共查询到16条相似文献，搜索用时 454 毫秒
1.
基于时变地球主惯性矩的三轴地球的自由Euler运动 总被引：3，自引：0，他引：3
在时变地球主惯性矩情形,采用数值方法求解了自由Euler动力学方程和运动学方程.结果表明,地球存在周期约为304.5 d的自由章动;旋转速度的三个分量均出现周期性的增大和减小;地球主惯性矩A、B、C的时变性导致EuIer周期产生复杂的波动,特别是ω3(自转速率)存在周期为22 a、14 a、8 a、4 a、2 a、周年以及更短周期的波动,这表明A、B、C的时变性导致了10 a尺度、周年以及更短周期的日长变化. 相似文献
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陈光华 《测绘与空间地理信息》2009,32(2)
假定地球是一个三轴刚性体,在Euclid空间中做自由旋转.在设定主惯性矩A小于B小于C的情况下,求解欧拉运动方程,得到数值解.计算结果表明:地球在除了自转和自由进动之外,同时还存在着自由章动.章动角会随着时间做周期性变化.重点讨论的是章动角的变化. 相似文献
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针对北斗三号卫星导航系统(BDS-3)五频点观测数据和非差非组合精密定轨理论，介绍了非差非组合观测模型和参数估计方法，提出了利用K均值聚类算法(K-means)进行测站选取的策略，分析并讨论了非差非组合方法的优势.通过K-means和人工经验选取两种测站选取方案，分别使用BDS-3五频，B1C+B2a、B1I+B3I三种频率选择方式，利用30个观测站，对BDS-3中轨道地球卫星(MEO)和倾斜地球同步轨道卫星(IGSO)进行精密定轨处理.结果表明：当接收B1C+B2a频点观测数据测站不足时，非差非组合方法可以通过利用五频观测数据增加观测数据数量、优化测站布局，提高定轨精度，与B1C+B2a频率组合相比，五频定轨结果切向(A)、法向(C)、径向(R)和三维(3D)方向均方根(RMS)月均值分别提升0.003 m、0.004 m、0.003 m和0.007m;K-means算法选取的测站与人工经验选取相比，分布更加合理，定轨精度更高，三种频率选择方案MEO卫星3D RMS月均值精度分别提升0.009 m、0.017 m和0.009 m. 相似文献
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卫星导航信号的非理想性会导致不同接收机之间出现测距偏差,是影响卫星导航系统服务精度和完好性的重要因素。首先,针对北斗系统B1C、B2a新体制信号的非理想性进行分析,利用大口径天线采集了全部北斗三号在轨卫星播发的B1C、B2a信号（共27颗卫星）,评估了不同接收带宽、码鉴相间距下测距偏差的大小与变化特点;然后,以双频多星座星基增强服务应用为例,分析了两个信号在相应接收机中的设计约束条件。研究结果发现,在接收机常用的参数范围内,B1C、B2a信号非理想性引入的测距偏差分别不超过0.68 m、0.44 m;在测距偏差小于0.1 m的性能约束下,B1C、B2a信号可用的约束条件参数范围优于国际民航标准草案中的相关要求。 相似文献
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张瑞华 《解放军测绘研究所学报》2001,21(1):1-5
本文详细讨论了地球自转形变的动力学效应。地球自转形变导数地球引力位系数产生时变摄动并引起测站位置的变化。导出了由于地球自转引起的地球引力位系数变化的表达式，并给出了表示地球自转角速度矢量的三个参数m1、m2、m3与地球自转参数xp、yp、D间的关系。建议在高精度空间大地测量中要顾及由极潮引起的测站位置的变化。 相似文献
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针对月核大小及密度估计问题,利用高分辨率重力场模型GL1500E的二阶位系数和LLR(lunar laser ranging)天平动参数,考虑月核分层为外核和内核的情况,结合非线性粒子群优化算法,对月核大小和组成进行了估计。大批量的统计结果表明,大概率分布的外核半径rc1约为469 km,内核半径rc2约为303 km,外核密度ρc1约为4613 kg/m3,内核密度ρc2约为7004 kg/m3,月幔密度ρm约为3340 kg/m3。月幔密度非常接近地质研究结果3360 kg/m3,内外核半径与近期其他研究结果相近,估算的月核大小与密度组成具有一定的参考价值。若月核由纯铁和硫化亚铁组成,则研究表明,内核大部分由纯铁组成,外核大部分由硫化亚铁组成。 相似文献
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方差分量估计分析北斗伪距信号精度 总被引：2，自引：0，他引：2
针对北斗伪距精度和时间相关性研究较少的问题,该文引入最小二乘方差分量估计方法,对伪距与载波相位形成的电离层残差组合序列求高阶差分,构造伪距观测量的关系方程,并分析了北斗卫星伪距观测量的精度和时间相关性。结果表明,北斗伪距观测量的测量噪声在0.1~0.5m范围内,随高度角的增大而减小;不同频率的伪距噪声各有差异,高度角增大时差异减小,所有测站中B1的伪距噪声最大,B2、B3的大小关系随测站而异;地球同步轨道卫星的伪距精度优于倾斜地球同步轨道和中地球轨道卫星,且后两者差距较小;市场上两款北斗接收机的伪距测量精度相当。相关分析表明,当接收机采样频率等于或低于1Hz时,伪距观测量不存在明显的时间相关性;当采样频率高于1Hz时,伪距观测量表现出较强的时间相关性。 相似文献
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As shown in previous work, dynamical effects of a realistic model of a heterogeneous, compressible, stably stratified liquid
core may be obtained by means of a simple analysis of the generalized two-dimensional Laplace tidal equation which describes
tidal flows of an incompressible and non-gravitating fluid in a thin spherical layer with mobile boundaries. The solution
was presented in the form of expansions in powers of a small parameter κ being the ratio of nutational motion frequency in
space to the frequency of the Earth's diurnal rotation. Whereas in an earlier paper only first-order terms were taken into
account, our present approach includes not only main second-order terms in the spherical harmonic expansions of the solutions,
but also the terms of higher orders. These effects are calculated numerically for realistic models of the Earth's outer liquid
core, solid inner core and anelastic mantle (PREM model). All tables are found in electronic version at http://www.tu-darmstadt.de/fb/vw/ipg/Welcome2.html
Received: 12 June 1997 / Accepted: 11 December 1997 相似文献
13.
The Cartesian moments of the mass density of a gravitating body and the spherical harmonic coefficients of its gravitational
field are related in a peculiar way. In particular, the products of inertia can be expressed by the spherical harmonic coefficients
of the gravitational potential as was derived by MacCullagh for a rigid body. Here the MacCullagh formulae are extended to
a deformable body which is restricted to radial symmetry in order to apply the Love–Shida hypothesis. The mass conservation
law allows a representation of the incremental mass density by the respective excitation function. A representation of an
arbitrary Cartesian monome is always possible by sums of solid spherical harmonics multiplied by powers of the radius. Introducing
these representations into the definition of the Cartesian moments, an extension of the MacCullagh formulae is obtained. In
particular, for excitation functions with a vanishing harmonic coefficient of degree zero, the (diagonal) incremental moments
of inertia also can be represented by the excitation coefficients. Four types of excitation functions are considered, namely:
(1) tidal excitation; (2) loading potential; (3) centrifugal potential; and (4) transverse surface stress. One application
of the results could be model computation of the length-of-day variations and polar motion, which depend on the moments of
inertia.
Received: 27 July 1999 / Accepted: 24 May 2000 相似文献
14.
重力场长周期变化的观测与理论结果比较 总被引：1，自引：0，他引：1
朱耀仲 《武汉大学学报(信息科学版)》2001,26(6):539-543
利用Chandler摆动周期作为约束，估计了地幔滞弹性对地球二阶带谐响应系数κ、带谐位系数J2和卫星轨道升交点Ω的影响，理论预测的长周期潮汐参数被用来与人卫激光测距（SLR）观测结果进行比较。结果表明，SLR确定的长周期潮汐解已能检测到地幔滞弹性的影响。考虑地幔滞弹性和非平衡海洋潮汐效应后，理论预测的18．6a潮汐参数与SLR潮汐解基本相符。 相似文献
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Evolution of the Earth's principal axes and moments of inertia: the canonical form of solution 总被引：4，自引：0，他引：4
Harmonic coefficients of the 2nd degree are separated into the invariant quantitative (the 2nd-degree variance) and the qualitative
(the standardized harmonic coefficients) characteristics of the behavior of the potential V
2(t). On this basis the evolution of the Earth's dynamical figure is described as a solution of the time-dependent eigenvalues–eigenvectors
problem in the canonical form. Such a canonical quadratic form is defined only by temporal variations of the harmonic coefficients
and always remains finite, even within an infinite time interval. An additional condition for the correction or the determination
of temporal variations of the 2nd degree is obtained. Temporal variations of the fully normalized sectorial harmonic coefficients
are estimated in addition to ˙Cˉ
20, ˙Cˉ
21, and ˙Sˉ
21 of the EGM96 gravity model. In addition, a non-linear hyperbolic model for Cˉ
2m
(t), Sˉ
2m
(t) is constructed. The trigonometric form of the hyperbolic model leads to the consideration of the potential V
2(ψ) instead of V
2(t) within the closed interval −π/2≤ψ≤+π/2. Thus, it is possible to evaluate the global trend of V
2(t), the Earth's principal axes and the differences of the moments of inertia within the whole infinite time interval.
Received: 25 September 1998 / Accepted: 28 June 2000 相似文献