基于栅格数据提取主骨架线的新算法     

杜世宏  杜道生  樊红  万幼川 《武汉大学学报(信息科学版)》2000,25(5):432-436

详细介绍了基于栅格数据的面状地物主骨架线的提取算法。该算法具有较快的处理速度和较强的适应性及内存需求少的优点 ,同时用该算法所提取的主骨架线为最优 (最长 )骨架线 ,可用于面状地物注记的自动配置。  相似文献   

数字制图中生僻汉字信息处理     

刘新贵  阚映红 《测绘与空间地理信息》2000,23(3):6-7,10

在 1:2 50 0 0 0地图数据库生僻汉字统计的基础上 ,通过生僻汉字的编码、字模的制作、代码的编制、输入法的生成以及矢量汉字的使用等 ,提出了在GBK的基础上进行再扩展的技术和方法 ,从而解决了数字制图中生僻汉字处理的问题。  相似文献   

GIS中数字化数据误差的分布检验与处理     

童小华  史文中  刘大杰 《武汉大学学报(信息科学版)》2000,25(1)

对ＧＩＳ中手工地图数字化中的数据误差进行了系统分析和各种分布检验,认为数字化数据误差可能服从ｐ≈１．６的ｐ－范分布。在此基础上,探讨了数字化数据误差处理的ｐ－范平差,并与最小二乘平差进行了比较。  相似文献   

The effect of clouds on aerosol growth in the rural atmosphere   总被引：1，自引：0，他引：1  

Colin D. O'Dowd  Jason A. Lowe  Michael H. Smith 《Atmospheric Research》2000,54(4):1331

Measurements of accumulation mode aerosol in the atmospheric boundary layer under cloudy and cloud-free conditions, and in the lower free troposphere under cloud-free conditions, were conducted over the rural northwest of England. Normalised size distributions in the cloud-free boundary layer (CFBL) and the cloud-free free troposphere (CFFT) exhibited almost identical spectral similarities with both size distributions possessing a concentration peak mode-radius of ≈0.05 μm or less. By comparison, aerosol distributions observed in cloudy air exhibited a distinctive log-normal distribution with mode-radii occurring at ≈0.1 μm concomitant with a local minimum at ≈0.05 μm. The consistent and noticeable difference in spectral features observed between cloudy and cloud-free conditions suggest that a greater amount of gas-to-particle conversion occurs on cloudy days, presumably through in-cloud aqueous phase oxidation processes, leading to larger sized accumulation mode particles. Apart from the distinct difference between cloudy and cloud-free aerosol spectra on cloudy days, aerosol concentration and mass were observed to be significantly enhanced above that of the ambient background in the vicinity of clouds. Volatility analysis during one case of cloud processing indicated an increase in the relative contribution of aerosol mass volatile at temperatures characteristic of sulphuric acid, along with a smaller fraction of more volatile material (possibly nitric acid and/or organic aerosol). Growth-law analysis of possible growth mechanisms point to aqueous phase oxidation of aerosol precursors in cloud droplets as being the only feasible mechanism capable of producing the observed growth. The effect of cloud processing is to alter the cloud condensation nuclei (CCN) supersaturation spectrum in a manner which increases the availability of CCN at lower cloud supersaturations.  相似文献   

探空资料质量控制及可视化处理系统(HBTK)的研究与应用   总被引：1，自引：0，他引：1  

张峻 《气象》2000,26(3):33-36

介绍了“探空资料质量控制及可视化处理系统 ( HBTK)”的基本功能、设计技术和应用效果 ,实践证明该系统不受测站个体差异的影响 ,具有很好的实用性。  相似文献   

地震资料处理中的聚束滤波方法   总被引：33，自引：11，他引：22       下载免费PDF全文

胡天跃  王润秋  R.E. WHITE 《地球物理学报》2000,43(1):105-115

聚束滤波方法的基本原理,包括信号与噪音模型、设计准则和所获得的聚束滤波器．本文所用的自适应聚束滤波器是根据具有参数化的动校正量、振幅及相位随偏移距变化（ＭＶＯ、ＡＶＯ及ＰＶＯ）的一次反射和多次反射信号模型而设计的．但在实际应用中ＰＶＯ通常不能得到证实．结果分析能为进一步的从ＡＶＯ及ＰＶＯ获取岩石类型信息的专题研究提供资料．人工合成资料的例子给出了参数化的自适应聚束滤波的实施细节和所设计滤波器的响应特性．实际资料的例子表明数据自适应聚束滤波在叠前共中点道集地震多次波消除上比Ｒａｄｏｎ变换方法更灵活、有效．类似于其它叠前处理过程,自适应聚束滤波的优越性在信噪比较高的资料上体现得最为明显．  相似文献   

A global river routing network for use in hydrological modeling   总被引：2，自引：0，他引：2  

H. Renssen  J. M. Knoop   《Journal of Hydrology》2000,230(3-4):230-243

In this paper a relatively simple procedure is presented to construct a global river routing network on a 0.5° latitude–longitude grid. In this network all grid cells in a catchment are coupled and have a flow direction, making it a useful tool in the modeling of river flow on a global scale. The flow directions are based on a digital elevation model and on information on the locations of major rivers (‘stream burning’). The presented river routing network is specifically designed for the assessment of fresh water shortages. We tested the validity of the river routing network by comparing the computed drainage areas with published estimates. This comparison revealed a good similarity and it is concluded that the presented river routing network has sufficient quality to be implemented in global climate models. This could mean a considerable improvement of the surface parameterization in these models.  相似文献   

Ground clutter cancellation in incoherent radars: solutions for EISCAT Svalbard radar     

T. Turunen  J. Markkanen  A. P. van Eyken 《Annales Geophysicae》2000,18(9):1242-1247

Incoherent scatter radars measure ionosphere parameters using modified Thomson scatter from free electrons in the target (see e.g. Hagfors, 1997). The integrated cross section of the ionospheric scatterers is extremely small and the measurements can easily be disturbed by signals returned by unwanted targets. Ground clutter signals, entering via the antenna side lobes, can render measurements at the nearest target ranges totally impossible. The EISCAT Svalbard Radar (ESR), which started measurements in 1996, suffers from severe ground clutter and the ionosphere cannot be measured in any simple manner at ranges less than about 120–150 km, depending on the modulation employed. If the target and clutter signals have different, and clearly identifiable, properties then, in principle, there are always ways to eliminate the clutter. In incoherent scatter measurements, differences in the coherence times of the wanted and unwanted signals can be used for clutter cancellation. The clutter cancellation must be applied to all modulations, usually alternating codes in modern experiments, used for shorter ranges. Excellent results have been obtained at the ESR using a simple pulse-to-pulse clutter subtraction method, but there are also other possibilities.  相似文献   

努和廷地区古河道砂岩型铀矿遥感信息提取   总被引：1，自引：0，他引：1  

刘建军 《铀矿地质》2000,16(1):52-57

本文概述了努和廷古河道砂岩型铀矿的成因及形成机理、介绍了采用遥感数字图像信息增强技术、钻孔资料的三维量化分析等技术,对该地区古河道砂岩型铀矿的成矿环境信息及威古河道信息的提取进行的方法研究与试验。  相似文献   

新型地震信息反馈系统接收单元的研制     

叶春明  何寿清  王国望  张彪 《华南地震》2000,20(4):32-35

地震信息反馈系统接收单元由机芯、单片机及其附属电路组成,可完成地震信息的接收、解码及信号传送等。介绍了它的原理和功能,并对主要电路进行了详细分析。  相似文献