共查询到18条相似文献，搜索用时 890 毫秒
1.
本文利用Topex/Poseidon卫星测高资料,从快速Hartley变换(FHT)基本概念入手,给出了Hotine公式在平面近似、球面近似、Molodenskii近似下,反演中国近海海洋重力的数学模型。另对FHT处理中所需的坐标转换以及边缘效应等问题进行了讨论。同时,为了改善长波特性的重力场信息,引入了M阶次的OSU91A参考重力场对上述Molodenskii模型进行了改化。 相似文献
2.
在应用快速Hartly变换(FHT)或快速Fourier变换(FFT)计算Stokes积分公式时,总是先将Stokes 公式化成卷积形式,然后用 FHT或 FFT完成卷积运算,从而避免了复杂费时的积分计算。但由于 Stokes公式不严格满足卷积定义,欲将其化成卷积形式必须作一些近似。这种近似虽能在一定精度范围满足要求,但对于高精度要求仍有不能允许的计算误差。本文建议采用球面坐标转换方法,能有效地消除无论是用 FHT或 FFT 计算Stokes 积分卷积化所带来的误差影响。 相似文献
3.
本文从函数模型和随机模型两方面入手综合讨论大地测量混合边值问题及其解。函数模型方面，首先对混合边值问题进行了一般描述；继而分别建立了垂直边值和水平边值问题的二阶近似模型；随机模型方面，考虑到重力场的随机模型与随机观测量及其重力场本身的随机性有关，任何假设的理想模型都可能偏离实际模型。故文章中介绍了能抵制随机模型偏差影响的抗差估计原理。如果将重力场看成随机场，则建议采用抗差拟合推估解。 相似文献
4.
本文利用Ｔｏｐｅｘ／Ｐｏｓｅｉｄｏｎ卫星测高资料,从快速Ｈａｒｔｌｅｙ交换（ＦＨＴ）基本概念入手,给出了Ｈｏｔｉｎｅ公式在平面近似、球面近似、Ｍｏｌｏｄｅｎｓｋｉｉ的 下,反演中国近海海洋重力的数学模型,另对ＦＨＴ处理中所需的坐标转换以及边缘效应等问题进行了讨论。同时,为改善长波特性的重力场信息,引入了Ｍ阶次的ＯＳＵ９１Ａ参考重力场对上述Ｍｏｌｏｄｅｎｓｋｉｉ模型进行了改化。 相似文献
5.
新近月球重力场模型的比较与分析 总被引：1，自引：0，他引：1
针对以往和新近高阶月球重力场模型,利用多种方式分析和比较了不同重力场模型的功率谱和自由空气重力异常,仿真计算了不同高度、不同倾角、不同重力场模型对探月卫星轨道演化的影响。所有重力场模型对近极轨卫星轨道的影响相同,均适用于近极轨卫星的精密定轨。CEGM02、SGM100h、SGM150较适用于非极轨绕月卫星的精密定轨。未来探月活动可以考虑发射非极轨卫星,进一步完善月球重力场模型。在月球重力场全球模型的基础上,使用局部球谐函数方法,可以对局部重力场进行补充,以完善全球重力场模型。 相似文献
6.
不同月球重力场模型的比较与分析 总被引：1，自引：0，他引：1
针对3个不同时期解算的月球重力场模型特点,对重力场模型的功率谱和地形相关性进行了分析。基于LP150Q、SGM100i和GL0660B月球自由空气重力异常的比较,研究分析了月球重力场的特征。结果表明,所有的重力场模型都能很好地反映月球正面的重力场特征。基于星间Ka波段测速数据解算的GRAIL系列模型不仅分辨率得到了较大的提高,而且能更好地反映月球背面的重力场信息。 相似文献
7.
8.
月球重力场可用来研究月球演化过程和内部结构,是影响绕月卫星精密定轨的重要因素。基于GRAIL任务数据解算的GL0660B重力场模型,极大提高了月球重力场空间频谱信号的强度和范围。本文首先通过计算相应重力场的阶方差和地形相关性分析,对GL0660B模型进行了精度分析;其次,利用GL0660B模型和其他几个月球重力场模型进行比较,对月球重力场的特征进行了分析;然后通过绘制GL0660B模型和LP150Q模型在月球外部不同高度处的重力异常图,分析比较了月球重力场模型在不同高度上所反映的月球重力场的特征和差异;最后,利用GEODYN软件模拟计算了不同高度卫星的轨道变化。可以看出绕月卫星离心率随时间的变化,以及周期性变化趋势,而且不同高度卫星轨道处质量瘤的摄动影响不同,远月点、近月点和偏心率的变化也存在差异。 相似文献
9.
10.
地球重力场位系数模型可以用于计算局部重力扰动场元。然而随着地球重力场模型阶次的提高、局域重力场计算范围的增大,其计算速度往往不能满足工程需求。针对这一问题,在对位系数模型泰勒级数展开的基础上提出了采用向量运算、混合编程的方法,同时对连带勒让德函数Belikov递推方法中与经纬度无关的量进行了预先计算,有效提高了计算速度。提出的方法对于利用超高阶次重力场模型快速解算大范围、高分辨率重力场元数据以及累加求和计算具有一定的参考与借鉴意义。 相似文献
11.
本文提出了利用快速Hartley变换(FHT)计算Stokes公式的方法,这一算法最适合于用来计算实序列的积分变换,而快速Fourier变换(FFT)较适合于用来计算复序列的积分变换。计算Stokes公式只涉及实序列问题,用FHT计算Stokes公式比用FFT算法更有效。本文详细地描述了用FHΥ计算Stokes公式的算法,进行了数值计算,与相应的FFT计算结果作了比较。结果表明,两种算法可以得到相同的精度,但是,FHT的计算速度比FFT的计算速度快一倍以上,且所需要的内存空间只是后者的一半。 相似文献
12.
M. E. Ayhan 《Journal of Geodesy》1997,71(6):362-369
In the analyses of 2D real arrays, fast Hartley (FHT), fast T (FTT) and real-valued fast Fourier transforms are generally
preferred in lieu of a complex fast Fourier transform due to the advantages of the former with respect to disk storage and
computation time. Although the FHT and the FTT in one dimension are identical, they are different in two or more dimensions.
Therefore, first, definitions and some properties of both transforms and the related 2D FHT and FTT algorithms are stated.
After reviewing the 2D FHT and FTT solutions of Stokes' formula in planar approximation, 2D FHT and FTT methods are developed
for geoid updating to incorporate additional gravity anomalies. The methods are applied for a test area which includes a 64×64
grid of 3′×3′ point gravity anomalies and geoid heights calculated from point masses. The geoids computed by 2D FHT and FTT are found to
be identical. However, the RMS value of the differences between the computed and test geoid is ±15 mm. The numerical simulations
indicate that the new methods of geoid updating are practical and accurate with considerable savings on storage requirements.
Received: 15 February 1996; Accepted: 22 January 1997 相似文献
13.
利用Poisson积分推导Hotine函数及Hotine公式应用问题 总被引：2，自引：0，他引：2
给出一种直接利用改进的Poisson积分确定Hotine函数的推导 ,其中不包括函数的零阶和一阶项。讨论了Hotine公式在陆地和海洋局部重力场逼近中的应用问题。 相似文献
14.
NING JinshengLI JianchengCHAO DingboNING Jinsheng Academician Professor School of Geo-science Surveying Engineering WTUSM Wuhan China 《地球空间信息科学学报》1998,(1)
This paper presents a method for the computation of the Stokes for-mula using the Fast Hartley Transform（FHT）techniques.The algorithm is mostsuitable for the computation of real sequence transform,while the Fast FourierTransform（FFT）techniques are more suitable for the computaton of complex se-quence transform.A method of spherical coordinate transformation is presented inthis paper.By this method the errors,which are due to the approximate term inthe convolution of Stokes formula,can be effectively eliminated.Some numericaltests are given.By a comparison with both FFT techniques and numerical integra-tion method,the results show that the resulting values of geoidal undulations byFHT techniques are almost the same as by FFT techniques,and the computation-al speed of FHT techniques is about two times faster than that of FFT techniques. 相似文献
15.
Geoid and quasigeoid modelling from gravity anomalies by the method of least squares modification of Stokes’s formula with additive corrections is adapted for the usage with gravity disturbances and Hotine’s formula. The biased, unbiased and optimum versions of least squares modification are considered. Equations are presented for the four additive corrections that account for the combined (direct plus indirect) effect of downward continuation (DWC), topographic, atmospheric and ellipsoidal corrections in geoid or quasigeoid modelling. The geoid or quasigeoid modelling scheme by the least squares modified Hotine formula is numerically verified, analysed and compared to the Stokes counterpart in a heterogeneous study area. The resulting geoid models and the additive corrections computed both for use with Stokes’s or Hotine’s formula differ most in high topography areas. Over the study area (reaching almost 2 km in altitude), the approximate geoid models (before the additive corrections) differ by 7 mm on average with a 3 mm standard deviation (SD) and a maximum of 1.3 cm. The additive corrections, out of which only the DWC correction has a numerically significant difference, improve the agreement between respective geoid or quasigeoid models to an average difference of 5 mm with a 1 mm SD and a maximum of 8 mm. 相似文献
16.
Estimation of dynamic ocean topography in the Gulf Stream area using the Hotine formula and altimetry data 总被引：3，自引：2，他引：1
Changyou Zhang 《Journal of Geodesy》1998,72(9):499-510
Two modifications of the Hotine formula using the truncation theory and marine gravity disturbances with altimetry data are
developed and used to compute a marine gravimetric geoid in the Gulf Stream area. The purpose of the geoid computation from
marine gravity information is to derive the absolute dynamic ocean topography based on the best estimate of the mean surface
height from recent altimetry missions such as Geosat, ERS-1, and Topex. This paper also tries to overcome difficulties of
using Fast Fourier Transformation (FFT) techniques to the geoid computation when the Hotine kernel is modified according to
the truncation theory. The derived absolute dynamic ocean topography is compared with that from global circulation models
such as POCM4B and POP96. The RMS difference between altimetry-derived and global circulation model dynamic ocean topography
is at the level of 25cm. The corresponding mean difference for POCM4B and POP96 is only a few centimeters. This study also
shows that the POP96 model is in slightly better agreement with the results derived from the Hotine formula and altimetry
data than POCM4B in the Gulf Stream area. In addition, Hotine formula with modification (II) gives the better agreement with
the results from the two global circulation models than the other techniques discussed in this paper.
Received: 10 October 1996 / Accepted: 16 January 1998 相似文献
17.
In the numerical evaluation of geodetic convolution integrals, whether by quadrature or discrete/fast Fourier transform (D/FFT) techniques, the integration kernel is sometimes computed at the centre of the discretised grid cells. For singular kernels—a common case in physical geodesy—this approximation produces significant errors near the computation point, where the kernel changes rapidly across the cell. Rigorously, mean kernels across each whole cell are required. We present one numerical and one analytical method capable of providing estimates of mean kernels for convolution integrals. The numerical method is based on Gauss-Legendre quadrature (GLQ) as efficient integration technique. The analytical approach is based on kernel weighting factors, computed in planar approximation close to the computation point, and used to convert non-planar kernels from point to mean representation. A numerical study exemplifies the benefits of using mean kernels in Stokes’s integral. The method is validated using closed-loop tests based on the EGM2008 global gravity model, revealing that using mean kernels instead of point kernels reduces numerical integration errors by a factor of ~5 (at a grid-resolution of 10 arc min). Analytical mean kernel solutions are then derived for 14 other commonly used geodetic convolution integrals: Hotine, Eötvös, Green-Molodensky, tidal displacement, ocean tide loading, deflection-geoid, Vening-Meinesz, inverse Vening-Meinesz, inverse Stokes, inverse Hotine, terrain correction, primary indirect effect, Molodensky’s G1 term and the Poisson integral. We recommend that mean kernels be used to accurately evaluate geodetic convolution integrals, and the two methods presented here are effective and easy to implement. 相似文献
18.
李叶才 《武汉大学学报(信息科学版)》1989,(1)
本文通过对Hotine积分和Stokes积分进行比较,指出Hotine积分是一种更有利于确定高精度大地水准面的方法,同时还导出了计算Hotine积分中截断系数的递推公式以及高阶截断误差的近似估计公式。 相似文献