oil spills with zonal distribution in this paper and improve the traditional independent component analysis algorithm.For each independent component we added two constraint conditions:non-negativity and constant sum.We use priority weighting by higher-order statistics,and then the spectral angle match method to overcome the order nondeterminacy.By these steps,endmembers can be extracted and abundance quantified simultaneously.To examine the coverage of a real oil spill and correct our estimate,a simulation experiment and a real experiment were designed using the algorithm described above.The result indicated that,for the simulation data,the abundance estimation error is 2.52% and minimum root mean square error of the reconstructed image is 0.030 6.We estimated the oil spill rate and area based on eight hyper-spectral remote sensing images collected by an airborne survey of Shandong Changdao in 2011.The total oil spill area was 0.224 km^2,and the oil spill rate was 22.89%.The method we demonstrate in this paper can be used for the automatic monitoring of oil spill coverage rates.It also allows the accurate estimation of the oil spill area.

Mapping spatial variation in acorn production from airborne hyperspectral imagery

Masting is a well-marked variation in yields of oak forests. In Japan, this phenomenon is also related to wildlife management and oak regeneration practices. This study demonstrates the capability of integrating remote sensing techniques into map- ping spatial variation of acorn production. The hyperspectral images in 72 wavelengths （407-898 nm） were acquired over the study area ten times over a period of three years （2003-2005） during the early growing season of Quercus serrata using the Airborne Im- aging Spectrometer Application （AISA） Eagle System. With the canopy spectral reflectance values of 22 sample trees extracted from the images, yield estimation models were developed via multiple linear regression （MLR） analyses. Using the object-oriented classi- fication approach in eCognition, canopies representative of individual oak trees （Q. serrata） were identified from the corresponding hyperspectral imagery and combined with the fitted estimation models developed, acorn yield over the entire forest were estimated and visualized into maps. Three estimation models, obtained for June 27 in 2003, July 13 in 2004 and June 21 in 2005, showed good performance in acorn yield estimation both for the training and validation datasets, all with R2 〉 0.4, p 〈 0.05 and RRMSE 〈 1 （the relative root mean square of error）. The present study shows the potential of airborne hyperspectral imagery not only in estimating acorn yields during early growing seasons, but also in identifying Q. serrata from other image objects, based on which of the spatial distribution patterns of acorn production over large areas could be mapped. The yield map can provide within-stand abundance and valuable information for the size and spatial synchrony of acorn production.

Denoising of hyperspectral imagery by cubic smoothing spline in the wavelet domain

The acquired hyperspectral images （HSIs） are inherently attected by noise wlm Dano-varylng level, which cannot be removed easily by current approaches. In this study, a new denoising method is proposed for removing such kind of noise by smoothing spectral signals in the transformed multi- scale domain. Specifically, the proposed method includes three procedures： 1 ） applying a discrete wavelet transform （DWT） to each band; 2） performing cubic spline smoothing on each noisy coeffi- cient vector along the spectral axis; 3 ） reconstructing each band by an inverse DWT. In order to adapt to the band-varying noise statistics of HSIs, the noise covariance is estimated to control the smoothing degree at different spectra｜ positions. Generalized cross validation （GCV） is employed to choose the smoothing parameter during the optimization. The experimental results on simulated and real HSIs demonstrate that the proposed method can be well adapted to band-varying noise statistics of noisy HSIs and also can well preserve the spectral and spatial features.

Inversion of maize leaf nitrogen using UAV hyperspectral imagery in breeding fields

Nitrogen(N)as a pivotal factor in influencing the growth,development,and yield of maize.Monitoring the N status of maize rapidly and non-destructive and real-time is meaningful in fertilization management of agriculture,based on unmanned aerial vehicle(UAV)remote sensing technology.In this study,the hyperspectral images were acquired by UAV and the leaf nitrogen content(LNC)and leaf nitrogen accumulation(LNA)were measured to estimate the N nutrition status of maize.24 vegetation indices(VIs)were constructed using hyperspectral images,and four prediction models were used to estimate the LNC and LNA of maize.The models include a single linear regression model,multivariable linear regression(MLR)model,random forest regression(RFR)model,and support vector regression(SVR)model.Moreover,the model with the highest prediction accuracy was applied to invert the LNC and LNA of maize in breeding fields.The results of the single linear regression model with 24 VIs showed that normalized difference chlorophyll(NDchl)had the highest prediction accuracy for LNC(R^(2),RMSE,and RE were 0.72,0.21,and 12.19%,respectively)and LNA(R^(2),RMSE,and RE were 0.77,0.26,and 14.34%,respectively).And then,24 VIs were divided into 13 important VIs and 11 unimportant VIs.Three prediction models for LNC and LNA were constructed using 13 important VIs,and the results showed that RFR and SVR models significantly enhanced the prediction accuracy of LNC and LNA compared to the multivariable linear regression model,in which RFR model had the highest prediction accuracy for the validation dataset of LNC(R^(2),RMSE,and RE were 0.78,0.16,and 8.83%,respectively)and LNA(R^(2),RMSE,and RE were 0.85,0.19,and 9.88%,respectively).This study provides a theoretical basis for N diagnosis and precise management of crop production based on hyperspectral remote sensing in precision agriculture.

A background refinement method based on local density for hyperspectral anomaly detection

For anomaly detection,anomalies existing in the background will affect the detection performance.Accordingly,a background refinement method based on the local density is proposed to remove the anomalies from thebackground.In this work,the local density is measured by its spectral neighbors through a certain radius which is obtained by calculating the mean median of the distance matrix.Further,a two-step segmentation strategy is designed.The first segmentation step divides the original background into two subsets,a large subset composed by background pixels and a small subset containing both background pixels and anomalies.The second segmentation step employing Otsu method with an aim to obtain a discrimination threshold is conducted on the small subset.Then the pixels whose local densities are lower than the threshold are removed.Finally,to validate the effectiveness of the proposed method,it combines Reed-Xiaoli detector and collaborative-representation-based detector to detect anomalies.Experiments are conducted on two real hyperspectral datasets.Results show that the proposed method achieves better detection performance.

An Intelligent Deep Learning Based Xception Model for Hyperspectral Image Analysis and Classification

Due to the advancements in remote sensing technologies,the generation of hyperspectral imagery(HSI)gets significantly increased.Accurate classification of HSI becomes a critical process in the domain of hyperspectral data analysis.The massive availability of spectral and spatial details of HSI has offered a great opportunity to efficiently illustrate and recognize ground materials.Presently,deep learning(DL)models particularly,convolutional neural networks(CNNs)become useful for HSI classification owing to the effective feature representation and high performance.In this view,this paper introduces a new DL based Xception model for HSI analysis and classification,called Xcep-HSIC model.Initially,the presented model utilizes a feature relation map learning(FRML)to identify the relationship among the hyperspectral features and explore many features for improved classifier results.Next,the DL based Xception model is applied as a feature extractor to derive a useful set of features from the FRML map.In addition,kernel extreme learning machine(KELM)optimized by quantum-behaved particle swarm optimization(QPSO)is employed as a classification model,to identify the different set of class labels.An extensive set of simulations takes place on two benchmarks HSI dataset,namely Indian Pines and Pavia University dataset.The obtained results ensured the effective performance of the XcepHSIC technique over the existing methods by attaining a maximum accuracy of 94.32%and 92.67%on the applied India Pines and Pavia University dataset respectively.

新一代国产高光谱ZY1-02E卫星在内陆水体水质参数反演中的应用

2021年12月26日,我国成功发射资源一号02E(ZY1-02E)卫星,其搭载了新一代高光谱相机(Advanced Hyperspectral Imager,AHSI),拥有30 m空间分辨率的可见光到短波红外范围内的166个波段,在内陆水体水质参数反演方面具有重要潜力。本研究以北京市沙河水库和金海湖为研究区,开展基于ZY1-02E AHSI影像数据的叶绿素a浓度和透明度反演研究,以评价其实际应用效果。基于京津冀地区12个湖库的遥感反射率和叶绿素a浓度实测数据,构建叶绿素a反演半经验模型。将该模型和基于准解析算法(Quasi-Analytical Algorithm,QAA)的透明度半分析模型应用于ZY1-02E AHSI影像,并利用在沙河水库和金海湖两个研究区获取的星地同步实测水质数据对反演结果进行精度评价。结果表明,基于670 nm和705 nm波长的归一化指数的叶绿素a反演半经验模型的精度最高,拟合度和平均相对误差分别为0.79和21.70%;基于QAA-V6的透明度半分析模型的精度最高,拟合度和平均相对误差分别为0.93和13.90%。该研究结果初步证明了ZY1-02E高光谱数据在内陆水体水质参数反演中的潜力。

Comparison of three models for winter wheat yield prediction based on UAV hyperspectral images

Predicting crop yield timely can considerably accelerate agricultural production management and food policy-making,which are also important requirements for precise agricultural development.Given the development of hyperspectral imaging technology,a simple and efficient modeling method is convenient for predicting crop yield by using airborne hyperspectral images.In this study,the Unmanned Aerial Vehicle(UAV)hyperspectral and maturity yield data in 2014-2015 and 2017-2018 were collected.The winter wheat yield prediction model was established by optimizing Vegetation Indices(VIs)feature scales and sample scales,incorporating Partial Least Squares Regression(PLSR),Random Forest algorithm(RF),and Back Propagation Neural Network algorithm(BPN).Results showed that PLSR stands out as the optimal wheat yield prediction model considering stability and accuracy(RMSE=948.88 kg/hm2).Contrary to the belief that more input features result in higher accuracy,PLSR,RF,and BPN models performed best when trained with the top 3,8,and 4 VIs with the highest correlation,respectively.With an increase in training samples,model accuracy improves,reaching stability when the training samples reach 70.Using PLSR and optimal feature scales,UAV yield prediction maps were generated,holding significant value for field management in precision agriculture.

“资源一号”02E卫星高原地区植被生态调查应用评价

为分析评价“资源一号”02E卫星多光谱和高光谱数据在高原地区植被生态调查中的应用能力,选择滇东北会泽-东川植被垂直分带特征明显区域作为研究区,对多光谱影像进行目视解译和植被指数提取,并选取空间分辨率和成像时间相近的“高分一号”和“哨兵2号”等卫星数据开展对比分析;对高光谱影像采用支持向量机法、神经网络法、光谱角分类法等开展高原地区山地植被垂直分带特征分析、典型植被类型提取,并结合野外实测光谱和林业调查资料进行对比分析,评价其应用效果。结果表明:“资源一号”02E卫星多光谱影像,其主要植被类型影像特征清晰,易区分识别,植被指数提取结果与对比数据一致性好,高光谱影像可以快速提取不同植被生态类型,总体精度可达90%以上。“资源一号”02E卫星数据能较好地应用于高原地区植被生态系统的调查与精细分类,具备良好的区域生态系统监测能力。

高光谱影像奇异谱分析特征提取方法:综述与评价

高光谱遥感影像(hyperspectral imagery,HSI)通常包含几十至数百个连续波段,具有图谱合一、光谱连续的特点,能够实现地物的精细分类,被广泛应用农业、林业、城市以及海洋等领域。HSI特征提取是高光谱应用的前提,也是遥感领域的研究热点和前沿课题之一。近年来,奇异谱分析(singular spectrum analysis,SSA)被应用于HSI领域,在光谱特征和空间特征提取方面取得了较好效果,逐渐成为特征提取的一种有效方法。本文首先分析了HSI特征提取的研究进展和存在的问题;其次对SSA方法进行了系统的梳理,分别介绍了光谱域1D-SSA、空间域2D-SSA和光谱-空间组合域SSA 3类方法的作用、效果及优缺点,并在两个公开的HSI数据集和一个高分五号HSI数据上进行了分类效果验证;最后,对SSA特征提取进行了总结,并讨论了未来的研究方向。

Indefinite OCSVM method for object detection in hyperspectral imagery

高斯径向基核函数是基于光谱向量间欧氏距离的度量,对于因光照强度变化而引起的地物光谱变异敏感,当同类地物光谱发生变异时,基于高斯径向基核的高光谱影像地物检测算法的性能下降。为了解决该问题,基于光谱曲线形状相似性描述提出了光谱角度余弦核测度这一非正定核函数,并应用于一种非正定OCSVM方法的高光谱影像地物检测。最后利用两幅高光谱影像进行了实验分析,实验结果证明了本文算法的有效性。

高光谱图像稀疏约束与自编码器特征提取相结合的异常检测方法

高光谱图像的异常检测在军事、农业、勘探、防火等领域具有重要的应用价值。传统的高光谱图像异常检测算法未能有效地挖掘图像光谱的深层特征,而深度学习方法具有良好的提取深层特征信息的能力。由于异常检测问题一般无法获取地物先验信息,因此无监督网络相比于监督网络要更为适用。而现有的基于自编码器的异常检测算法没有对局部信息进行有效利用,导致检测效果受限。针对这一问题,本文提出一种基于稀疏表示约束的自编码器深度特征提取方法。首先通过栈式自编码器得到深层次语义信息;然后利用稀疏表示作为约束与编码器进行有效结合,挖掘了潜在隐藏空间中的特征元素的局部表示特性;最后采用分数傅里叶变换,通过空间-频率表示获得原始光谱与其傅里叶变换的中间域中的特征,进一步增强了背景和异常的光谱区分度,且能有效去除噪声的影响。在Hymap、AVIRIS、ROSIS、HYDICE这4种光谱仪采集的5幅高光谱遥感影像上进行了性能验证,得到的曲线下覆盖面积(area under curve,AUC)分别为0.9905、0.9983、0.9990、0.9928和0.9110,相比于对比算法都有了不同程度的效果提升。结果表明本文方法具有更好的检测精度。

结合珠海一号高光谱影像和XGBoost算法的珠江口滨海湿地分类

由于湿地类别多样且结构复杂,湿地遥感分类工作极具挑战性。本文以珠江口滨海湿地为研究区,基于珠海一号高光谱影像获取的光谱特征、形状特征、纹理特征和指数特征构建优选特征集,采用极端梯度提升(XGBoost)算法和面向对象技术提取湿地类型和空间分布,并对比分析基于支持向量机(SVM)算法和随机森林(RF)算法的湿地分类结果。结果表明:(1)珠海一号高光谱影像能够有效应用于湿地分类,且光谱特征在湿地分类中发挥了重要作用;(2)使用的机器学习算法中XGBoost算法的湿地分类效果最佳,总体精度为87.2%,Kappa系数为0.84;(3)优选的影像特征能够保证更高的湿地类型识别精度,验证了特征筛选有助于提高分类效果。本文发展了一种基于珠海一号高光谱影像和集成学习的大区域湿地类型识别方法,可为湿地资源调查提供有效的技术参考,服务于湿地的保护与开发利用。

联合低秩张量分解与稀疏表示的高光谱异常目标检测算法

异常目标检测是当前高光谱图像处理中的一个研究热点。针对当前异常目标检测算法存在的问题,从解决高光谱图像中含有的背景、异常目标和噪声等相关量出发,利用高光谱图像的空间谱和光谱特性,提出了联合低秩张量分解和稀疏表示的新的高光谱图像异常目标检测算法。该算法首先利用低秩张量分解模型对高光谱进行图像恢复,使图像质量得到提升,从而使得异常目标变得突出,易于进行目标检测;然后,再利用稀疏差异指数进行异常目标检测,得到需要的异常检测结果;最后,利用真实的高光谱图像进行仿真实验,结果表明,新的异常目标检测算法具有检测精度高、虚警率低和鲁棒性好的特点。

基于小波卷积网络的高光谱图像分类

高光谱图像波段多、波段之间关联性强,但其空间纹理和几何信息的表达较弱,传统分类模型存在空间光谱特征提取不充分、计算量大的问题,分类性能有待提高.针对此问题,提出一种基于小波变换的多尺度多分辨率注意力特征融合卷积网络(wavelet transform convolutional attention network,WTCAN),采用小波变换思想对光谱波段进行4次分解,通过层次性提取光谱特征可减少计算量.该网络设计了空间信息提取模块,同时引入金字塔注意力机制,通过设计逆向跳跃连接网络结构利用多尺度获取空间位置特征,增强空间纹理表达能力,可以有效改进传统2D-CNN特征提取尺度单一、忽略空间纹理细节等缺陷.本文对所提出的WTCAN模型分别在不同空间分辨率高光谱数据集Indian Pines(IP)、WHU_Hi_HanChuan(HanChuan)、WHU_Hi_HongHu(HongHu)进行实验,通过对比SVM、2D-CNN、DBMA、DBDA、HybridSN模型效果,WTCAN模型取得较好的分类效果,3个数据集的分类总体精度分别达到了98.41%、99.64%、99.67%,可为高光谱图像的分类研究提供参考依据.

基于深度学习的高光谱影像分类方法研究

针对高光谱影像分类方法精度不足的问题,提出一种基于空间-频谱变换(Spectral-Spatial Transformer,SST)网络的高光谱影像分类方法。首先,将高光谱影像预处理为一维特征向量。然后,设计了具有光谱-空间注意力模块和池化残差模块的SST高光谱影像分类网络。本文所提出的分类方法在Indian Pines数据集和Pavia University数据集上的总体分类精度分别为98.67%和99.87%,表明此方法具有较高的分类精度,为高光谱影像分类及应用提供了一种新方案。

对抗性自动编码网络在高光谱异常检测中的应用

自动编码器(autoencoder,AE)是一种典型的生成模型。由于它具有简单的学习过程、良好的收敛能力和无监督的特性而得到了广泛的应用。AE的目标函数仅是输入输出之间的重构误差。为了提高其性能,提出了对抗性自动编码器(adversarial autoencoder,AAE),可以为原始的AE网络提供变分推理输出。本文回顾有关无监督和半监督的AAE模型在高光谱异常检测(hyperspectral anomaly detection,HAD)中的应用。除了在隐层空间中使用对抗性学习外,还可以通过在编码器的输入和解码器的输出之间添加对抗性学习来提高AAE的性能;通过这种方式,改进后的AAE网络可以更专注于学习数据分布而不仅是点对点的数值重建。试验结果表明,利用这些深度学习模型完成HAD任务的想法超越了传统HAD方法的概念,显著提高了检测性能。

应用稀疏非负矩阵分解聚类实现高光谱影像波段的优化选择

针对高光谱影像数据高维性、高度相关性和冗余性等特点,提出应用稀疏非负矩阵分解聚类实现高光谱影像波段的优化选择。通过稀疏非负矩阵分解方法对高光谱影像进行稀疏化表示,同时顾及其可聚类的特性,在保留所选波段物理意义的基础上,得到波段选择后的高光谱影像降维数据。通过该方法对PHI-3高光谱影像进行波段选择的试验分析,应用聚类特征有效性分析波段聚类结果,并采用波段子集的信息量、相关性和可分性3类评价指标来验证方法的效果。最终,从运行效率和分类精度两方面证明了基于无监督聚类的稀疏非负矩阵分解对高光谱影像的波段选择的实用性。