共查询到18条相似文献，搜索用时 125 毫秒
1.
从快速 Hartley变换 (FHT)基本概念入手 ,给出了 Hotine核在平面近似、球面近似、Molodenskii近似下的反演模型。另对 FHT处理中所需的坐标转换以及边缘效应等问题加以讨论。同时 ,为了改善长波特性的重力场信息 ,利用 M阶次的参考重力场对上述 Molo-denskii模型进行了改化。 相似文献
2.
无论是Stokes理论、Molodenskii理论还是Bjerhammar理论,均不能根据给定边值(即给定地球表面的重力位或重力)求出外部重力场精确解。Stokes理论以大地水准面为边界,需要对大地水准面外部的物质(质量)进行调整,但我们不 相似文献
3.
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
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.
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
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7.
多元化重力场信息系统构建 总被引：1，自引：0，他引：1
基于重力测量信息化建设的目的,在对重力场信息深入分析的基础上对多元化重力场信息服务及其应用进行了研究。建立了以多元化重力场信息为基础,集数据存储、处理、分发和应用于一体的服务体系。研究结果表明,构建基于多元化重力场信息数据库的重力场信息服务系统,能够使海量重力场信息的管理更科学、使用更高效、空间分布特性表现更直观;满足了重力场研究和应用部门的数据服务要求;实现了海量重力数据获取、处理和管理的自动化;提高了工作效率。 相似文献
8.
卫星重力梯度向下延拓的谱方法 总被引：7，自引：0，他引：7
本文提出在平面近似下解算卫星重力梯度向下延拓问题的谱方法，并采用模拟数据进行了试算，结果表明该方法是有效的。这为利用卫星重力梯度数据精化局部重力场提供了可供参考的方法。 相似文献
9.
球近似下地球外空间任意类型场元的地形影响 总被引：1，自引：0，他引：1
传统的重力归算方法只适用于地球表面上的重力异常,不能用于扰动重力、垂线偏差、重力梯度等其他类型扰动重力场元,不适合处理除地面外其他高度上场元的地形影响问题。当前,地球重力场探测的场元类型越来越丰富,探测的高度也逐渐转向航空和卫星高度,精确处理地球外空间各种类型重力场元的地形影响已成为地球重力场领域面临的重要课题。本文通过直接分解由地形生成的具有调和性质的引力场,从而导出地球外空间任意高度、任意类型扰动重力场元的地形影响,在此基础上给出在球近似下地形影响的严密算法和高精度快速算法。利用本文推荐的地形影响计算方案,可以方便地处理各种类型地面重力、海洋重力、航空重力、卫星重力、卫星测高数据的地形影响,从而丰富重力场数据处理的内涵,改善地球重力场算法的性能。 相似文献
10.
陆地重力精化技术是精确重力场信息、提供重力场应用保障的关键技术手段.介绍了陆地重力精化技术软件平台的设计思想和主要功能并对各部分涉及的关键技术进行了分析与阐述.软件平台由重力场数据处理、重力场数据应用与分析以及重力场数据可视化3部分组成.实现了重力观测数据的数据库管理,重力场数据处理的自动化,野外重力测量布点仿真和重力场信息的图形可视化等功能. 相似文献
11.
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
12.
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
13.
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
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