Effects of errors-in-variables on weighted least squares estimation   总被引：2，自引：1，他引：1  

Peiliang Xu  Jingnan Liu  Wenxian Zeng  Yunzhong Shen 《Journal of Geodesy》2014,88(7):705-716

Although total least squares (TLS) is more rigorous than the weighted least squares (LS) method to estimate the parameters in an errors-in-variables (EIV) model, it is computationally much more complicated than the weighted LS method. For some EIV problems, the TLS and weighted LS methods have been shown to produce practically negligible differences in the estimated parameters. To understand under what conditions we can safely use the usual weighted LS method, we systematically investigate the effects of the random errors of the design matrix on weighted LS adjustment. We derive the effects of EIV on the estimated quantities of geodetic interest, in particular, the model parameters, the variance–covariance matrix of the estimated parameters and the variance of unit weight. By simplifying our bias formulae, we can readily show that the corresponding statistical results obtained by Hodges and Moore (Appl Stat 21:185–195, 1972) and Davies and Hutton (Biometrika 62:383–391, 1975) are actually the special cases of our study. The theoretical analysis of bias has shown that the effect of random matrix on adjustment depends on the design matrix itself, the variance–covariance matrix of its elements and the model parameters. Using the derived formulae of bias, we can remove the effect of the random matrix from the weighted LS estimate and accordingly obtain the bias-corrected weighted LS estimate for the EIV model. We derive the bias of the weighted LS estimate of the variance of unit weight. The random errors of the design matrix can significantly affect the weighted LS estimate of the variance of unit weight. The theoretical analysis successfully explains all the anomalously large estimates of the variance of unit weight reported in the geodetic literature. We propose bias-corrected estimates for the variance of unit weight. Finally, we analyze two examples of coordinate transformation and climate change, which have shown that the bias-corrected weighted LS method can perform numerically as well as the weighted TLS method.  相似文献   

基于层次分析法的缅甸矿业投资风险分析     

王珍  林刚  李增  赵明东 《国土资源情报》2014,(8):31-35

随着我国综合国力和国际竞争力的加强,越来越多的中国企业走出国门,进入国外的矿产资源投资市场。但是,由于各国的矿业政策法规频繁调整,矿产资源对外投资不确定性增加,使得中国企业参与全球矿产资源配置的风险持续扩大。另外,矿业项目投资风险在矿业项目投资的筹划、实施过程中是客观存在的。风险分析是矿业项目评估的重要内容之一。本文采用层次分析法对影响矿业投资的各个风险因素进行了分析评价,以便企业可以对缅甸投资环境有较好的了解,更好地参与缅甸的矿产市场投资。  相似文献   

省直管市（县）体制下建设用地监管技术研究   总被引：1，自引：0，他引：1  

曾乙洪  阳雄伟  韩智  涂炎钦 《国土资源信息化》2014,(6):29-34

面向解决省直体制下市（县）建设用地管理业务监管难度大问题,研究建设用地全过程监管关键技术,设计该模式下的监管模式、技术架构、业务模型和数据模型,实现省直管市（县）模式下的建设用地批前、批中、批后＂批-供-用-补-查-登＂全过程监管。  相似文献   

Path-finding through flexible hierarchical road networks: An experiential approach using taxi trajectory data     

Qingquan Li  Zhe Zeng  Tong Zhang  Jonathan Li  Zhongheng Wu 《International Journal of Applied Earth Observation and Geoinformation》2011

Optimal paths computed by conventional path-planning algorithms are usually not “optimal” since realistic traffic information and local road network characteristics are not considered. We present a new experiential approach that computes optimal paths based on the experience of taxi drivers by mining a huge number of floating car trajectories. The approach consists of three steps. First, routes are recovered from original taxi trajectories. Second, an experiential road hierarchy is constructed using travel frequency and speed information for road segments. Third, experiential optimal paths are planned based on the experiential road hierarchy. Compared with conventional path-planning methods, the proposed method provides better experiential optimal path identification. Experiments demonstrate that the travel time is less for these experiential paths than for paths planned by conventional methods. Results obtained for a case study in the city of Wuhan, China, demonstrate that experiential optimal paths can be flexibly obtained in different time intervals, particularly during peak hours.  相似文献   

对测绘成果档案管理工作的思考     

邓建强  曾洪周 《国土资源信息化》2011,(1):45-48

测绘成果档案是各级测绘部门在测绘工作中形成的具有保存价值的基础测绘成果,成果管理工作具有非常重要的意义。随着现代科学技术的发展,电子数据逐步被数字测绘成果所取代,因此对测绘成果档案的管理提出了新的要求。目前测绘成果档案管理存在诸多问题。本文在分析这些问题的基础上提出当前测绘成果档案工作管理对策。  相似文献   

中国北方不同气候区晴天陆面过程区域特征差异   总被引：5，自引：0，他引：5  

曾剑  张强  王胜 《大气科学》2011,35(3):483-494

采用2008年7～9月份观测的中国干旱-半干旱区实验观测协同与集成研究资料,将我国北方干旱一半干旱区根据气候类型和地理位置划分为西北干旱区、黄土高原区和东北冷区三个区域,分析了干旱-半干旱区陆面热量平衡和辐射平衡日变化的区域差异.结果显示:不同气候区域的地表辐射和能量过程差异明显,而这种差异主要源于大气和土壤中可利用水...  相似文献   

东南沿海地区降水与全球海温变化的关系   总被引：1，自引：0，他引：1  

郑益群  高俊岭  熊琳峰  曾新民 《气象科技》2011,39(6):772-778

为了解近50年来东南沿海地区降水与海温变化的关系,对该地区降水与全球海表温度进行了奇异值分解（SVD）。结果表明：印度洋、南海及赤道东太平洋地区是对东南沿海地区降水有影响的关键区域。东南沿海地区秋冬季的降水总体上来说对前期海温变化的响应不敏感,而东南沿海地区夏季降水受前期海温的影响较为明显,尤其是上年夏季北印度洋、南海地区海温的变化对当年降水有明显影响。因此,在预测东南沿海地区夏季降水时应该重点考虑上年夏季北印度洋及南海地区海温的变化情况。  相似文献   

基于GIS的小麦赤霉病气象等级预报系统的设计与实现   总被引：2，自引：1，他引：1  

周元  李轩  高苹  张旭晖  曾明剑 《气象科技》2011,39(3):379-384

以江苏省为例,介绍了基于地理信息系统的小麦赤霉病气象等级预报系统的设计思路及核心技术。系统采用VB.Net 2005和ArcEngine做为开发平台,基于MSSQL SERVER 2005数据库查询,利用日平均相对湿度、日平均气温和日照时数3个气象要素,用两种算法来计算小麦赤霉病发生发展的气象等级,生成包含地理信息的文字产品和图形产品,实现了小麦赤霉病气象等级业务预报。系统具有功能强大,算法高效,操作简单等特点,解决了业务部门资料分析处理和赤霉病气象等级预报的相关问题,具有很好的业务应用和推广价值。  相似文献   

长江三角洲近46 a气温和降水的变化趋势   总被引：2，自引：2，他引：0       下载免费PDF全文

潘敖大  王珂清  曾燕  谢志清  苗茜 《大气科学学报》2011,34(2):180-188

利用长江三角洲地区84个气象站观测数据,分析了长江三角洲1961—2006年气温和降水的时空变化趋势。结果表明,46 a间长江三角洲地区年平均气温上升趋势显著,冬季平均气温的增温幅度最大,春、秋次之。增温显著区域与城市带分布区域吻合。极端最低气温有明显上升,而年极端低温事件日数的下降趋势显著。部分地区的极端最高气温呈上升趋势,在城市密集带尤为突出。年降水量没有明显的变化趋势,但降水的季节分配有所变化,冬、夏季降水量呈现显著上升趋势,秋季降水量明显下降,春季没有明显变化。  相似文献   

SHRIMP zircon U–Pb and molybdenite Re–Os isotopic dating of the tungsten deposits in the Tianmenshan–Hongtaoling W–Sn orefield, southern Jiangxi Province, China, and geological implications     

Chengyou Feng  Zailin Zeng  Dequan Zhang  Wenjun Qu  Andao Du  Daxin Li  Hongquan She 《Ore Geology Reviews》2011,43(1):8-25

The southern Jiangxi Province is a major part of the Nanling W–Sn metallogenic province of southern China, where all W–Sn ore deposits are temporally and spatially related to Mesozoic granitic intrusions. The Tianmenshan–Hongtaoling orefield is a recently explored territory endowed by several styles of W–Sn mineralization. The orefield comprises three composite granitic plutons: Tianmenshan, Hongtaoling and Zhangtiantang associated with several tens of W–Sn-polymetallic ore deposits (Maoping, Baxiannao, Niuling, Zhangdou, Yaolanzhai and others) along their contacts. In this study, four new SHRIMP zircon U–Pb ages were determined for three composite granitic plutons, and 33 molybdenite samples from five W–Sn deposits were analysed by ICP-MS Re–Os isotopic method. SHRIMP zircon U–Pb ages for both medium to coarse-gained biotite granite and porphyritic biotite monzogranite from the Tianmenshan composite pluton are 157.2 ± 2.2 Ma and 151.8 ± 2.9 Ma, respectively. Molybdenite Re–Os isochron ages for the related Baxiannao fracture-controlled tungsten deposits are 157.9 ± 1.5 Ma. Maoping greisens-type tungsten deposits were emplaced at 155.3 ± 2.8 Ma and the Maoping wolframite–quartz veins at 150.2 ± 2.8 Ma, respectively. The SHRIMP U–Pb age of zircons from the Hongtaoling biotite granite is 151.4 ± 3.1 Ma whereas the molybdenite Re–Os isochron ages of the genetically related Niuling endocontact tungsten quartz veins and Zhangdou exocontact tungsten quartz veins are 154.9 ± 4.1 to 154.6 ± 9.7 Ma and 149.1 ± 7.1 Ma, respectively. The SHRIMP zircon U–Pb age of the Zhangtiantang fine-grained muscovite granite is 156.9 ± 1.7 Ma, whereas the molybdenite Re–Os isochron age for the related Yaolanzhai greisens-type tungsten deposit is 155.8 ± 2.8 Ma. These new age data, combined with those available from the literature, indicate that the ages of W–Sn ores and related granites are Late Jurassic with a peak at 150 to 160 Ma, which corresponds to the widespread Mesozoic metallogenic event in southern China. Molybdenites from this group of tungsten deposits have quite low Re contents (29.1 to 2608 ppb), suggesting continental crustal provenance of the ore metals.  相似文献