基于Manhattan距离的相干体技术的应用     

刘海燕  刘财  刘洋  张营  高凤霞 《世界地质》2013,32(1):144-152

地震相干体技术可以有效地压制连续性,突出不连续性,比地震切片的地质解释更直观,能更细致地进行断层解释。基于Manhattan 距离的相干体技术,与传统的C1 相干算法进行比较,该技术不仅在断层识别能力方面要强于C1 相干算法,而且当利用两种算法获取断层信息的效果相当时,该技术的相关时窗长度要比C1 相干算法所用的相关时窗长度小,这恰能提高程序的运行速度,提高了地震相干体技术的运行效率。此外,该相干体技术也能近似计算出每道在纵横测线方向上的视时间倾角。  相似文献   

遗传门限自回归模型在气象时间序列预测中的应用   总被引：5，自引：2，他引：5  

金菊良  杨晓华  金保明  丁晶 《热带气象学报》2001,17(4):415-422

提出了建立门限自回归模型（TAR）的一套简便通用的方法。用基于实码的改进遗传算法，可同时优化门限值和自回归系数，解决了TAR建模过程所涉及的大量复杂寻优工作这一难题，为TAR模型在气象预测中的广泛应用提供了有力工具。实例计算的结果说明：通过门限值的控制作用，TAR模型可有效地利用气象时序资料所隐含的时序分段相依性这一重要信息，限制了模型误差，保证了TAR模型预测性能的稳健性，提高了预测精度。该方法具有通用性，在各种气象非线性时序预测中具有广泛的实用价值。  相似文献   

遗传算法及其在速度结构与震源联合反演中的应用   总被引：2，自引：0，他引：2  

黄河  任韶萱 《东北地震研究》1998,14(4):1-14

遗传算法是近年来发展较快的一种求解多参数非线性优化问题的有效方法。本文通过对遗传传算法的介绍。对该方法的发展现状及特点进行了分析,在此基础上,对遗传算法进行了改进：通过引入放大系统Ｋ。对目标函数进行压缩及扩展来提高遗传算法的搜索机制;  相似文献   

Objective regionalization of Rayleigh wave dispersion data by clustering algorithms: an application to the Mediterranean basin     

M. D. Martí  nez  J. A. Canas  X. Lana  J. Badal 《Tectonophysics》2001,330(3-4):245-266

The main target of the present study is an objective and automated regionalization of Rayleigh wave dispersion data for the Mediterranean basin, without a priori seismotectonic constraints, and to determine the corresponding regional shear-velocity structures. The database used is formed by almost 200 Rayleigh wavetrains corresponding to 42 regional events, with surface-wave magnitude greater than 4.5, recorded at the MedNet very-broad-band stations in the Mediterranean area. Path-averaged group velocities for the Rayleigh wave fundamental mode are derived for each available epicentre-station trajectory crossing the Mediterranean basin. After this, a principal component analysis and a clustering process are applied to local group velocities, obtained for 13 different periods from 10 to 70 s, in order to classify the Mediterranean basin into several homogeneous regions. The stochastic inversion of the averaged group velocity dispersion curve obtained for each region provides the respective shear-velocity structures, down to a depth of 150–160 km. The characteristics of these areas and their possible correlation with the main seismotectonic features of the Mediterranean region are discussed. The regional models reveal significant lateral changes in the elastic structure, with the main differences concerning particularly the upper 35–40 km. Within this depth range, low shear velocities, varying from 2.8 to 3.9 km s⁻¹, characterize the Eastern Mediterranean, whereas higher velocities, ranging from 3.0 to 4.2 km s⁻¹, are deduced for the Western Mediterranean. These results suggest a thicker crust in the eastern part, but with a greater thickness of sedimentary layers. However, for depths of between 80 and 110 km, lower shear velocities are obtained in the Western part, while higher shear velocities are derived for the Eastern Mediterranean Sea, in the Aegean Sea, Greece, the south of Italy, Sicily and Tunisia. This velocity pattern suggests an averaged thicker lithosphere under the latter areas, as the top of the asthenosphere is detected at a mean depth of 75 km for the remaining regions. This thicker lithosphere can be related to processes associated with the convergence of the Eurasian and African plates and subduction under the Calabrian and Hellenic Arcs.  相似文献   

Retrieval of leaf area index in alpine wetlands using a two-layer canopy reflectance model     

《International Journal of Applied Earth Observation and Geoinformation》2013

In this paper, we focused on the retrieval of the LAI in an alpine wetland located in western part of China in late August and early July 2011. A two-layer canopy reflectance model (ACRM) was used to establish the relationships between the LAI and the reflectance of near-infrared (NIR) and red (RED) wavebands. The reflectance data were derived from Landsat TM L1T product and the Terra and Aqua MODIS 16-day and 8-day composite reflectance products (MOD/MYD09) at 250 m resolution. Due to the lack of the information about some major input parameters for ACRM, which are sensitive to model outputs in the reflectance of NIR and RED wavebands, the inverse problem was ill-posed. To overcome this problem, a method of increasing the sensitivity of the LAI while reducing the influence of other model free parameters based on the study of free parameters’ sensitivity to the ACRM outputs and the region’s features was studied. The area of interest was divided into two parts using the approximately statistic normalized difference vegetation index (NDVI) value around 0.5. One part was sparse vegetation (0.1 < NDVI < 0.5), which is more sensitive to soil background effects and less sensitive to the canopy biophysical and biochemical variables. The other part was dense vegetation (0.5 ≤ NDVI < 1.0), which is less sensitive to soil background effects and more sensitive to plant canopies and leaf parameters. Then, the relationships of ρ_nir–LAI and ρ_red–LAI were established using a look-up table algorithm for the two parts. Furthermore, a regularization technique for fast pixel-wise retrieval was introduced to reduce the elements of LUT sets while maintaining a relatively high accuracy. The results were very promising compared to the field measured LAI values that the correlation (R²) of the measured LAI values and retrieved LAI values reached 0.95, and the root-mean-square deviation (RMSD) was 0.33 for late August, 2011, while the R² reached 0.82 and RMSD was 0.25 for early July 2011.  相似文献   

Topologically Safe Curved Schematisation     

《The Cartographic journal》2013,50(3):276-285

Abstract

Traditionally schematised maps make extensive use of curves. However, automated methods for schematisation are mostly restricted to straight lines. We present a generic framework for topology-preserving curved schematisation that allows a choice of quality measures and curve types. The framework fits a curve to every part of the input. It uses Voronoi diagrams to ensure that curves fitted to disjoint parts do not intersect. The framework then employs a dynamic program to find an optimal schematisation using the fitted curves. Our fully-automated approach does not need critical points or salient features. We illustrate our framework with Bézier curves and circular arcs.  相似文献   

基于GPS和MODIS数据的大气可降水量反演算法研究     

张俊东;陈秀万;李颖;罗鹏;万玮;曹艳丰 《东北测绘》2013,(2):59-62,66

基于高精度的PWVGPS与MODIS近红外三通道比值透射率间的关系建立MODIS大气可降水量新反演算法以提高反演精度。利用美国Kansas州和Oklahoma州2009年4月～9月间17期的MODIS数据和对应的SuomiNet网PWVGPS数据进行研究,发现Kaufman和Gao Bo-Cai算法反演的PWVMODIS系统性地偏低于PWVGPS,存在较大的反演误差。以高精度的PWVGPS为标准水汽值,研究PWVGPS与MODIS近红外第19波段的三通道比值透射率间的关系,建立了MODIS大气可降水量新反演算法,并利用研究区数据进行试验验证,结果表明新算法可大幅提高PWVMODIS的反演精度。  相似文献   

顾及不确定因素的GA-BP神经网络在路基沉降预测中的应用     

杨发群  邱卫宁  魏成  李成贤 《测绘工程》2013,(6):51-54

BP神经网络初始权值和阈值输入不同,将导致BP神经网络预测不稳定,精度也不是很高.通过遗传算法（GA）对BP神经网络的初始权值和阈值进行优化,能很大程度上提高预测的精度,但是,由于输入层不可能将影响输出的所有因素都包含在内,而这些没有考虑到的因素势必影响预测结果.文中将这些无法得知的不确定因素当做一个综合影响因素,定义为X因素,在建立模型时加以考虑.实验结果表明,这种顾及不确定因素的GA-BP神经网络模型能进一步提高预测精度.  相似文献   

极区海冰密集度AMSR-E数据反演算法的试验与验证   总被引：4，自引：2，他引：2  

苏洁  郝光华  叶鑫欣  王维波 《遥感学报》2013,17(3):495-513

海冰密集度是极区海冰监测的重要参数,目前分辨率最高的微波海冰密集度产品为德国Bremen大学发布的针对AMSR-E 89 GHz频段数据利用ASI算法反演的网格数据。为实现中国极区遥感产品从无到有的战略步骤,本文针对AMSR-E 89GHz频段微波数据的ASI算法,进行了插值算法、系点值和天气滤波器一系列试验。针对北极海区,着重对影响反演结果的主要参数——纯冰和纯水的亮温极化差异阈值,即系点值(P₁和P₀)进行了2009年全年的统计分析。研究表明,2009年北极纯冰和纯水的代表区域P₁和P₀年平均值分别为10.0 K和46.67 K;2 K以上的系点值差异引起的海冰密集度差别较为显著;同样的系点值差异在不同极化差异P取值范围对海冰密集度的影响也不同。通过统计确定的系点值推算并修正了海冰密集度反演公式,对2009年全年北极海冰密集度进行了反演,并与Bremen大学产品进行了比较。继而对白令海和楚科奇海12个晴空下MODIS可见光样本数据进行反演,以验证AMSR-E冰密集度反演结果,并对误差原因进行了分析。本研究反演结果与MODIS样本比对的误差略小于Bremen大学的反演产品,空间平均误差为3.84%,空间平均绝对误差10.83%。  相似文献   

基于3S技术的收获期农机调度     

任建顺  齐清文  周芳  刘雪  龚泽仪 《测绘科学》2013,38(2):44-46

农作物系统本身具有显著的时空变异性,忽略作物成熟日期的差异采取相同的收获日期可能会造成实际收获产量、质量的损失,使用3S技术进行科学合理的农机调度是减少这一损失的重要前提。本文使用获取的遥感数据反演了作物的成熟日期,并在分析了农机时空调度的依据和限制条件的基础上,提出了农机时空调度问题,使用改进的遗传算法构建了农机时空调度模型和算法并使用MATLAB进行了程序实现,最后构建了基于3S技术的农机调度技术框架。  相似文献