遥感影像压缩的构像质量评价

本文分析了JPEG2000压缩算法的基本原理,对某地区的数字航空遥感影像进行了压缩试验,通过比较不同压缩比下各种评价指标的变化,来研究JPEG2000压缩算法对重建影像构像质量的影响,评价结果表明压缩比的增加,重建影像灰度平均值、标准方差和信息熵在一定范围内波动;同时,随着压缩比的增加,重建影像纹理越来越粗,视觉效果降低,并且重建影像与原始影像的一致性程度降低,差别越来越大。     

JPEG 2000压缩对遥感影像监督分类精度的影响

遥感图像压缩会影响分类精度,是值得研究的问题。以高分辨率遥感影像(Quick Bird)的监督分类精度评定为尺度,采用ER Mapper软件的JPEG 2000图像压缩模块对图像进行压缩,再在eCognition软件中对这9种压缩比图像进行面向对象的监督分类,生成分类精度报告。通过分析分类精度的变化,研究了JPEG 2000压缩对遥感影像分类的影响程度及其在遥感影像压缩方面的应用潜力。     

高分辨率测绘卫星遥感影像星上压缩质量评价

针对高分七号测绘卫星模拟立体像对星上压缩是否满足测图应用需求的问题,本文从影响影像灰度、纹理、相关性等构像质量特征和DSM产品精度两方面进行影像压缩质量评价实验,开展了多种格网尺寸DSM的提取,通过比较不同压缩比下重建与原始影像生成DSM平均高程误差和高程中误差进行DSM产品精度分析。结果表明,对于星上JPEG-LS压缩算法,压缩比不大于4∶1时,压缩后影像灰度特征、纹理信息保持好,影像相关性大于0.997,重建影像峰值信噪比大于50,影像压缩质量好;随着压缩比的增加,DSM产品精度逐渐降低,压缩比不大于4∶1时,DSM高程中误差小于1 m,满足1∶10 000、1∶5 000数字高程模型高程中误差一级要求。本文相关结论可为高分七号星上压缩指标论证提供参考。     

JPEG压缩对摄影测量点定位精度的影响

对某城区一对1：8000航摄立体数学影像利用Intergraph数字摄影测量工作站上的立体量测软件ISDM进行了手上量测，然后通过用自行开发的GPS辅助光束法区域风平差软件WuACPSGPS的单模型光束法平差精确测定了18个加密点的位置，经过对数字影像采用1到100不同的质量因子的JPEG压缩，获得一组质量各异的压缩影像，从分析重建影像点定位结果的变化入手，探讨了JPEG压缩对摄影测量点定位精的影响。试验且明，失真JPEG压缩对摄影测量点定位精度的影响是显著的，随着压缩比的增大，影像可视化质量逐渐衰减，像点量测精度不断降低，加密点位精度几乎呈线性趋势下降，且高程比平面减的速度要快得多。     

基于改进层次分析法的遥感影像压缩质量评价

遥感影像压缩质量评价是影像压缩中的技术难点,目前遥感影像压缩质量评价多采用单一指标评价,尚缺乏多个评价指标综合评价的研究。将改进的层次分析法引入遥感影像压缩质量评价,对主、客观质量评价方法的多个评价指标综合利用,对基于贝叶斯统计学习的遥感影像压缩编码方法和JPEG 2000两种压缩算法的多种压缩比遥感影像数据进行质量评价。通过结果对比分析,验证了算法的有效性,其评价结果对遥感影像压缩处理定量分析具有重要意义和研究价值。     

基于JPEG2000标准的遥感影像在Web GIS上的应用

基于Internet/Intranet的开放式地理信息系统Web GIS，为人类共享遥感影像这一人类共同的资源，提供了快捷灵活的手段。尤其是1998年以来，在“数字地球”的设想下，遥感影像数据无疑会在未来“数字地球”建设中占有重要地位。但是，海量遥感影像数据和网络有限带宽这对矛盾严重地影响着遥感影像的充分应用。国际标准化组织（ISO）和图像专家联合小组（Joint Photographic Experts Group,JPEG)于1997年提出的JPEG2000图像标准，将会很好地解决这一矛盾。该文将论述基于该标准的遥感影像，在Web GIS上的应用实现及结构。     

基于JPEG2000标准的遥感影像在Web GIS上的应用

基于Internet/Intranet的开放式地理信息系统Web GIS，为人类共享遥感影像这一人类共同的资源，提供了快捷灵活的手段。尤其是1998年以来，在“数字地球”的设想下，遥感影像数据无疑会在未来“数字地球”建设中占有重要地位。但是，海量遥感影像数据和网络有限带宽这对矛盾严重地影响着遥感影像的充分应用。国际标准化组织（ISO）和图像专家联合小组（Joint Photographic Experts Group,JPEG)于1997年提出的JPEG2000图像标准，将会很好地解决这一矛盾。该文将论述基于该标准的遥感影像，在Web GIS上的应用实现及结构。     

硝酸片基航片数字化存贮系统

本文根据以有损压缩方法保存硝酸片基航片的技术方案,提出了用直方图分析及原始影像和重建影像之间灰度值的均方根误差与均方根信噪比分析的方法衡理重建影像的信息损失,从而确定了合理的压缩比;同时,用摄影测量的方法和最小二乘匹配的算法检测了重建影像的几何精度。此外,本文还对几种不同的压缩方法进行了初步的比较。     

基于视觉掩盖效应的自适应图像压缩算法

通过分析压缩过程中图像失真的产生机制，提出了一种基于视觉掩盖效应的自适应压缩算法。由于图像是一种非平稳信源，算法采用分块小波变换，并根据图像块的纹理复杂度进行自适应分解，以适应图像不同区域的统计特性。与JPEG2000的对比实验表明，该算法在高倍率压缩时可有效地提高解压图像的视觉质量，较好地保留了图像中的细节及微弱信息。     

遥感影像无损压缩编码的实验分析与改进

遥感影像的内容十分复杂，分辨率较高，用于电视图像或其它视尖信号的无损压缩方法很难使遥感影像的无损压缩达到２倍的压缩比。本文提出一种遥感影像的无损压缩方法，用该方法可使大部分遥感影像达到２倍以上的压缩比。最后还对这部分影像用小波分解理论进行分析，得到０这部分影像量的特征。     

Archiving and distribution of 2-D geophysical data using image formats with lossless compression

Certain types of two-dimensional (2-D) numerical remote sensing data can be losslessly and compactly compressed for archiving and distribution using standardized image formats. One common method for archiving and distributing data involves compressing data files using file compression utilities such as gzip and bzip2, which are widely available on UNIX and Linux operating systems. GZIP-compressed files and bzip2-compressed files must first be uncompressed before they can be read by a scientific application (e.g., MATLAB, IDL). Data stored using an image format, on the other hand, can be read directly by a scientific application supporting that format and, therefore, can be stored in compressed form, saving disk space. Moreover, wide use of image formats by data providers and wide support by scientific applications can reduce the need for providers of geophysical data to develop and maintain software customized for each type of dataset and reduce the need for users to develop and maintain or download and install such software. This letter demonstrates the utility of standardized image formats for losslessly compressing, archiving, and distributing 2-D geophysical data by comparing them with the traditional file compression utilities gzip and bzip2 on several types of remote sensing data. The formats studied include TIFF, PNG, lossless JPEG, JPEG-LS, and JPEG2000. PNG and TIFF are widely supported. JPEG2000 and JPEG-LS could become widely supported in the future. It is demonstrated that when the appropriate image format is selected, the compression ratios can be comparable to or better than those resulting from the use of file compression utilities. In particular, PNG, JPEG-LS, and JPEG2000 show promise for the types of data studied.     

Effects of jpeg 2000 compression on automated dsm extraction: evidence from aerial photographs

This paper evaluates the effects of JPEG 2000 compression on automated digital surface model (DSM) extraction, using the area-based matching technique. Two stereopairs of aerial photographs, which have different photo scale, pixel size, and topographic type, are used as the images for the experiments. In the experiments, the DSM generated from the uncompressed image is set as the reference, and the elevation accuracy is computed for a range of compression ratios (2:1 to 100:1). The results show that the employed indices of image quality based on the JPEG 2000 compression are clearly superior to the commonly used JPEG compression technique—especially for high compression ratios. However, the elevation accuracy varies with the compression ratios. Also, JPEG 2000 compression does not have a significant influence on the percentage of the successful matching rate. In addition, a near linear fall-off is observed in extracted DSM accuracy with increasing compression ratios.     

多尺度字典学习的高光谱图像压缩算法

结合小波变换及字典学习提出了一种针对高光谱图像的压缩算法。该算法首先通过小波变换构建多尺度样本集,在小波域使用K-均值奇异值分解(K-SVD)方法学习得到原子尺寸不同的多尺度字典,然后在稀疏表示的过程中,定义一个原子使用频次筛选因子,通过统计局部最优波段稀疏表示时原子使用情况,结合筛选因子对字典原子进行优化筛选,使用精简后的字典对其余波段进行稀疏求解,最后针对不同尺度的表示系数采用自适应的量化编码。实验结果表明,与目前常用的3D-SPIHT和其他的多尺度字典学习算法相比,本文算法在中低比特率下,具有更好的重建性能。     

Fractal compression of satellite images

Fractal geometry provides a means for describing and analysing the complexity of various features present in digital images. In this paper, characteristics of Fractal based compression of satellite data have been tested for Indian Remote Sensing (IRS) images (of different bands and resolution). The fidelity and efficiency of the algorithm and its relationship with spatial complexity of images is also evaluated. Results obtained from fractal compression have been compared with popularly used compression methods such as JPEG 2000, WinRar. The effect of bands and pixel resolution on the compression rate has also been examined. The results from this study show that the fractal based compression method provides higher compression rate while maintaining the information content of RS images to a great extent than that of JPEG. This paper also asserts that information loss due to fractal compression is minimal. It may be concluded that fractal technique has many potential advantages for compression of satellite images.     

Effects of lossy compression on remote sensing image classification of forest areas

Lossy compression is being increasingly used in remote sensing; however, its effects on classification have scarcely been studied. This paper studies the implications of JPEG (JPG) and JPEG 2000 (J2K) lossy compression for image classification of forests in Mediterranean areas. Results explore the impact of the compression on the images themselves as well as on the obtained classification. The results indicate that classifications made with previously compressed radiometrically corrected images and topoclimatic variables are not negatively affected by compression, even at quite high compression ratios. Indeed, JPG compression can be applied to images at a compression ratio (CR, ratio between the size of the original file and the size of the compressed file) of 10:1 or even 20:1 (for both JPG and J2K). Nevertheless, the fragmentation of the study area must be taken into account: in less fragmented zones, high CR are possible for both JPG and J2K, but in fragmented zones, JPG is not advisable, and when J2K is used, only a medium CR is recommended (3.33:1 to 5:1). Taking into account that J2K produces fewer artefacts at higher CR, the study not only contributes with optimum CR recommendations, but also found that the J2K compression standard (ISO 15444-1) is better than the JPG (ISO 10918-1) when applied to image classification. Although J2K is computationally more expensive, this is no longer a critical issue with current computer technology.     

基于FFT的星载SAR复数图像压缩及其码率控制算法

分析了成像后的星载SAR复数图像压缩的必要性及复数图像特点, 对已有压缩算法做了简单分析。在此基础上, 提出一种基于FFT变换和加权量化的星载SAR复数图像压缩算法, 同时建立了适合SAR复数图像压缩的码率控制模型, 提出一种精确码率控制方法。实验结果表明, 以幅值PSNR和平均结构相似度以及平均相位误差为性能指标, 提出的SAR复数图像压缩算法优于现有压缩算法(JPEG2000、H.264等); 同时, 提出的码率控制算法能够实现精确码率控制。     

An oracle-based data management method for large database in CyberCity GIS

An Oracle8i-based approach is proposed to manage the integrated databases of large CyberCity. This approach consists of three schemes: ? a special R+-tree index is designed to accelerate spatial retrieving, in which the bounding boxes of local regions have no intersection and all leaf nodes of the R+-tree (geometry records) have no repetition; ∪ different data compression algorithms are adopted to compress the digital elevation models, 3D vector models and images, such as LZ77 lossless compression algorithm for compression of vector data and JPEG compression algorithms for texture images; ? in order to communicate with Oracle8i database, a CyberCity GIS spatial database engine (SDE) is designed. On the basis of this SDE prototype a case study is done.