Seismic site effects by an optimized 2D BE/FE method II. Quantification of site effects in two-dimensional sedimentary valleys

This paper deals with the evaluation of seismic site effects due to the local topographical and geotechnical characteristics. The amplification of surface motions is calculated by a numerical method combining finite elements in the near field and boundary elements in the far field (FEM/BEM). The numerical technique is improved by time truncation. In the first part of this article, the accuracy and the relevance of this optimized method are presented. Moreover, parametric studies are done on slopes, ridges and canyons to characterize topographical site effects. The second part deals with sedimentary valleys. The complexity of the combination of geometrical and sedimentary effects is underlined. Extensive parametrical studies are done to discriminate the topographical and geotechnical effects on seismic ground movement amplifications in two-dimensional irregular configurations. Characteristic coefficients are defined to predict the amplifications of horizontal displacements. The accuracy of this quantitative evaluation technique is tested and discussed.     

平面四孔六边形格网系统复进制数建模及编码运算

格网系统是一种多分辨率栅格数据结构,在多尺度地理空间数据组织、处理和分析中应用广泛.六边形格网系统具有重要几何特性,相关研究已引起学术界广泛关注,格网层次关系描述及计算是研究难点之一.本文引入复进制数理论,通过间隔层次格网单元隶属关系,建立平面四孔六边形格网系统数学模型,据此提出等效编码方案,定义编码运算并归纳运算规则,设计编码索引、编码与笛卡儿坐标互换算法.对比试验结果表明,本文提出的编码方案与同类成果相比具有结构对称性,可显著提高编码操作效率,具有实际应用潜力.     

线性四叉树快速动态编码及其实现

对常规线性四叉树编码方法存在的不足进行了分析 ,提出了一种在遍历栅格数据过程中直接生成四叉树的快速动态编码方法。该方法用栈代替线性表或数组 ,在提取格网单元后 ,直接检测其属性值 ,生成十进制Morton码。将这些数据压入栈 ,在栈中同步地对已检测过的格网单元或结点向上层结点进行合并。当对整个栅格数据遍历完后 ,栈中剩下的记录就是所需要的线性四叉树编码结果。最后根据测试结果比较了动态编码与常规编码方法的运行效率和内存占用量。结果表明 ,快速动态编码明显优于其他编码方法     

气象装备全寿命自动跟踪编码设计

介绍了气象装备需要编码的背景,编码设计原则。阐述了气象装备的分类规则和编码设计,并通过一个例子说明了编码的使用方式。设计的编码在实现唯一性标识的同时体现了气象业务特性的特点。编码设计中采用了含义编码、并置码、层次码顺序递增码等编码方法,区分了固定码和动态码,固定码规范了气象装备编码规则,动态码实现了气象装备的信息化动态管理。该设计方案可以对全国气象装备进行规范化和标准化管理,具有广泛的适用性和通用性。     

一种岩性提取新方法--光谱排序编码法

光谱排序编码法(SSE:Spectra Sort Encoding Algorithm)是在对目标光谱与地物光谱按光谱强度大小进行排序的基础上,计算两条光谱曲线的相似度,然后,根据相似度与识别误差进行编码,从而达到识别目标的目的.文章详细介绍了算法提出的背景、原理,并对算法在岩性提取中的精度进行对比验证,结果表明在识别误差从0到0.3变化的过程中,算法最高精度的平均值为1,平均精度的平均值为0.825.高精度是其进行岩性提取的基础,岩性端元提取对比试验的结果也证明它是一种有效的岩性提取算法.     

主动源勘探中震源编码与解码方法

依据人工主动震源的可控性,引入通讯中的编码原理,采用震源编码技术能够有效提高小当量人工震源的探测深度和信号接收距离。笔者分析研究了主动源勘探中的震源编码与解码方法,主要做了以下工作:①分析研究了震源信号自相关函数的基本性质,探讨了利用自相关函数峰值间的零值区进行信号检测的可能性,研究表明编码方法能够通过相关增加有效信息的检测范围,提高监测能力;②研究了震源编码的三种基本方式,分析了它们的旁瓣压制效果,通过不同激发能量的源在不同时刻重复激发建立编码震源,信号能够在相关峰值和相关旁瓣间有效检测出;③探讨了迭代相关法解码的基本原理,编码方法能够大幅度提高地震探测能力,利用小能量震源获得大的探测距离和高分辨率,具有很强的抗干扰能力。     

月球地质图空间数据库设计

我国即将完成1: 2 500 000全月球数字地质图编制,为便于成果数据存储管理和集成共享,需要建立完备合理的空间数据库。本文基于本次编图工作实践,对月球地质图空间数据库要素内容进行了全面整理和归类。月球地质图空间数据库要素包括物质要素、构造要素、其他特殊符号、注记共4个大类,在大类基础上细分为13个中类及40个小类,并据此设计了具有可扩展性的要素分类代码。空间要素采用分层的方式进行组织管理,图层名前4位为所属图幅号,第5位为比例尺代码,其后为图层英文名称的缩写。每个要素图层与一张属性表关联,对属性表所有字段的字段名称、别名、类型、能否为空、长度、小数位及单位进行了定义和规范。本文选取月表撞击坑坑物质、月海岩石、撞击断裂及高程点要素详细阐述了其属性表结构。属性表主键为“要素标识号”,用于唯一标识某一个图元,其由图幅号、比例尺代码、要素分类代码、图元顺序码四层14位层次码构成。数据库设计遵循可扩展原则,特定区域或其他比例尺的月球地质图空间数据库建设也可参照执行,本文以月球冯·卡门撞击坑及邻区地质图为例进行了空间数据库设计。科学合理的数据库设计是数据库建设的前提,将为编图成果存储管理、集成共享与国际合作提供重要支撑。     

Remote-sensing data-based Archaeological Predictive Model (APM) for archaeological site mapping in desert area,South Morocco

Morocco hosts numerous archaeological sites, some of which are part of the UNESCO world heritage. Many of these sites, especially funerary mounds also called tumuli, or rock engravings and ceramics, are located in remote areas with limited access, particularly in the Saharan Morocco desert. We developed a remote sensing and GIS model to identify areas with high potential for hosting archaeological sites in the Awserd region of southern Morocco. A field campaign in a “reference site” zone of 21 km² has revealed 233 archaeological sites. Here we use satellite images and Digital Elevation Models to examine with various techniques (spatial analysis, statistical techniques, and fuzzy logic functions) the relations between the distribution of the archaeological sites and geo-environmental variables such as ground geology, topographic elevation and slope, orientation (aspect), and distance to water sources. We derive empirical relations that reveal that the distribution of archaeological sites depends on the above geo-environmental variables. We then use the empirical relations to anticipate the potential locations of archaeological sites in a region of 980 km² enclosing the reference site area. The model proves capable of predicting 582 sites in the larger region. Subsequent field observations there confirmed that about 80% of the model anticipations were correct. Our Archaeological Predictive Model (APM) can be scaled to larger areas and varied geographic settings, and hence can be a useful guide for archeological studies in desert regions.     

Comparative analysis of different retrieval methods for mapping grassland leaf area index using airborne imaging spectroscopy

Fine scale maps of vegetation biophysical variables are useful status indicators for monitoring and managing national parks and endangered habitats. Here, we assess in a comparative way four different retrieval methods for estimating leaf area index (LAI) in grassland: two radiative transfer model (RTM) inversion methods (one based on look-up-tables (LUT) and one based on predictive equations) and two statistical modelling methods (one partly, the other entirely based on in situ data). For prediction, spectral data were used that had been acquired over Majella National Park in Italy by the airborne hyperspectral HyMap instrument. To assess the performance of the four investigated models, the normalized root mean squared error (nRMSE) and coefficient of determination (R²) between estimates and in situ LAI measurements are reported (n = 41). Using a jackknife approach, we also quantified the accuracy and robustness of empirical models as a function of the size of the available calibration data set. The results of the study demonstrate that the LUT-based RTM inversion yields higher accuracies for LAI estimation (R² = 0.91, nRMSE = 0.18) as compared to RTM inversions based on predictive equations (R² = 0.79, nRMSE = 0.38). The two statistical methods yield accuracies similar to the LUT method. However, as expected, the accuracy and robustness of the statistical models decrease when the size of the calibration database is reduced to fewer samples. The results of this study are of interest for the remote sensing community developing improved inversion schemes for spaceborne hyperspectral sensors applicable to different vegetation types. The examples provided in this paper may also serve as illustrations for the drawbacks and advantages of physical and empirical models.