关于多光谱和高光谱影像的纹理问题   总被引：5，自引：5，他引：5  

舒宁 《武汉大学学报(信息科学版)》2004,29(4):292-295

提出了一种新的纹理概念 ,指出纹理是地物目标光谱空间到二维投影空间的映射模式 ,以表述多波段影像或高光谱影像的纹理 ,并蕴含了单波段或黑白影像纹理概念。同时 ,提出了实现空间映射的几种编码方式 ,即基于光谱相似性分析的编码、基于光谱空间密度分析的编码、以影像主成份分析为基础的编码、空间相关性的编码等五种方法。  相似文献   

豫北一次飑线天气过程分析   总被引：1，自引：7，他引：1  

王军  周官辉  杜滨鹤  孙日丁  邢用书  芦阿咪  孙玉巧 《气象》2002,28(11):37-41

利用红外云图及对流层上层（300hPa）常规资料，对2001年6月18日发生在河南省鹤壁、安阳地区的飑线天气过程进行诊断分析。结果表明：由于纬向型内蒙古低涡在东移、南压过程中转为经向型，致使高空强冷平流南下豫北，增强了豫北气层的不稳定性；低层舌状高假相当位温的流入，使低层增温、增湿，形成位势不稳定层结；高空低涡西南侧的正涡度平流和郑州、刑台之间的风速切变，为强对流天气的发生提供了动力条件。  相似文献   

一次大降水天气过程的特征分析     

屈梅 《沙漠与绿洲气象(新疆气象)》2002,25(4):6-8

对巴州地区一次大范围的强降水、冰雹天气作了分析，重点从环流形势、不稳定条件、卫星云图等方面阐明了形成大范围降水的有利条件。指出卫星云图可以提供对中小尺度天气系统的识别和监测，直观反映出大降水，尤其是冰雹的落区，最后，通过对比分析，证明T106产品在预报中的准确性较高，有一定的参考价值。  相似文献   

塔里木盆地一次特大暴雨过程的分析   总被引：2，自引：0，他引：2  

阿不里米提·塔西  王旭 《沙漠与绿洲气象(新疆气象)》2002,25(1):12-14

对1995年9月3－7日塔里木盆地特大暴雨的发生条件进行了诊断分析，用卫星红外云图的云顶黑体温度揭示出青藏高原对流单体北上与低涡云系结合造成和田地区特大暴雨。  相似文献   

SAR影像几何校正   总被引：21，自引：5，他引：21  

张永红  林宗坚  张继贤  甘梦龙 《测绘学报》2002,31(2):134-138

SAR影像的几何校正是阻碍其应用的瓶颈问题，目前所用的方法都有其局限性。介绍描述SAR构像几何的坐标系统及距离－多普勒方程，同时，介绍卫星轨道及描述卫星轨道的参数。为提高几何校正的精度，提出一种由几个离散点的值内插整个弧段上卫星状态向量的轨道模拟算法。在此基础上，给出利用DEM进行SAR影像几何校正的方法。该方法以时间参数为自变量，迭代解算距离－多普勒方程，计算DEM中点每一点对应的影像坐标，最后进行了实验与讨论。  相似文献   

Large-scale urban functional zone mapping by integrating remote sensing images and open social data     

Shouji Du  Bo Liu  Xiuyuan Zhang  Zhijia Zheng 《地理信息系统科学与遥感》2020,57(3):411-430

ABSTRACT

Urban functional zones (UFZs) are important for urban sustainability and urban planning and management, but UFZ maps are rarely available and up-to-date in developing countries due to frequent economic and human activities and rapid changes in UFZs. Current methods have focused on mapping UFZs in a small area with either remote sensing images or open social data, but large-scale UFZ mapping integrating these two types of data is still not be applied. In this study, a novel approach to mapping large-scale UFZs by integrating remote sensing images (RSIs) and open social data is proposed. First, a context-enabled image segmentation method is improved to generate UFZ units by incorporating road vectors. Second, the segmented UFZs are classified by coupling Latent Dirichlet Allocation (LDA) and Support Vector Machine (SVM). In the classification framework, physical features from RSIs and social attributes from POI (Point of Interest) data are integrated. A case study of Beijing was performed to evaluate the proposed method, and an overall accuracy of 85.9% was achieved. The experimental results demonstrate that the presented method can provide fine-grained UFZs, and the fusion strategy of RSIs and POI data can distinguish urban functions accurately. The proposed method appears to be promising and practical for large-scale UFZ mapping.  相似文献   

改进的OPTA算法在遥感影像细化中的应用     

李二森  张保明  郭海涛  周晓明  初艳锋  陈科 《测绘科学》2008,33(6):194-195

在分析和研究快速细化算法和OPTA细化算法基础上,针对快速细化算法细化不彻底和OPTA算法模板设计的缺点提出了对OPTA细化算法的改进,设计了新的细化算法模板。经过实验证明改进的OPTA细化算法能够满足细化的基本要求,既保证了细化结果线条的单像素宽,又保持了原有图像线条的连通性,同时线条细节特征没有丢失,使细化结果得到了较大改善。  相似文献   

球形全景影像核线方程推导及其应用     

刘帅  陈军  孙敏  赵伶俐 《地球信息科学学报》2015,17(3):274-280

核线约束是影像在数字摄影测量中的一项核心技术,可限制同名像点的搜索范围,显著提高计算效率和可靠性。目前,核线约束在传统中心投影影像与卫星扫描影像上取得了广泛的应用,而全景影像具有不同的几何模型,核线模型的推导与应用存在很大的难度。以往实现全景三维重建方法大多通过不同方位影像,应用大量的控制点,结合光束法平差以实现构筑物三维重构,缺乏球形全景核线数学方程的推导及应用。鉴此,本文通过对球形全景影像的投影几何研究,基于共面方程建立该类影像的核线几何模型,推导出数学方程及其特性,为核线在球形全景影像中的应用提供了理论基础,实验表明该球形全景核线方程的正确性与可行性。  相似文献   

Computation of three-phase capillary entry pressures and arc menisci configurations in pore geometries from 2D rock images: A combinatorial approach     

《Advances in water resources》2014

We present a semi-analytical, combinatorial approach to compute three-phase capillary entry pressures for gas invasion into pore throats with constant cross-sections of arbitrary shapes that are occupied by oil and/or water. For a specific set of three-phase capillary pressures, geometrically allowed gas/oil, oil/water and gas/water arc menisci are determined by moving two circles in opposite directions along the pore/solid boundary for each fluid pair such that the contact angle is defined at the front circular arcs. Intersections of the two circles determine the geometrically allowed arc menisci for each fluid pair. The resulting interfaces are combined systematically to allow for all geometrically possible three-phase configuration changes. The three-phase extension of the Mayer and Stowe – Princen method is adopted to calculate capillary entry pressures for all determined configuration candidates, from which the most favorable gas invasion configuration is determined. The model is validated by comparing computed three-phase capillary entry pressures and corresponding fluid configurations with analytical solutions in idealized triangular star-shaped pores. It is demonstrated that the model accounts for all scenarios that have been analyzed previously in these shapes. Finally, three-phase capillary entry pressures and associated fluid configurations are computed in throat cross-sections extracted from segmented SEM images of Bentheim sandstone. The computed gas/oil capillary entry pressures account for the expected dependence of oil/water capillary pressure in spreading and non-spreading fluid systems at the considered wetting conditions. Because these geometries are irregular and include constrictions, we introduce three-phase displacements that have not been identified previously in pore-network models that are based on idealized pore shapes. However, in the limited number of pore geometries considered in this work, we find that the favorable displacements are not generically different from those already encountered in network models previously, except that the size and shape of oil layers that are surrounded by gas and water are described more realistically. The significance of the results for describing oil connectivity in porous media accurately can only be evaluated by including throats with more complex cross-sections in three-phase pore-network models.  相似文献   

新虚拟单能量图像对早期胃癌的诊断价值     

诗涔  ;张欢  ;闫静  ;刘欢欢  ;潘自来  ;严福华 《CT理论与应用研究》2014,(4):535-540

目的：探讨新虚拟单能量图像在早期胃癌中的应用价值。方法：回顾性分析29例在双源CT行腹部双期双能量增强扫描的早期胃癌病人,并经手术证实病理资料。采用双源CT后处理工作站（Dual energy Mono＋,syngo IPIPE,Siemens）使用100和Sn 140kV图像产生40keV、60keV、80keV三组新虚拟单能量图像（AMEIs）,并与常规120kVp图像（PEIs）对照,比较各组对早期胃癌的检出率及CNR差异。结果：AMEIs 40keV组具有最高检出率（86.21%）,但与PEIs组无统计学差异（P=0.062）。AMEIs 40keV组动脉期CNR及门静脉期CNR均明显高于其他各组（P均〈0.05）。结论：双源CT新40keV单能量图像可提高早期胃癌CNR,有利于EGC的检出。  相似文献