Extended Attribute Profiles (EAPs), which are obtained by applying morphological attribute filters to an image in a multilevel architecture, can be used for the characterization of the spatial characteristics of objects in a scene. EAPs have proved to be discriminant features when considered for thematic classification in remote sensing applications especially when dealing with very high resolution images. Altimeter data (such as LiDAR) can provide important information, which being complementary to the spectral one can be valuable for a better characterization of the surveyed scene. In this paper, we propose a technique performing a classification of the features extracted with EAPs computed on both optical and LiDAR images, leading to a fusion of the spectral, spatial and elevation data. The experiments were carried out on LiDAR data along either with a hyperspectral and a multispectral image acquired on a rural and urban area of the city of Trento (Italy), respectively. The classification accuracies obtained pointed out the effectiveness of the features extracted by EAPs on both optical and LiDAR data for classification.

This paper proposes an edge-constrained Markov random field (EC-MRF) method for accurate land cover classification over urban areas using hyperspectral image and LiDAR data. EC-MRF adopts a probabilistic support vector machine for pixel-wise classification of hyperspectral and LiDAR data, while MRF performs as a postprocessing regularizer for spatial smoothness. LiDAR data improve both pixel-wise classification and postprocessing result during an EC-MRF procedure. A variable weighting coefficient, constrained by a combined edge extracted from both hyperspectral and LiDAR data, is introduced for the MRF regularizer to avoid oversmoothness and to preserve class boundaries. The EC-MRF approach is evaluated using synthetic and real data, and results indicate that it is more effective than four similar advanced methods for the classification of hyperspectral and LiDAR data.

Incorporating disparate features from multiple sources can provide valuable diverse information for remote sensing data analysis. However, multisource remote sensing data require large quantities of labeled data to train robust supervised classifiers, which are often difficult and expensive to acquire. A mixture-of-kernel approach can facilitate the construction of an effective formulation for acquiring useful samples via active learning (AL). In this paper, we propose an ensemble multiple kernel active learning (EnsembleMKL-AL) framework that incorporates different types of features extracted from multisensor remote sensing data (hyperspectral imagery and LiDAR data) for robust classification. An ensemble of probabilistic multiple kernel classifiers is embedded into a maximum disagreement-based AL system, which adaptively optimizes the kernel for each source during the AL process. At the end of each learning step, a decision fusion strategy is implemented to make a final decision based on the probabilistic outputs. The proposed framework is tested in a multisource environment, including different types of features extracted from hyperspectral and LiDAR data. The experimental results validate the efficacy of the proposed approach. In addition, we demonstrate that using ensemble classifiers and a large number of disparate but relevant features can further improve the performance of an AL-based classification approach.

A novel multiple-kernel learning (MKL) model is proposed for urban classification to integrate heterogeneous features (HF-MKL) from two data sources, i.e., spectral images and LiDAR data. The features include spectral, spatial, and elevation attributes of urban objects from the two data sources. With these heterogeneous features (HFs), the new MKL model is designed to carry out feature fusion that is embedded in classification. First, Gaussian kernels with different bandwidths are used to measure the similarity of samples on each feature at different scales. Then, these multiscale kernels with different features are integrated using a linear combination. In the combination, the weights of the kernels with different features are determined by finding a projection based on the maximum variance. This way, the discriminative ability of the HFs is exploited at different scales and is also integrated to generate an optimal combined kernel. Finally, the optimization of the conventional support vector machine with this kernel is performed to construct a more effective classifier. Experiments are conducted on two real data sets, and the experimental results show that the HF-MKL model achieves the best performance in terms of classification accuracies in integrating the HFs for classification when compared with several state-of-the-art algorithms.

Nowadays, we have diverse sensor technologies and image processing algorithms that allow one to measure different aspects of objects on the Earth [e.g., spectral characteristics in hyperspectral images (HSIs), height in light detection and ranging (LiDAR) data, and geometry in image processing technologies, such as morphological profiles (MPs)]. It is clear that no single technology can be sufficient for a reliable classification, but combining many of them can lead to problems such as the curse of dimensionality, excessive computation time, and so on. Applying feature reduction techniques on all the features together is not good either, because it does not take into account the differences in structure of the feature spaces. Decision fusion, on the other hand, has difficulties with modeling correlations between the different data sources. In this letter, we propose a generalized graph-based fusion method to couple dimension reduction and feature fusion of the spectral information (of the original HSI) and MPs (built on both HS and LiDAR data). In the proposed method, the edges of the fusion graph are weighted by the distance between the stacked feature points. This yields a clear improvement over an older approach with binary edges in the fusion graph. Experimental results on real HSI and LiDAR data demonstrate effectiveness of the proposed method both visually and quantitatively.

Interest in the joint use of different data from multiple sensors has been increased for classification applications. This is because the fusion of different information can produce a better understanding of the observed site. In this field of study, the fusion of light detection and ranging (LIDAR) and passive optical remote sensing data for classification of land cover has attracted much attention. This paper addressed the use of a combination of hyperspectral (HS) and LIDAR data for land cover classification. HS images provide a detailed description of the spectral signatures of classes, whereas LIDAR data give detailed information about the height but no information for the spectral signatures. This paper presents a multiple fuzzy classifier system for fusion of HS and LIDAR data. The system is based on the fuzzy K-nearest neighbor (KNN) classification of two data sets after application of feature grouping on them. Then a fuzzy decision fusion method is applied to fuse the results of fuzzy KNN classifiers. An experiment was carried out on the classification of HS and LIDAR data from Houston, USA. The proposed fuzzy classifier ensemble system for HS and LIDAR data provide interesting conclusions on the effectiveness and potentials of the joint use of these two data. Fuzzy classifier fusion on these two data sets improves the classification results when compared with independent single fuzzy classifiers on each data set. The fuzzy proposed method represented the best accuracy with a gain in overall accuracy of 93%.

Regarding to the limitations and benefits of remote sensing sensors, fusion of remote sensing data from multiple sensors such as hyperspectral and LIDAR (light detection and ranging) is effective at land cover classification. Hyperspectral images (HSI) provide a detailed description of the spectral signatures of classes, whereas LIDAR data give height detailed information. However, because of the more complexities and mixed information in LIDAR and HSI, traditional crisp classification methods could not be more efficient. In this situation, fuzzy classifiers could deliver more satisfactory results than crisp classification approaches. Also, referring to the limitation of single classifiers, multiple classifier system (MCS) may exhibit better performance in the field of multi-sensor fusion. This paper presents a fuzzy multiple classifier system for fusions of HSI and LIDAR data based on decision template (DT). After feature extraction and feature selection on each data, all selected features of both data are applied on a cube. Then classifications were performed by fuzzy k-nearest neighbour (FKNN) and fuzzy maximum likelihood (FML) on cube of features. Finally, a fuzzy decision fusion method is utilized to fuse the results of fuzzy classifiers. In order to assess fuzzy MCS proposed method, a crisp MCS based on support vector machine (SVM), KNN and maximum likelihood (ML) as crisp classifiers and naive Bayes (NB) as crisp classifier fusion method is applied on selected cube feature. A co-registered HSI and LIDAR data set from Houston of USA was available to examine the effect of proposed MCSs. Fuzzy MCS on HSI and LIDAR data provide interesting conclusions on the effectiveness and potentialities of the joint use of these two data.

Several studies suggest that the use of geometric features along with spectral information improves the classification and visualization quality of hyperspectral imagery. These studies normally make use of spatial neighborhoods of hyperspectral pixels for extracting these geometric features. In this work, we merge point cloud Light Detection and Ranging (LiDAR) data and hyperspectral imagery (HSI) into a single sparse modeling pipeline for subpixel mapping and classification. The model accounts for material variability and noise by using learned dictionaries that act as spectral endmembers. Additionally, the estimated abundances are influenced by the LiDAR point cloud density, particularly helpful in spectral mixtures involving partial occlusions and illumination changes caused by elevation differences. We demonstrate the advantages of the proposed algorithm with co-registered LiDAR-HSI data.

In this paper, we propose an adaptive locality weighted multisource joint sparse representation classification (ALWMJ-SRC) model for the classification of multisource remote sensing data. Although the notion of multitask joint sparsity has been recently developed for data fusion and has shown to be effective for various applications, in this paper, we suggest that there are important limitations stemming from the assumptions in such a framework. We propose a formulation that is inspired by this approach yet addresses some of the key shortcomings (e.g., uniform weights and unstable estimation of coefficients), resulting in a more robust formulation for data fusion. Specifically, we impose an adaptive locality weight to constrain the sparse coefficients, which not only considers the locality information between the test sample and the atoms in the dictionary but also helps ensure that the coefficients are adaptively penalized, reducing estimation bias. The adaptive locality weight is calculated for each source, which ensures that complementary information is employed from different sources for fusion. The optimization problem is solved using an alternating-direction-methods-of-multipliers formulation. In addition, the proposed algorithm is extended to the kernel space. The efficacy of the proposed algorithm is validated via experiments for two fusion scenarios-spectral-spatial classification and hyperspectral-LiDAR sensor fusion. The experimental results demonstrate that ALWMJ-SRC consistently performs better than state-of-the-art classification approaches.

Landscape visual quality is an important factor associated with daily experiences and influences our quality of life. In this work, the authors present a method of fusing airborne hyperspectral and mapping light detection and ranging (LiDAR) data for landscape visual quality assessment. From the fused hyperspectral and LiDAR data, classification and depth images at any location can be obtained, enabling physical features such as land-cover properties and openness to be quantified. The relationship between physical features and human landscape preferences is learned using least absolute shrinkage and selection operator (LASSO) regression. The proposed method is applied to the hyperspectral and LiDAR datasets provided for the 2013 IEEE GRSS Data Fusion Contest. The results showed that the proposed method successfully learned a human perception model that enables the prediction of landscape visual quality at any viewpoint for a given demographic used for training. This work is expected to contribute to automatic landscape assessment and optimal spatial planning using remote sensing data.

本文利用高光谱遥感影像和机载 LiDAR 数据融合来重点提取城市的房屋和树木目标。首先通过机载LiDAR 点云数据提取数字地面模型（Digital Surface Model，DSM）和数字地形模型（Digital Terrain Model，DTM），进一步差值计算得到 nDSM （normalized Digital Surface Model）。利用高光谱影像计算归一化植被指数（Normalized Difference Vegetation Index，NDVI），采用主成分分析法（Principal Component Analysis，PCA）进行去噪和降维处理。结合 nDSM 和 NDVI 图像，采用面向对象的特征提取方法实现研究区内大型商用房屋的提取。对 PCA 图像和 nDSM 图像进行融合，然后采用最大似然分类（Maximum Likelihood Classification，MLC）方法进行监督分类，实现民用房屋和树木的提取。本文研究结果显示：商用房屋的正确提取率达到89．53％；MLC 方法对融合图像分类的总体精度为84．00％，Kappa 系数为82．86。

介绍了"黑河流域生态—水文过程综合遥感观测联合试验"的背景、科学目标、试验组成和试验方案。试验的总体目标是显著提升对流域生态和水文过程的观测能力,建立国际领先的流域观测系统,提高遥感在流域生态—水文集成研究和水资源管理中的应用能力。由基础试验、专题试验、应用试验、产品与方法研究和信息系统组成。其中,①基础试验:搭载微波辐射计、成像光谱仪、热像仪、激光雷达等航空遥感设备,开展一系列关键生态和水文参量的观测;发展遥感正向模型及反演和估算方法。形成覆盖全流域的水文气象综合观测网,为流域生态—水文模型研究提供更有代表性的模型参数、驱动数据及更高精度的验证数据。构建无线传感器网络,度量生态水文模型所需的若干关键的驱动、参数和模型状态的空间异质性。开展航空遥感定标和地基遥感试验。依托传感器网络,并辅之以地面同步和加密观测,开展遥感产品真实性检验。②专题试验:开展"非均匀下垫面多尺度地表蒸散发观测试验",采用密集的涡动相关仪、大孔径闪烁仪与自动气象站的观测矩阵,为揭示地表蒸散发的空间异质性,实现非均匀下垫面地表蒸散发的尺度扩展,发展和验证蒸散发模型提供基础数据。③应用试验:在流域上、中、下游分别开展针对积雪和冻土水文、灌溉水平衡和作物生长、生态耗水的综合观测试验,将观测数据和遥感产品用于上游分布式水文模型、中游地表水—地下水—农作物生长耦合模型、下游生态耗水模型,通过实证研究提升遥感在流域生态—水文集成研究和水资源管理中的应用能力。加强试验将在2012年5月起按中游、上游、下游的顺序展开,全流域持续观测期为2013—2015年。在各类试验的支持下,开展全流域生态—水文关键参量遥感产品生产,发展尺度转换方法,建立多源遥感数据同化系统。

In this paper, Zhangye Oasis, a famous agricultural base located in the alluvion of Heihe River in Northwest China is selected as study area. Landscape maps are compiled based on the landuse maps interpreted from Landsat TM images in 1995. Various landscape metrics are calculated by using the landscape structure analysis software-FRAGSTATS Version 3 at class and landscape levels, including total area of landscape, percentage of landscape types, patch density, edge density, largest patch indices, perimeter-area fractal dimension, interspersion & juxtaposition index, aggregation index, percentage of like adjacencies, patch cohesion index, Shannon diversity index, Shannon evenness index, patch richness and contagion. The results indicate that: desert, grassland, field and gobi are the major components in the oasis. The landscape patterns of the oasis are heterogeneous mosaics embedded in desert and gobi landscape matrix. Patches number of rural villages is the largest, which indicates the important influence of human beings. They are scattered in the whole landscapes and the cohesion indices is the lowest, because they are unconnected each other. The shape of bare rock and grassland are the most complex, which reflected the human-induced fragmentation of these types. In addition, the better connection of dry field, Gobi and bare rock indicate that the energy and mass can be transferred within the same types easily. At last, the caution of scale dependent of grid and classification was discussed.

随着模式识别、机器学习、遥感技术等相关学科领域的发展,高光谱遥感影像分类研究取得快速进展。本文系统总结和评述了当前高光谱遥感影像分类的相关研究进展,在总结分类策略的基础上,重点从以核方法为代表的新型分类器设计、特征挖掘、空间-光谱分类、基于主动学习和半监督学习的分类、基于稀疏表达的分类、多分类器集成六个方面对高光谱影像像素级分类最新研究进行了综述。针对今后的研究方向,指出高光谱遥感影像分类一方面要适应大数据、智能化高光谱对地观测的发展前沿,继续引入机器学习领域的新理论、新方法,综合利用多源遥感数据、多维特征空间互补的优势,提高分类精度、分类器泛化能力和自动化程度;另一方面要关注高光谱遥感应用的需求,突出高光谱遥感记录精细光谱特征的优势,针对应用需求发展有效的分类方法。