Search for point-like sources of cosmic rays with energies above 10 eV in the HiRes-I monocular data set     

《Astroparticle Physics》2007,27(6):512-520

We report the results of a search for point-like deviations from isotropy in the arrival directions of ultra-high energy cosmic rays in the northern hemisphere. In the monocular data set collected by the High-Resolution Fly’s Eye, consisting of 1525 events with energy exceeding 10^18.5 eV, we find no evidence for point-like excesses. We place a 90% c.l. upper limit of 0.8 hadronic cosmic rays/km² yr on the flux from such sources for the northern hemisphere and place tighter limits as a function of position in the sky.  相似文献   

Limitations Of The Tangent Plane Approximation For Wide-field Imaging Using The Mauritius Radio Telescope   总被引：1，自引：0，他引：1  

N. Oozeer  N. Udaya Shankar 《Astrophysics and Space Science》2002,282(1):43-55

The Mauritius Radio Telescope (MRT) is a Fourier synthesis, non-coplanar T array. The primary objective of the telescope is to survey the southern sky at 151.5 MHz in the declination range -70^° to -10^°. Due to non-coplanarity, wide-field imaging and deconvolution of wide field images made using MRT are challenging problems in applications of radio interferometric techniques. This paper discusses the usefulness and limitations of the tangent plane approximation in transforming the measured visibilities to wide field images and in estimating the point spread function (PSF) required for the deconvolution. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

量化地图图形符号透视化的展现研究     

张军海  李仁杰赵迪 梁荣玲 《地球信息科学学报》2002,4(2):77-80,84

量化地图是传递数量信息的载体 ,是量化信息可视化的图形表达方式之一。量化符号透视化是按照透视原理来设计符号 ,在对透视符号分析的基础上 ,从数学基础的角度将透视符号分为比率符号透视化、透视坐标系量化图形与透视立体地图 3类。量化符号透视化有助于某些数量指标的表达 ,提高量化地图的展现力。  相似文献   

Mapping folds and fractures in basement and cover rocks using UAV photogrammetry,Cape Liptrap and Cape Paterson,Victoria, Australia     

《Journal of Structural Geology》2016

Brittle and ductile deformation of alternating layers of Devonian sandstone and mudstone at Cape Liptrap, Victoria, Australia, resulted in upright folds with associated fold accommodation faults and multiple fracture sets. Structures were mapped at the Fold Stack locality at Cape Liptrap using high-resolution aerial photographs acquired by a digital camera mounted on an unmanned aerial vehicle (UAV). Subsequent photogrammetric modelling resulted in georeferenced spatial datasets (point cloud, digital elevation model and orthophotograph) with sub-cm resolution and cm accuracy, which were used to extract brittle and ductile structure orientation data. An extensive dataset of bedding measurements derived from the dense point cloud was used to compute a 3D implicit structural trend model to visualise along-strike changes of Devonian (Tabberabberan) folds at the Fold Stack locality and to estimate bulk shortening strain. This model and newly collected data indicate that first generation shallowly south-southwest plunging upright folds were gently refolded about a steeply plunging/subvertical fold axis during a Devonian low-strain north–south shortening event. This also led to the local tightening of first generation folds and possibly strike-slip movement along regional scale faults. In order to distinguish fractures associated with Devonian compression from those that formed during Cretaceous extension and later inversion, we compared the five fracture sets defined at Cape Liptrap to previously mapped joints and faults within the overlying sedimentary cover rocks of the Cretaceous Strzelecki Group (Gippsland Basin), which crop out nearby. An east-southeast trending fracture set that is not evident in the Strzelecki Group can be linked to the formation of Devonian folds. Additionally, hinge line traces extracted from the Fold Stack dataset are aligned parallel to a dominant fracture set within the overlying cover sediments. This suggests that basement structures (folds and coeval parallel faults) have an important influence on fault and joint orientations within Cretaceous cover rocks.  相似文献   

Lake George revisited: new evidence for the origin and evolution of a large closed lake,Southern Tablelands,NSW, Australia. 2: earliest Pleistocene (Gelasian) environments     

M. Macphail  L. K. Fifield  B. Pillans  G. Hope 《Australian Journal of Earth Sciences》2016,63(4):453-468

The three sedimentary units infilling Lake George provide the longest quasi-continuous sedimentary record of any Australian lake basin. A combination of cosmogenic nuclide burial, magnetostratigraphy and biostratigraphic dating techniques previously has shown that the basal (fluvial) unit, the Gearys Gap Formation, began accumulating at ca 4 Ma, in the early Pliocene (Zanclean), and (ii) deposition had ceased by ca 3 Ma, in the mid-late Pliocene (Piacenzian). The same techniques confirm the middle unit, the (fluvio-lacustrine) Ondyong Point Formation began accumulating in the late Pliocene and deposition continued into the earliest Pleistocene (Gelasian) when a shallow but probably laterally extensive freshwater lake extended across the drillhole site. Our data provide a minimum Gelasian age for tectonic blockage of former spillway(s) and formation of paleo-Lake George. Whether this was the earliest lake to form within the basin is unknown, since the dated intervals are separated by a ferric hardpan, interpreted as representing a prolonged period of erosion or non-deposition. Temperate rainforest angiosperms including Nothofagus growing during the late Pliocene had been extirpated or become extinct during this interval, although a number of gymnosperms, now endemic to New Caledonia, New Guinea, New Zealand and Tasmania still survived in the otherwise sclerophyll-dominated vegetation. The succession of plant communities is considered to be due to effectively drier local conditions, which in turn reflect regional aridification during the Plio-Pleistocene transition, despite the formation of a freshwater lake across the basin. The sequence provides a reliable framework for recognising and correlating Plio-Pleistocene deposits elsewhere on the Southern Highlands.  相似文献   

三维激光扫描技术在河道测量中的应用     

于海洋  罗玲  杨强  马慧慧 《测绘学报》2015,(Z1):49-53

传统的河道测量工作量大、效率低、采样密度有限,其数据获取方式和数据处理模式已经不能满足河道信息化的需要。三维激光扫描技术为空间三维信息的获取提供了全新的技术手段。本文以焦作市新河为试验区,采用Riegl VZ-1000三维激光扫描仪获取枯水期河道数据,首先对获取的河道激光点云数据进行预处理,包括数据拼接、坐标转换、点云数据滤波分类处理等,采用反距离加权插值(IDW)算法生成DEM和基于DEM自动获取断面的方法,实现了河道断面的提取,并对断面数据进行了精度分析,建立了基于三维激光扫描技术的河道水上地形信息提取技术流程。  相似文献   

基于网络爬虫的导航深度服务信息自动采集     

陈睿嘉  康志忠  张卫涛 《测绘工程》2015,(1):17-24

根据近来对地理信息Web服务搜索引擎的研究,设计一种基于网络爬虫自动采集POI(Point Of Interest)深度服务信息的方法。使用网络爬虫与DOM(Document Object Model)技术从发布相关POI深度服务信息的网站抓取实时信息,并通过编辑距离与针对地址匹配的改进最大公共子序列分析页面内容与POI主题相关度,进而将相关度最高的深度服务信息与POI点匹配,生成深度服务信息点特征。实验证明了方法的有效性。  相似文献   

基于JSON的天地图要素符号表达与解析     

欧立业  袁武彬  廖明 《测绘与空间地理信息》2015,(12):27-29

介绍了Web2.0环境下公众对地理信息使用的需求以及天地图应用现状,分析了基于现有模式公众用户与天地图实现个性化交互的不足之处,针对不足提出了用JSON格式来表达与解析要素符号,并结合试验对相关关键技术做了测试和论证分析。  相似文献   

基于图例元的统计专题地图图例符号自动生成模型的研究   总被引：1，自引：0，他引：1  

王玉晶  江南  张亚军  王培 《测绘科学技术学报》2015,(6):635-639

通过分析统计专题地图图例符号的分类和特点,提出了图例元的概念。在对图例元分类及形式化描述的基础上,构建了基于图例元的统计专题地图图例符号自动生成模型;设计并实现了统计专题地图图例的自动生成模块,最终应用到统计专题地图的制作过程中。结果表明,该模型可以生成各类统计专题地图图例符号,具有一定的拓展性,促进了统计专题地图制图的自动化。  相似文献   

Combining UAV-based plant height from crop surface models,visible, and near infrared vegetation indices for biomass monitoring in barley     

《International Journal of Applied Earth Observation and Geoinformation》2015

In this study we combined selected vegetation indices (VIs) and plant height information to estimate biomass in a summer barley experiment. The VIs were calculated from ground-based hyperspectral data and unmanned aerial vehicle (UAV)-based red green blue (RGB) imaging. In addition, the plant height information was obtained from UAV-based multi-temporal crop surface models (CSMs). The test site is a summer barley experiment comprising 18 cultivars and two nitrogen treatments located in Western Germany. We calculated five VIs from hyperspectral data. The normalised ratio index (NRI)-based index GnyLi (Gnyp et al., 2014) showed the highest correlation (R² = 0.83) with dry biomass. In addition, we calculated three visible band VIs: the green red vegetation index (GRVI), the modified GRVI (MGRVI) and the red green blue VI (RGBVI), where the MGRVI and the RGBVI are newly developed VI. We found that the visible band VIs have potential for biomass prediction prior to heading stage. A robust estimate for biomass was obtained from the plant height models (R² = 0.80–0.82). In a cross validation test, we compared plant height, selected VIs and their combination with plant height information. Combining VIs and plant height information by using multiple linear regression or multiple non-linear regression models performed better than the VIs alone. The visible band GRVI and the newly developed RGBVI are promising but need further investigation. However, the relationship between plant height and biomass produced the most robust results. In summary, the results indicate that plant height is competitive with VIs for biomass estimation in summer barley. Moreover, visible band VIs might be a useful addition to biomass estimation. The main limitation is that the visible band VIs work for early growing stages only.  相似文献