利用R语言半自动化提取河流阶地——以米家山黄河阶地为例

构造活跃地区阶地的发育对于分析不同时间域下的构造变形或气候作用具有重要意义。因此,如何利用有效的定量方法提取和精细刻画这类地貌特征显得极为重要。R语言是一种集统计分析和图形显示于一体的优秀编程语言,目前已被广泛应用于医学、生物学等领域,但尚未应用于地质与地貌学领域。文中以海原断裂带景泰—哈思山段的米家山东侧保存较好的多级黄河河流阶地为研究目标,初步尝试基于R语言对Sf M技术获取的高精度地形数据进行分析和可视化,完成了对米家山黄河阶地的半自动提取,共划分出20级河流阶地,同时揭示出较年轻的阶地具有较好的连续性和延伸性,而较老阶地的连续性和延伸性则相对较差,且老阶地变形逐渐趋于明显,阶地年龄越老,其似半抛物线形态的翘曲越明显,反映了米家山东侧多级阶地形成后的不同演化历史。此次试验结果表明R语言有望成为高精度地形数据分析和可视化的有效工具。     

Use of multitemporal remote sensing data for mapping the Alfios River network changes from 1977 to 2000

Alfios is the biggest river of the Peloponnese and the ninth longest river in Greece. It drains an area of almost 2575 km² in Western Peloponnese and discharges at Kiparissiakos Gulf. Due to its extent, the Alfios basin presents complex physiography and geomorphology.

During the last 50 years, major direct human activities have had an important impact on the river network shape and on the valley floor morphology. The most important human activities were the channel straightening caused by meander cut-offs in 1950, the construction of two dams: the Ladonas dam in 1955 and the Flokas dam in 1968 and the illegal in-stream gravel extraction that started in the 1960s and continues until today. As a result, the Alfios riverbed has presented very rapid vertical and horizontal (lateral) erosion and significant changes to its network shape. The drainage network follows a straighter course, the number of meanders has been reduced and the seventh order branch is deeply incised. Besides the morphological impacts to the river network shape there are also serious economic damages caused by human activity. During the winter of 1999, the Flokas dam bridge was closed for a long period due to damages at its foundation caused by the heavy rain and illegal gravel extraction. Transportation between the villages in the area became extremely difficult and time consuming and the cost of the repairs was estimated at 500 000 euros. In this study, there is an effort to map the network shape transformation for the period 1977–2000 using multitemporal and multisensor satellite images. One Landsat MSS image, three Landsat TM images, two Landsat ETM images, and one Terra ASTER image have been orthorectified and processed in order to cover the specific period. Principal Component Analysis (PCA) method and Geographical Information System (GIS) techniques have been applied to map the changes in the Alfios River channel. The drainage network straightening and the cut-off of five big meanders were detected and mapped. These changes occurred between 1986 and 2000.     

城市基础地理信息管理系统的设计与实现

简述利用GIS进行数据管理和分析的优势,采用SuperMap Objects控件和VB6.0设计与开发基于压缩影像的城市基础地理信息管理系统,使基础地理数据更有效地服务于城市规划与管理工作。     

PolarGlobe: A web-wide virtual globe system for visualizing multidimensional,time-varying,big climate data

The increasing research interest in global climate change and the rise of the public awareness have generated a significant demand for new tools to support effective visualization of big climate data in a cyber environment such that anyone from any location with an Internet connection and a web browser can easily view and comprehend the data. In response to the demand, this paper introduces a new web-based platform for visualizing multidimensional, time-varying climate data on a virtual globe. The web-based platform is built upon a virtual globe system Cesium, which is open-source, highly extendable and capable of being easily integrated into a web environment. The emerging WebGL technique is adapted to support interactive rendering of 3D graphics with hardware graphics acceleration. To address the challenges of transmitting and visualizing voluminous, complex climate data over the Internet to support real-time visualization, we develop a stream encoding and transmission strategy based on video-compression techniques. This strategy allows dynamic provision of scientific data in different precisions to balance the needs for scientific analysis and visualization cost. Approaches to represent, encode and decode processed data are also introduced in detail to show the operational workflow. Finally, we conduct several experiments to demonstrate the performance of the proposed strategy under different network conditions. A prototype, PolarGlobe, has been developed to visualize climate data in the Arctic regions from multiple angles.     

高原地区雷暴过程地面电场变化特征分析

高原地区是我国雷暴天气多发区之一。通过对大气电场仪所测得雷电过程地面电场变化特征的分析有助于了解这一地区的雷暴特征,对认识该地区雷暴过程特征有一定的参考价值。对雷暴过程初期的地面电场波形变化的曲线拟合,总结出了共同的特征,为地面电场资料在雷电预警预报中的应用提供了参考价值。对雷暴过程地面电场资料的特征分析以及预报方面的研究都是很有现实意义的。     

The Sloan Digital Sky Survey monitor telescope pipeline

The photometric calibration of the Sloan Digital Sky Survey (SDSS) is a multi‐step process which involves data from three different telescopes: the 1.0‐m telescope at the US Naval Observatory (USNO), Flagstaff Station, Arizona (which was used to establish the SDSS standard star network); the SDSS 0.5‐m Photometric Telescope (PT) at the Apache Point Observatory (APO), NewMexico (which calculates nightly extinctions and calibrates secondary patch transfer fields); and the SDSS 2.5‐m telescope at APO (which obtains the imaging data for the SDSS proper). In this paper, we describe the Monitor Telescope Pipeline, MTPIPE, the software pipeline used in processing the data from the single‐CCD telescopes used in the photometric calibration of the SDSS (i.e., the USNO 1.0‐m and the PT). We also describe transformation equations that convert photometry on the USNO‐1.0m u ′g ′r ′i ′z ′ system to photometry the SDSS 2.5m ugriz system and the results of various validation tests of the MTPIPE software. Further, we discuss the semi‐automated PT factory, which runs MTPIPE in the day‐to‐day standard SDSS operations at Fermilab. Finally, we discuss the use of MTPIPE in current SDSS‐related projects, including the Southern u ′g ′r ′i ′z ′ Standard Star project, the u ′g ′r ′i ′z ′ Open Star Clusters project, and the SDSS extension (SDSS‐II). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

磁偏角（D）的数据处理

磁偏角观测数据既有东西方向的区别,又有数值大小的变化,由于喀仁台所处的地理纬度,其磁偏角方向偏东,观测工作就是要搞清磁照图上Ｄ与ＤＢ相对位置及Ｄ↑及Ｄ↓的物理意义;箭头表示磁场变化的向东偏的方向。在处理Ｄ观测数据时很容易发生混乱的错误,针对存在的问题,对数据处理展示了讨论。     

Approximation of Gaussian spatial autoregressive models for massive regular square tessellation data

Most of the literature to date proposes approximations to the determinant of a positive definite n × n spatial covariance matrix (the Jacobian term) for Gaussian spatial autoregressive models that fail to support the analysis of massive georeferenced data sets. This paper briefly surveys this literature, recalls and refines much simpler Jacobian approximations, presents selected eigenvalue estimation techniques, summarizes validation results (for estimated eigenvalues, Jacobian approximations, and estimation of a spatial autocorrelation parameter), and illustrates the estimation of the spatial autocorrelation parameter in a spatial autoregressive model specification for cases as large as n = 37,214,101. The principal contribution of this paper is to the implementation of spatial autoregressive model specifications for any size of georeferenced data set. Its specific additions to the literature include (1) new, more efficient estimation algorithms; (2) an approximation of the Jacobian term for remotely sensed data forming incomplete rectangular regions; (3) issues of inference; and (4) timing results.     

强夯-降水联合加固饱和软粘土地基试验研究

针对强夯法加固饱和软粘土地基时超静孔压消散难和易出现“橡皮土”的问题,提出将强夯和井点降水技术结合起来,利用井点降水技术来加速夯后超静孔压的消散和软土固结,并结合上海市某集装箱堆场工程中土部为吹填细砂、下部为饱和软粘土的地基进行了现场试验研究,对加固过程以及加固后的土体变形、超静孔压变化、工艺参数、加固效果和加固后土体的时间效应以及强夯的加固机理等进行了分析和讨论。强夯和井点降水技术的合理结合进一步拓宽了井点降水和强夯法的应用范围,为我国沿海地区广为分布的软土地基的加固问题提供了新的途径。     

Tidal current observation in the southern Yellow Sea in the summers of 2001 and 2003

Direct current observations in the Yellow Sea interior are very scarce due to intense fishing and trawling activities. Most previous studies on tides in the area were based on coastal measurements or satellite altimeter sea levels and have not been rigorously compared with direct measurements. In this paper, tidal currents are studied with current profiles from three bottom-moored Sontek Acoustic Doppler Profilers （ADPs） deployed in the southern Yellow Sea in summer of 2001 and 2003. The measured current series were dominated by tidal currents. Maximum velocities are between 40-80 cm/s at the mooring stations. M2 current is the most dominant primary tidal constituent, while MS4 and M4 are the most significant shallow water tides with much smaller amplitudes than the primary tides.