云图定量降水估测研究

分析了降水的云图特征。找出了与降水关系密切的云顶温度,云顶温度变量及水汽通道灰度等因子。在此基础上建立了云图定量降水的统计模式,于1998年5～8月投入业务试用,效果较好。     

Derivation of sea surface current field from sequential satellite images of the East China Sea

ThisprojectwassupportedbytheGermanMinistryofScienceandTechnology(BMFTBEO/7103F0016A)andtheStateOceanicAdministration,China.INTRoDUCTIONTheEastChinaSea,withanaveraged5oOkmcontinentalshe1f,containslargeamountofnaturalresourcesandfishinggrounds.ThewarmandsalineKuroshiowhichoriginatesfromtheNorthEquatorialCurrentintrudesintothisarea.ManylargeriverssuchastheChangjiangRiverandtheQiantangRiverprovidea1otoffreshwatertotheEastChinaSea.Somanywatersource%thecomplicatedoceantoPOgraphyasw…     

Reflection Coefficient Calculation from Marine High Resolution Seismic Reflection (Chirp) Data and Application to an Archaeological Case Study

Chirp sub-bottom profilers produce high-resolution images of the near-surface. An attribute of the sea-bed reflection in chirp data are fluctuations in polarity between adjacent traces. Two models are proposed and presented to explain this: the first incorporates changes in an acoustic impedance gradient at the sea bed; the second uses changes in the thickness of the uppermost sediment layer. Mixing of adjacent traces produces a consistent polarity for the sea-bed reflector. Reflection coefficients are calculated, using amplitude information derived from single-traces, and polarity information from trace mixing, with application to a marine archaeological case study. The reflection coefficient calculated for the top of a buried 18th century wooden wreck is -0.26.     

多光谱遥感影像的光谱规则分类算法修正及海岛、海岸带应用

在光谱规则分类算法(Spectral Rule-based Classifier, SRC)基础上考虑大气校正对遥感影像光谱反射率的影响,提出了一种改进光谱规则的分类算法(Modified Spectral Rule-based Classifier, MSRC),从地物光谱响应曲线和光谱指数两个方面来修正光谱规则集,通过规则细化和补充、阈值改正优化光谱类别。以珠江三角洲海岛(佳蓬、淇澳)和海岸带(荃湾、惠东)的Landsat 8影像作为实验数据,对比了大气校正前后波段反射率和地物光谱响应曲线,分析了改进后MSRC算法的地物分类结果和精度,并与原SRC算法、最小距离分类(MDC)算法、最大似然分类(MLC)算法、支持向量机分类(SVM)算法、神经网络分类(NNC)算法以及基于光谱指数的算法等多种地物分类算法进行比较。结果表明,4组实验数据的MSRC算法分类结果总体精度分别为87.66%、82.38%、77.67%和80.05%,高于SRC、MDC、MLC和基于光谱指数的分类算法,在无需人工标注训练数据集的前提下接近SVM和NNC算法的分类精度。MSRC算法适用于海岛和海岸带的Lands...     

近三十年来太湖流域主要湖泊的水域变化研究

选用地形图和不同时期的遥感影像数据,利用GIS技术进行处理,获取不同时期的太湖流域主要湖泊的水域面积,并结合多种文献资料,对太湖流域主要湖泊的水域面积变化进行了研究。结果表明,太湖流域主要湖泊的水域面积,在1971~1988年间减少了159.96km2;1988~2002年间减少了28.91km2;湖泊水域面积的减少是自然因素和人类活动综合作用的结果,围湖利用是湖泊水域面积减少的主要原因。针对湖泊水域日益减少的现状,应加强对湖泊资源的保护与合理利用。     

图像融合在遥感中的应用

介绍了关于低分辨率的多光谱图像与高分辨率的全色图像相融合的一些方法。图像融合的目的是为了获取高分辨率的多光谱图像,它既包含了多光谱信息又具有全色图像的高空间分辨率特点。图像融合在遥感中的主要目的在于尽量保持图像的光谱信息．以便用于土地覆盖分类等领域,这一点与其在军事应用和计算机辅助设计领域有所不同。阐述了如何在不使用高分辨率的全色图像情况下进行融合的方法,由于同时获取的多光谱图像之间存在亚像元级的偏移现象,将位移量作为附加信息来有效提高采样频率,以此获取高空间分辨率信息。最后选取了SPOT卫星的多光谱图像作为例子．对文中所阐述的算法进行了试验,并对试验结果作了比较分析。     

考虑自由面反射作用的圆柱流噪声计算

对于现代舰船而言噪声是其关键性能之一,目前水下航行体的流激噪声预测方法已经较为成熟,但是水面舰船的水动力噪声研究起步较晚,还没有形成系统的预报方法和控制手段。使用开源CFD工具包OpenFOAM求解器,流场通过大涡模拟方法求解,自由液面则依靠VOF方法捕捉,通过Curle方程预测远场噪声,基于镜像法考虑自由面的反射作用,数值模拟近自由面圆柱周围的声场分布。开展了Re=3 900下距离自由液面不同高度的圆柱辐射噪声求解,主要结合流场分析自由面对声场的扰动作用和不同深度对水下几何体流噪声的影响。初步考虑了自由液面波形对辐射噪声的反射作用,为后续预测水面舰船的水动力噪声特性提供依据,自由面对辐射噪声的阻抗等作用还需进一步研究。     

THE RELATIONSHIP BETWEEN ACTUAL AND COGNITIVE STATE SIZES*

Relative size is a spatial concept that can increase our understanding of environmental cognition. Data from questionnaires tested several hypotheses about size distortion of states. Subjects distorted sizes logarithmically except in a zone of indiscrimination that included eight states. Male subjects were more accurate than female subjects in the estimation of actual state sizes; however, a sex-linked territoriality was not identified.     

Image Filtering by Factorial Kriging—Sensitivity analysis and application to Gloria side-scan sonar images

Factorial Kriging (FK) is a data- dependent spatial filtering method that can be used to remove both independent and correlated noise on geological images as well as to enhance lineaments for subsequent geological interpretation. The spatial variability of signal, noise, and lineaments, characterized by a variogram model, have been used explicitly in calculating FK filter coefficients that are equivalent to the kriging weighting coefficients. This is in contrast to the conventional spatial filtering method by predefined, data-independent filters, such as Gaussian and Sobel filters. The geostatistically optimal FK filter coefficients, however, do not guarantee an optimal filtering effect, if filter geometry (size and shape) are not properly selected. The selection of filter geometry has been investigated by examining the sensitivity of the FK filter coefficients to changes in filter size as well as variogram characteristics, such as nugget effect, type, range of influence, and anisotropy. The efficiency of data-dependent FK filtering relative to data-independent spatial filters has been evaluated through simulated stochastic images by two examples. In the first example, both FK and data-independent filters are used to remove white noise in simulated images. FK filtering results in a less blurring effect than the data-independent fillers, even for a filter size as large as 9 × 9. In the second example, FK and data-independent filters are compared relative to the extraction of lineaments and components showing anisotropic variability. It was determined that square windows of the filter mask are effective only for removing Isotropie components or white noise. A nonsquare windows must be used if anisotropic components are to be filtered out. FK filtering for lineament enhancement is shown to be resistant to image noise, whereas data-independent filters are sensitive to the presence of noise. We also have applied the FK filtering to the GLORIA side-scan sonar image from the Gulf of Mexico, illustrating that FK is superior to the data-independent filters in removing noise and enhancing lineaments. The case study also demonstrate that variogram analysis and FK filtering can be used for large images if a spectral analysis and optimal filter design in the frequency domain is prohibitive because of a large memory requirement.     

地图扫描数字化的点位精度分析

地图扫描数字化为建立ＧＩＳ提供了一种较好的原始地图数据获取方法，本文讨论了影响地图扫描数字化精度的诸种因素，分析了定向点和采样点误差对地图数字化结果的影响，发展了定向点和采样点的自动对中算法，从而保证地图扫描数字化的精度能满足建立ＧＩＳ的要求。