GGOS对流层延迟产品精度分析及在PPP中的应用     

姚宜斌  徐星宇  胡羽丰 《测绘学报》2017,46(3):278-287

对流层延迟是卫星导航定位的主要误差源,GNSS广域增强需要高精度的对流层延迟产品进行误差修正。对流层延迟可通过GNSS进行实时估计,也可通过融合多源数据的数值气象预报模型获取。IGS发布的全球对流层天顶延迟产品由GNSS解算,其精度可达4mm,时间分辨率为5min,但其分布不均匀,在广袤的海洋区域无数据覆盖。GGOS Atmosphere基于ECMWF 40年再分析资料,可提供1979年以来时间分辨率为6h、空间分辨率为2.5°×2°的全球天顶对流层总延迟格网数据。本文通过2015年全球IGS测站的ZTD资料对GGOS的ZTD产品进行了评估,研究了GGOS Atmosphere对流层延迟产品与IGS发布ZTD资料之间的系统差,通过线性拟合估计出每个测站GGOS-ZTD与IGSZTD系统差系数(包括比例误差a和固定误差b),然后对比例误差a、固定误差b进行球谐展开,建立了两种ZTD数据源之间的系统差模型。选取IGS测站和陆态网测站,对附加系统偏差改正后的GGOSZTD产品对PPP的收敛速度的影响进行研究。本文研究结果表明:GGOS-ZTD与IGS-ZTD间存在系统偏差,其bias平均为-0.54cm;两者之间较差的RMS平均为1.31cm,说明GGOS-ZTD产品足以满足广大GNSS导航定位用户对对流层延迟改正的需要。将改正了系统差后的GGOS-ZTD产品用于ALBH、DEAR、ISPA测站、PALM测站、ADIS测站、YNMH测站、WUHN测站进行PPP试验,发现可明显提高定位收敛速度,尤其是在U方向上,收敛速度分别提高10.58%、31.68%、15.96%、43.89%、51.46%、14.69%、18.40%。  相似文献   

贵阳市似大地水准面精化项目建设     

石平  裴志刚  娄中军 《测绘与空间地理信息》2016,(4):194-196,200

为解决CORS系统中GNSS高程受技术条件限制精度不高的问题,贵阳市进行了区域似大地水准面精化工作。本文论述了GNSS和水准网的布设及精度,使用了3 877个点重力数据和54个GNSS水准资料,以EIGEN03C地球重力场模型作为参考重力场,由第二类Helmert凝集法完成大地水准面计算,利用球冠谐调和分析方法将GNSS水准与重力似大地水准面联合求解得出的2'!2'格网似大地水准面,在高原高差地区其精度达到"0.010 m。  相似文献   

Spatial and temporal dynamics of bacterial contamination in South France coastal rivers: focus on in‐stream processes during low flows and floods          下载免费PDF全文

Y. Chu  M. G. Tournoud  C. Salles  P. Got  J. L. Perrin  C. Rodier  A. Caro  M. Troussellier 《水文研究》2014,28(8):3300-3313

Faecal indicator bacteria (thermotolerant coliform and faecal streptococci) were enumerated in a Mediterranean coastal river to evaluate bacterial contamination levels in relation to hydrological conditions, to estimate delivery of bacterial loads to transitional and coastal waters (Thau lagoon) and to identify bacterial sources of pollution and their contribution to the bacterial flow. Results showed that (1) in low flow conditions, mean bacterial concentrations were higher than EU guidelines for bathing waters; (2) floods had higher concentrations of indicator bacteria than low flows; (3) low flow conditions represented a negligible proportion of bacterial loads compared with high flow and flood periods; (4) during medium and low flow conditions, bacteria were stored in riverbed fine sediments forming in‐stream stores that may be flushed during floods; (5) the first flush effect was highlighted during an early autumn flood as was the role of in‐stream stores during the course of the flood; and (6) point sources that continuously feed the river are contributing to the pool of bacteria accumulated in the riverbed sediment. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

联合高低卫-卫跟踪和卫星重力梯度数据恢复地球重力场的谱组合法     

钟波  罗志才  李建成  汪海洪 《测绘学报》2012,41(5):735-742

GOCE采用的高低卫-卫跟踪和卫星重力梯度测量技术在恢复重力场方面各有所长并互为补充,如何有效利用这两类观测数据最优确定地球重力场是GOCE重力场反演的关键问题。本文研究了联合高低卫-卫跟踪和卫星重力梯度数据恢复地球重力场的最小二乘谱组合法,基于球谐分析方法推导并建立了卫星轨道面扰动位T和径向重力梯度Tzz、以及扰动位T和重力梯度分量组合{Tzz-Txx-Tyy}的谱组合计算模型与误差估计公式。数值模拟结果表明,谱组合计算模型可以有效顾及各类数据的精度和频谱特性进行最优联合求解。采用61天GOCE实测数据反演的两个180阶次地球重力场模型WHU_GOCE_SC01S（扰动位和径向重力梯度数据求解）和WHU_GOCE_SC02S（扰动位和重力梯度分量组合数据求解）,结果显示后者精度优于前者,并且它们的整体精度优于GOCE时域解,而与GOCE空域解的精度接近,验证了谱组合法的可行性与有效性。  相似文献   

调和常数及深度基准面的变化与历元订正     

暴景阳  许军  崔杨 《海洋测绘》2013,33(3):1-5

分析和验证了黄海沿岸部分长期验潮站M2分潮振幅的线性变化趋势及深度基准面L值增大趋势,发现了长周期分潮调和常数不稳定性对深度基准面确定的影响。研究表明,在剥离了深度基准面变化趋势后,由年观测数据分析结果确定的深度基准面可达到厘米级的精度水平,而由月分析结果确定的深度基准面存在周期性变化,其深度基准面不宜直接计算确定。论证了对潮汐调和常数附加历元信息的必要性和基本方案。通过研究得出对统一深度基准建立的指导性结论。  相似文献   

稳定同位素分馏计算的一个普遍错误   总被引：3，自引：0，他引：3  

刘琪  唐茂  李雪芳  原杰  刘耘 《矿物学报》2009,29(2)

Urey模型(或称Bigeleisen-Mayer公式)是稳定同位素分馏计算的理论基石,它需要使用不同同位素替代后的分子的振动频率来计算两个分子之间的同位素交换反应平衡常数.由于在Urey模型推导过程中使用了简谐振动和刚性转子近似,并利用了同样需要在简谐近似下才成立的Teller-Redlich乘积定则,导致当使用Urey模型时,应该只能使用简谐振动频率.但是,从应用Urey模型进行分馏大小计算的几十年以来,无论Urey或Bigeleisen本人,还是此后众多的研究者都忽略了这个要求.他们要么直接使用光谱数据(真实频率),也就是包含非谐(anharmonicity)贡献后的振动频率,要么使用量子化学方法计算出的简谐振动频率,用校正因子(scaling factor)向真实频率校正.这些做法,不仅不能提高Urey模型的计算精度,反而是造成误差的最主要的原因之一,这是一个历史性的错误.本文通过对Urey模型推导的某些关键步骤的解释,以及对比使用简谐振动频率和含非简谐校正频率的分馏计算结果之间的差别,说明了在Urey模型中必须使用简谐频率的重要性,尤其在量子化学计算已经广泛应用于同位素分馏计算的今天,纠正这种错误,会提高日益增多的这一类计算的精度.  相似文献   

A study of non-linear tidal propagation in shallow inlet/estuarine systems Part II: Theory     

P.E. Speer  D.G. Aubrey 《Estuarine, Coastal and Shelf Science》1985,21(2):207-224

The generation of tidal asymmetries is clarified via numerical integration of the one-dimensional equations for channel geometries characteristic of shallow estuaries. Channels without tidal flats develop a time asymmetry characterized by a longer falling than rising tide. This behavior is enhanced by strong friction and large channel cross-sectional area variability over a tidal cycle. Resulting tidal currents have a shorter, intense flood and a longer, weak ebb (flood-dominant). Addition of tidal flats to the channels can produce a longer rising tide and stronger ebb currents (ebb-dominant), if the area of tidal flats is large enough to overcome the effects of time-variable channel geometry. Weaker friction with flats can also produce this asymmetry.Despite the physical complexity of these systems, essential features of estuarine tidal response can be recovered from one-dimensional models. Shallow estuaries are shown to have a system response leading to stable, uniform senses of tidal asymmetry (either flood- or ebb-dominated, due to phase-locking of forced tidal constituents), with down-channel development in magnitude of asymmetry. These concepts are illustrated by modeling idealized representations of tidal channels at Nauset Inlet, MA, and Wachapreague Inlet, VA, which have flood- and ebb-dominance, respectively.  相似文献   

Analytic signals for multivariate data     

Maurice Craig 《Mathematical Geology》1996,28(3):315-329

Hilbert transformation is a standard tool in univariate signal-processing. It leaves the information content unaffected for, apart from a change of sign, the iterated transform reproduces the original data. As we know from Fourier transforms, such alternative representations of the same information, notwithstanding their theoretical equivalence with the data, can assist powerfully with extracting and interpreting that information. Although the extension to multivariate data is not so obvious for Hilbert as for Fourier transforms, Nabighian gave a treatment of the bivariale situation in 1984. Fueter, some 50 years earlier, had worked on an analogous extension problem, seeking to generalize complex function theory. On comparing these two developments we learn that, although Nabighian's transforms fit naturally into Fueter's theory, they are only one among many alternative possibilities. This paper presents a general theory, of higher dimensional Hilbert transforms and analytic signals, applicable to data of all dimensions less than eight. The change-of-field-direction fillers used in geophysical data processing are shown to arise as special situations.  相似文献   

我国应变固体潮观测及其长时间序列的调和分析结果     

蒋骏  张雁滨  周翠屏 《大地测量与地球动力学》1995,(1)

介绍了我国应变固体潮观测的现状，计算并给出了１９８８年以来我国实际应变固体潮长时间序列的调和分析结果，从资料分析的角度对我国十年来的应变固体潮观测进行了小结。  相似文献   

Stabilized finite elements for harmonic soil dynamics problems near the undrained-incompressible limit     

M. Pastor  Tongchun Li  J.A.Fernández Merodo 《Soil Dynamics and Earthquake Engineering》1997,16(3):161-171

Simple Finite Element models for soil dynamics and earthquake engineering problems in the frequency domain are a fast and valuable tool providing a first approximation before a full non-linear analysis in the time domain is performed.Quite often the problem concerns saturated soils with very small permeability and pore fluid of neglectable compressibility. In the limit, the permeability is assumed to be zero and the pore fluid incompressible. Here, engineers use standard finite element codes formulated in terms of displacements but incompressibility may result in volumetric locking of the mesh with a severe loss of accuracy.The purpose of this paper is to present a simple mixed finite element formulation in the frequency domain based on displacements and pore pressures as main variables. A suitable stabilization technique allowing for equal order interpolation of displacements and pressures has been introduced for incompressible and zero permeability limits.Of course, the range of application is limited to those problems in which the behaviour of the material can be approximated by linear models, and therefore modelling of phenomena such as liquefaction, cyclic mobility or cavitation occur is excluded.The paper shows as well an extremely simple way of coupling solid and water domains as it occurs for instance in quay walls under dynamic loading.  相似文献