基于PCA和NSCT的多光谱图像和全色图像的融合

研究了主分量分析（PCA）和非下采样Contourlet变换（NSCT）,提出一种新的多光谱图像和全色图像的融合算法。该方法对多光谱图像进行PCA变换,对所得的第一主分量（PC1）以及全色图像进行NSCT变换。对二者的低频近似系数再次进行PCA变换以寻求多光谱信息和空间信息的平衡;对于高频细节系数,通过结构相似性指标（SSIM）和局部Sobel梯度进行融合,进一步提高空间信息量;经过逆NSCT和逆PCA变换得到融合图像。实验结果表明,提出的方法在增强融合图像空间细节表现能力的同时,尽可能地保留了多光谱图像的光谱信息,优于传统的基于IHS、PCA、小波变换和Contourlet变换的融合方法,是有效可行的。     

形态学滤波和改进PCNN的NSST域多光谱与全色图像融合

目的 全色图像的空间细节信息增强和多光谱图像的光谱信息保持通常是相互矛盾的,如何能够在这对矛盾中实现最佳融合效果一直以来都是遥感图像融合领域的研究热点与难点。为了有效结合光谱信息与空间细节信息,进一步改善多光谱与全色图像的融合质量,提出一种形态学滤波和改进脉冲耦合神经网络（PCNN）的非下采样剪切波变换（NSST）域多光谱与全色图像融合方法。方法 该方法首先分别对多光谱和全色图像进行非下采样剪切波变换;对二者的低频分量采用形态学滤波和高通调制框架（HPM）进行融合,将全色图像低频子带的细节信息注入到多光谱图像低频子带中得到融合后的低频子带;对二者的高频分量则采用改进脉冲耦合神经网络的方法进行融合,进一步增强融合图像中的空间细节信息;最后通过NSST逆变换得到融合图像。结果 仿真实验表明,本文方法得到的融合图像细节信息清晰且光谱保真度高,视觉效果上优势明显,且各项评价指标与其他方法相比整体上较优。相比于5种方法中3组融合结果各指标平均值中的最优值,清晰度和空间频率分别比NSCT-PCNN方法提高0.5%和1.0%,光谱扭曲度比NSST-PCNN方法降低4.2%,相关系数比NSST-PCNN方法提高1.4%,信息熵仅比NSST-PCNN方法低0.08%。相关系数和光谱扭曲度两项指标的评价结果表明本文方法相比于其他5种方法能够更好地保持光谱信息,清晰度和空间频率两项指标的评价结果则展示了本文方法具有优于其他对比方法的空间细节注入能力,信息熵指标虽不是最优值,但与最优值非常接近。结论 分析视觉效果及各项客观评价指标可以看出,本文方法在提高融合图像空间分辨率的同时,很好地保持了光谱信息。综合来看,本文方法在主观与客观方面均具有优于亮度色调饱和度（IHS）法、主成分分析（PCA）法、基于非负矩阵分解（CNMF）、基于非下采样轮廓波变换和脉冲耦合神经网络（NSCT-PCNN）以及基于非下采样剪切波变换和脉冲耦合神经网络（NSST-PCNN）5种经典及现有流行方法的融合效果。     

Estimation of incident solar radiation on the ground from multispectral satellite sensor imagery

A simple and fast, physically based method for the estimation of global radiation is presented. It is applicable for clear‐sky multispectral satellite sensor imagery with channels at least in the VNIR region and works without the need for additional ground data. The atmospheric influence is taken into account using look‐up tables based on standard atmospheres from the MODTRAN code. The algorithm was tested with a time series of nine Landsat‐7 ETM+ scenes of a region in north‐eastern Germany. Remotely sensed global radiation is in close agreement with in situ measurements of the German Meteorological Service as indicated by RMS deviations of 20–24 W m^?2 depending on the bands and atmospheric parameterization employed. The image‐derived global radiation at this level of accuracy is a useful supplement for studies in landscape ecology and related fields, for example as input for regional modelling of evapotranspiration.     

Fusion and registration of THEOS multispectral and panchromatic images

This article presents a new method for the fusion and registration of THEOS (Thailand Earth Observation Satellite) multispectral and panchromatic images in a single step. In the usual procedure, fusion is an independent process separated from the registration process. However, both image registration and fusion can be formulated as estimation problems. Hence, the registration parameters can be automatically tuned so that both fusion and registration can be optimized simultaneously. Here, we concentrate on the relationship between low-resolution multispectral and high-resolution panchromatic imagery. The proposed technique is based on a statistical framework. It employs the maximum a posteriori (MAP) criterion to jointly solve the fusion and registration problem. Here, the MAP criterion selects the most likely fine resolution multispectral and mapping parameter based on observed coarse resolution multispectral and fine resolution panchromatic images. The Metropolis algorithm was employed as the optimization algorithm to jointly determine the optimum fine resolution multispectral image and mapping parameters. In this work, a closed-form solution that can find the fused multispectral image with correcting registration is also derived. In our experiment, a THEOS multispectral image with high spectral resolution and a THEOS panchromatic image with high spatial resolution are combined to produce a multispectral image with high spectral and spatial resolution. The results of our experiment show that the quality of fused images derived directly from misaligned image pairs without registration error correction can be very poor (blurred and containing few sharp edges). However, with the ability to jointly fuse and register an image pair, the quality of the resulting fused images derived from our proposed algorithm is significantly improved, and, in the simulated cases, the fused images are very similar to the original high resolution multispectral images, regardless of the initial registration errors.     

地球观测1号高光谱与全色图像融合的最佳方法

受制于成像原理及制造技术等因素,航天高光谱遥感图像的空间分辨率相对较低,为此提出将高光谱图像与高空间分辨率图像进行融合处理,设计最佳的增强高光谱遥感图像空间分辨率的融合算法。针对地球观测1号(EO-1)Hyperion高光谱图像和高级陆地成像仪（ALI）全色波段图像的特点,从9种具体遥感图像融合算法中选用4种融合算法开展山区与城市的数据融合实验,即Gram-Schmidt光谱锐化融合法、平滑调节滤波(SFIM)变换融合法、加权平均法（WAM）融合法和小波变换（WT）融合法,并分别从定性、定量和分类精度三方面对这些方法的融合效果进行综合评价与对比分析,从而确定适合EO-1高光谱与全色图像融合的最佳方法。实验结果显示：从图像融合效果看,在所采用的4种融合方法中,Gram-Schmidt光谱锐化融合法的效果最好;从图像分类效果看,基于融合图像的分类效果要优于基于源图像的分类效果。理论分析与实验结果均表明：Gram-Schmidt光谱锐化融合法是一种较为理想的高光谱与高空间分辨率遥感图像的融合算法,为提高高光谱遥感图像的清晰度、可靠性及图像的地物识别和分类的准确性提供有力的支持。     

Fusion of multispectral and panchromatic images based on support value transform and adaptive principal component analysis

In this paper we combined the projection-substitution with ARSIS (French acronym for “Amélioration de la Résolution Spatiale par Injection de Structures”, i.e., Improving Spatial Resolution by Structure Injection) concept assumption for fusion of panchromatic (PAN) and multispectral (MS) images. Firstly support value filter (SVF) is used to establish a new multiscale model (MSM), support vector transform (SVT), and adaptive principal component analysis (APCA) is then employed to select the principal components of MS images by means of a statistical measure of the correlation between MS and PAN images; secondly, a local approach is used to check whether a structure should appear in the new principal component and PAN high frequency structures are transformed by high resolution interband structure model (HRIBSM) before inserting in the MS modalities. Because SVT is an undecimated, dyadic and aliasing transform with shift-invariant property, the fused image can avoid ringing effects suffered from sampling. Additionally, the ARSIS concept can make full use of the remote sensing physics to reduce the spatial and spectrum distortion in the structure injection. Texture extraction is also employed to avoid the spectral distortion caused by the mistaken injection of low-pass components into the MS images. Experimental results including visual and numerical evaluation also proves the superiority of the proposed method to its counterparts.     

Fourier Series for analysis of temporal sequences of satellite sensor imagery

Fourier Series and the derivative were used in this study for analysing time series of remotely-sensed data. The technique allows fundamental characteristics of time series data to be quantified. In Fourier analysis a function in space or time is broken down into sinusoidal components, or harmonics. The first and second harmonics are a function of the mono or bi-modality of the curve, demonstrated in the study on Global Vegetation Index data classified into typical mono and bi-modal vegetation index zones. The last harmonic explains close to 100 per cent of the variance in the curve. Other important parameters of the time series, such as extreme points and rate of change, can be extracted from the derivative of the Fourier Series. Fourier Series may form a basis for a quantitative approach to the problem of handling temporal sequences of remotely-sensed data.     

Using very high spatial resolution multispectral satellite sensor imagery to monitor refugee camps

Detailed geographic information is a key factor in decision making processes during refugee relief operations. The forthcoming commercial very high spatial resolution (VHSR) satellite sensors will be capable of acquiring multispectral (MS) images at spatial resolutions of 1m (panchromatic) and 4m (multispectral) of refugee camps and their environment. This work demonstrates how refugee camp environment, area and population can be analysed using a VHSR MS satellite sensor image from the Russian KVR-1000 sensor. This image, with a spatial resolution of 3.3m, was used to study Thailand's Site 2 refugee camps, which were established to accommodate Khmer refugees on the Thai-Kampuchean border. At the time of image acquisition, the total population of Site 2's five refugee camps was close to 143000. The VHSR MS image was found to be suitable for mapping the refugee camp environment and area. A statistically significant linear relationship between camp area and population was determined. Accordingly, the study suggests that VHSR MS images in general may be useful for refugee camp planning and management and points toward the utilization of forthcoming commercial VHSR MS satellite sensor images in humanitarian relief operations.     

Visualization and unsupervised classification of changes in multispectral satellite imagery

The statistical techniques of multivariate alteration detection, minimum/maximum autocorrelation factors transformation, expectation maximization and probabilistic label relaxation are combined in a unified scheme to visualize and to classify changes in multispectral satellite data. The methods are demonstrated with an example involving bitemporal LANDSAT TM imagery.     

Fusion of multispectral and panchromatic images via sparse representation and local autoregressive model

In this paper, a novel model-based pan-sharpening method via sparse representation and local autoregressive (AR) model is proposed. To recover the high-resolution multispectral (HRMS) image from the observed images, we impose sparsity prior on the unknown HRMS image in the restoration model. The quality of the recovered HRMS image depends on the employed sparse domain. Hence, a new sparse representation model for the HRMS image is constructed, in which we suppose that the low-frequency and high-frequency components of the HRMS image can be sparsely represented by a spectral dictionary and a spatial-detail dictionary respectively. The spectral dictionary and spatial-detail dictionary are learned from the source images: low-spatial-resolution multispectral (LRMS) image and high-spatial-resolution panchromatic (HRP) image adaptively. Additionally, local autoregressive (AR) model is employed to improve the spatial structure of the HRMS image patch. Firstly, a set of AR model parameters are learned from the PAN image patches. Then, the local spatial structure of a given HRMS image patch is regularized by an AR model with the learned parameters. By solving the l₁ -norm optimization problem, the HRMS image can be well reconstructed. Experiments are carried out on very high-resolution QuickBird and GeoEye-1 images. In the simulated and real experiments, our proposed method demonstrates its good performance in terms of visual analysis and quantitative evaluation.     

Cloud/snow recognition for multispectral satellite imagery based on a multidimensional deep residual network

Cloud/snow recognition technology for multispectral satellite imagery plays an important role in resource investigation, natural disasters, and environmental pollution. Traditional feature based classification methods cannot make full use of the effective features and multispectral optical parameters of satellite imagery; the precision of cloud/snow recognition is not good enough. Although deep convolution neural network (CNN) can extract features effectively, it faces training gradient diffusion and model degradation, which lead to a low accuracy in classification. In order to solve this problem, an improved deep residual network with multidimensional input is proposed for the cloud/snow recognition. The multidimensional deep residual network (M-ResNet) can effectively extract the image features and spectral information of satellite imagery. The multispectral satellite imagery is divided into cloud/snow-free, cloud only, snow only and cloud/snow mixed using the proposed method. The experimental results of HuanJing-1A/1B (HJ-1A/1B) satellite imagery in China show that the M-ResNet performs a good distinction for the four kinds of images. The accuracy of the classification is higher than support vector machine (SVM), random forest, convolution neural networks, and multi-grained cascaded forest (GcForest).     

Speckle filtering in satellite SAR change detection imagery

Repeat-pass Synthetic Aperture Radar (SAR) imagery is useful for change detection. A disadvantage of SAR is the system-inherent speckle noise. This can be reduced by filtering. Various filter types and methods are described in the literature, but not one fits the speckle noise in change detection imagery. A new method is therefore developed in this paper. The new method is based on filtering the logarithmic-scaled ratio of SAR images. Logarithmic scaling changes the multiplicative speckle noise in the ratio-image into additive noise and alters the distribution, which simplifies and optimizes the subsequent filter process. The filter in the new method consists of an additive LLMMSE filter (Kuan et al. 1985), preceded by a structure detection stage for a better contour preserving performance. Testing the new method on a repeat-pass satellite SAR image-set gave an accurate overview of changes compared to a colour-composite of both images, other optical remote sensing images and maps of the same area.     

基于脊波的多光谱和全色图像融合方法研究

应用了双线性插值的矩形阵列到径向阵列的变换算法,给出了一个离散脊波变换的实现方法,将其应用于多光谱图像与全色图像的融合算法中,通过清晰度、灰度方差、信息熵三个方面,将算法结果与小波变换的结果进行了对比,实验结果表明,相对于小波变换而言,脊波变换能更好地处理线和面的奇异性,而且由融合的结果来看,脊波变换得到的结果在清晰度等方面要高于小波变换。     

Unsupervised building detection in complex urban environments from multispectral satellite imagery

A generic algorithm is presented for automatic extraction of buildings and roads from complex urban environments in high-resolution satellite images where the extraction of both object types at the same time enhances the performance. The proposed approach exploits spectral properties in conjunction with spatial properties, both of which actually provide complementary information to each other. First, a high-resolution pansharpened colour image is obtained by merging the high-resolution panchromatic (PAN) and the low-resolution multispectral images yielding a colour image at the resolution of the PAN band. Natural and man-made regions are classified and segmented by the Normalized Difference Vegetation Index (NDVI). Shadow regions are detected by the chromaticity to intensity ratio in the YIQ colour space. After the classification of the vegetation and the shadow areas, the rest of the image consists of man-made areas only. The man-made areas are partitioned by mean shift segmentation where some resulting segments are irrelevant to buildings in terms of shape. These artefacts are eliminated in two steps: First, each segment is thinned using morphological operations and its length is compared to a threshold which is determined according to the empirical length of the buildings. As a result, long segments which most probably represent roads are masked out. Second, the erroneous thin artefacts which are classified by principal component analysis (PCA) are removed. In parallel to PCA, small artefacts are wiped out based on morphological processes as well. The resultant man-made mask image is overlaid on the ground-truth image, where the buildings are previously labelled, for the accuracy assessment of the methodology. The method is applied to Quickbird images (2.4 m multispectral R, G, B, near-infrared (NIR) bands and 0.6 m PAN band) of eight different urban regions, each of which includes different properties of surface objects. The images are extending from simple to complex urban area. The simple image type includes a regular urban area with low density and regular building pattern. The complex image type involves almost all kinds of challenges such as small and large buildings, regions with bare soil, vegetation areas, shadows and so on. Although the performance of the algorithm slightly changes for various urban complexity levels, it performs well for all types of urban areas.     

Wetland mapping by fusion of airborne laser scanning and multi-temporal multispectral satellite imagery

Wetlands play a major role in Europe’s biodiversity. Despite their importance, wetlands are suffering from constant degradation and loss, therefore, they require constant monitoring. This article presents an automatic method for the mapping and monitoring of wetlands based on the fused processing of laser scans and multispectral satellite imagery, with validations and evaluations performed over an area of Lake Balaton in Hungary. Markov Random Field models have already been shown to successfully integrate various image properties in several remote sensing applications. In this article, we propose the multi-layer fusion Markov Random Field model for classifying wetland areas, built into an automatic classification process that combines multi-temporal multispectral images with a wetland classification reference map derived from airborne laser scanning (ALS) data acquired in an earlier year. Using an ALS-based wetland classification map that relied on a limited amount of ground truthing proved to improve the discrimination of land-cover classes with similar spectral characteristics. Based on the produced classifications, we also present an unsupervised method to track temporal changes of wetland areas by comparing the class labellings of different time layers. During the evaluations, the classification model is validated against manually interpreted independent aerial orthoimages. The results show that the proposed fusion model performs better than solely image-based processing, producing a non-supervised/semi-supervised wetland classification accuracy of 81–93% observed over different years.     

Finding satellite sensor imagery by use of the LEDA databank

Abstract

The on-Line Earthnet Data Availability (LEDA) databank is a catalogue of imagery recorded by the sensors onboard the Landsat and TIROS (NOAA 9 and 10) satellites. Traditionally, online catalogues of this type have been searched by information specialists on behalf of the data user, a situation which can lead to delays. The authors feel that the LEDA databank combines the advantages of being both relatively inexpensive and easy to search. Thus the data user can search the databank.     

Using PCA transformation to remove the tenuous cloudiness effect in multispectral satellite sensor images

An algorithm using no external data is proposed for removing the inhomogeneous effect of thin cloudiness and other aerosols on multispectral satellite sensor images such as Landsat Enhanced Thematic Mapper (ETM) images. The method consists of a series of digital processing operations and is based on principal component analysis (PCA). The goal is to generate, for every original band, a new band whose digital number (DN) values are related only to the atmospheric intensity effect. An example is shown and some limitations are discussed.     

Bidimensional Empirical Mode Decomposition for the fusion of multispectral and panchromatic images

Currently available image fusion techniques applied to the merging of fine resolution panchromatic and multispectral images are still not able to minimize colour distortion and maximize spatial detail. In this study, a new fusion method, based on Bidimensional Empirical Mode Decomposition (BEMD), is proposed. Unlike other multiresolution analysis tools, such as the discrete wavelet transform (DWT), which normally examines only horizontal, vertical and diagonal orthonormal details at each decomposed scale, the BEMD produces a fully two‐ dimensional decomposition of the panchromatic and multispectral images, based purely on spatial relationships between the extrema of the image. These are decomposed into a certain level of Intrinsic Mode Functions (IMFs) and residual images with the same number of columns and rows as the original image. In consequence, by injecting all the IMF images from the panchromatic image into the residue of the corresponding multispectral image, the fusion image may be reconstructed. The fusion results are evaluated and compared with other popular methods in terms of both the visual examination and the quantitative assessment of the merged images. Preliminary results show that BEMD is optimal and provides a delicate balance between spectral information preservation and enhancement of spatial detail.     

Texture based feature extraction: Application to burn scar detection in Earth observation satellite sensor imagery

A single band texture-based burn scar identification algorithm incorporating the use of grey level co-occurrence matrices with a low pass filtering technique is described and demonstrated using 1km resolution ATSR-2 imagery of burned savannas in southern Sudan. The algorithm results are compared to those produced by the iterative intensity-based isodata classification technique. The accuracy of each of these methods was evaluated by comparison with 18 m spatial resolution imagery. For a set of 22 sample fire scars of varying area Pearson correlation coefficients of 0.75 and 0.94 were obtained between the burnt area statistics produced with the low-spatial resolution texture and isodata methods respectively and those produced using the high-resolution data. The classification quality, as described by the Kappa ( k ) statistic, produced values of k TEXTURE =0.558 and k ISODATA =0.852. Texture is shown to be an image variable capable of highlighting burned area in low spatial resolution imagery, but the currently tested approach offers no accuracy of quality benefit over the solely intensity-based method.     

A simple method for detection and counting of oil palm trees using high-resolution multispectral satellite imagery

In the past, oil palm density has been determined by manually counting trees every year in oil palm plantations. The measurement of density provides important data related to palm productivity, fertilizer needed, weed control costs in a circle around each tree, labourers needed, and needs for other activities. Manual counting requires many workers and has potential problems related to accuracy. Remote sensing provides a potential approach for counting oil palm trees. The main objective of this study is to build a robust and user-friendly method that will allow oil palm managers to count oil palm trees using a remote sensing technique. The oil palm trees analysed in this study have different ages and densities. QuickBird imagery was applied with the six pansharpening methods and was compared with panchromatic QuickBird imagery. The black and white imagery from a false colour composite of pansharpening imagery was processed in three ways: (1) oil palm tree detection, (2) delineation of the oil palm area using the red band, and (3) counting oil palm trees and accuracy assessment. For oil palm detection, we used several filters that contained a Sobel edge detector; texture analysis co-occurrence; and dilate, erode, high-pass, and opening filters. The results of this study improved upon the accuracy of several previous research studies that had an accuracy of about 90–95%. The results in this study show (1) modified intensity-hue-saturation (IHS) resolution merge is suitable for 16-year-old oil palm trees and have rather high density with 100% accuracy; (2) colour normalized (Brovey) is suitable for 21-year-old oil palm trees and have low density with 99.5% accuracy; (3) subtractive resolution merge is suitable for 15- and 18-year-old oil palm trees and have a rather high density with 99.8% accuracy; (4) PC spectral sharpening with 99.3% accuracy is suitable for 10-year-old oil palm trees and have low density; and (5) for all study object conditions, colour normalized (Brovey) and wavelet resolution merge are two pansharpening methods that are suitable for oil palm tree extraction and counting with 98.9% and 98.4% accuracy, respectively.