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271.
Performance of three types of Stokes's kernel in the combined solution for the geoid 总被引:8,自引:6,他引:2
When regional gravity data are used to compute a gravimetric geoid in conjunction with a geopotential model, it is sometimes
implied that the terrestrial gravity data correct any erroneous wavelengths present in the geopotential model. This assertion
is investigated. The propagation of errors from the low-frequency terrestrial gravity field into the geoid is derived for
the spherical Stokes integral, the spheroidal Stokes integral and the Molodensky-modified spheroidal Stokes integral. It is
shown that error-free terrestrial gravity data, if used in a spherical cap of limited extent, cannot completely correct the
geopotential model. Using a standard norm, it is shown that the spheroidal and Molodensky-modified integration kernels offer
a preferable approach. This is because they can filter out a large amount of the low-frequency errors expected to exist in
terrestrial gravity anomalies and thus rely more on the low-frequency geopotential model, which currently offers the best
source of this information.
Received: 11 August 1997 / Accepted: 18 August 1998 相似文献
272.
闻道秋 《测绘与空间地理信息》1998,(2)
本文讨论了在待定点测站上测量与两已知点的距离和角度进行后方交会坐标计算的原理,并对点位精度和一角一边后方交会多解的判定作了较详细的分析。 相似文献
273.
三部多普勒天气雷达联合测量大气风场的误差分布及最佳布局研究 总被引:17,自引:5,他引:12
从理论上证明了三部多普勒天气雷达联合测量大气风场的误差分布是一组同心圆,同心圆的圆心位置与三部雷达的相对位置和各部雷达的测速精度有关。各种误差分布半径与各部雷达的测速精度和误差的大小有关。如果三部雷达的测速精度相同,联合探测的最佳布局是等边三角形、其边长l与各部雷达的测速精度、要求的探测误差和雷达的最大探测距离(L)有关。当三部多普勒天气雷达的测速精度都是1m/s时,如果要求的探测误差小于或等于2m/s,这时边长与雷达的最大探测距离之间的关系为:l=0.55L。 相似文献
274.
本文指出了福建微震仪地震台网在地震速报和编目工作中存在的主要问题以及问题产生的可能原因;着重阐述了闽台两地区速度模型差异大是造成福建地震台网定位台湾地区震中误差的主原因;最后提出减少震中定位误差的改进办法。 相似文献
275.
J. Marshall 《Journal of Geodesy》2002,76(6-7):334-344
Several pre-analysis measures which help to expose the behavior of L
1 -norm minimization solutions are described. The pre-analysis measures are primarily based on familiar elements of the linear
programming solution to L
1-norm minimization, such as slack variables and the reduced-cost vector. By examining certain elements of the linear programming
solution in a probabilistic light, it is possible to derive the cumulative distribution function (CDF) associated with univariate
L
1-norm residuals. Unlike traditional least squares (LS) residual CDFs, it is found that L
1-norm residual CDFs fail to follow the normal distribution in general, and instead are characterized by both discrete and
continuous (i.e. piecewise) segments. It is also found that an L
1 equivalent to LS redundancy numbers exists and that these L
1 equivalents are a byproduct of the univariate L
1 univariate residual CDF. Probing deeper into the linear programming solution, it is found that certain combinations of observations
which are capable of tolerating large-magnitude gross errors can be predicted by comprehensively tabulating the signs of slack
variables associated with the L
1 residuals. The developed techniques are illustrated on a two-dimensional trilateration network.
Received: 6 July 2001 / Accepted: 21 February 2002 相似文献
276.
水平摆倾斜仪偏离起始平衡面工作时,存在有交互影响,它给观测记录带来误差,从而影响γ因子的精度。本文从理论上论证了交互影响的存在,推导出交互影响的计算公式,总结出消除交互影响的修正方法—组合观测法,并用组合观测法对南昌台倾斜固体潮γ因子的计算进行修正,得到提高γ因子精度的有意义的初步结果。 相似文献
277.
油气勘探的重点正转向复杂地表条件和复杂地质条件的区域.双复杂条件下的叠前深度偏移是解决复杂地表条件和复杂地质构造成像的有效手段.基于“逐步累加”的“直接下延”法是解决复杂地表成像的有效手段,能够较好地消除地形起伏的影响.波动方程频率空间域有限差分(xwfd)叠前深度偏移对介质速度横向变化有较强的适应性,适宜于复杂构造的偏移成像,同其他常规波动方程深度偏移一样,常规的xwfd偏移方法,主要也是针对相位进行波场延拓,没有对振幅做任何处理.我们基于保幅单程波方程,推导出了基于xwfd的保幅波场延拓算子,针对xwfd求解时引入误差的影响,我们在xwfd保幅波场延拓过程中加入了误差补偿,实现了带误差补偿的xwfd保幅偏移.基于带误差补偿的xwfd保幅算子,应用适合起伏地表的直接下延法,对双复杂介质模型和实际资料进行了试算,改善了双复杂介质的成像效果.其中,误差补偿可以在若干个外推步长上进行,所以相对于保幅傅里叶有限差分(ffd)法偏移来说,该方法在改善成像质量的同时,也具有较高的运算效率. 相似文献
278.
279.
Errors in velocities and displacements deduced from accelerographs: An approach based on the theory of error propagation 总被引:3,自引:0,他引:3
Based on the theory of errors, and in particular on the law of error propagation and approximation techniques, we present some simple formulae for random errors of velocities and displacements computed on the basis of numerical integration of accelerometer records. These errors are regarded as function of the characteristic errors of accelerometers and of the duration of the signal for velocities, and of the square of the duration of the signal for displacements. Instabilities in the sampling rate introduce additional noise, which is proportional to the sum of the squares of measurements of acceleration, mostly influenced by high peaks. Because of uneven weighting, however, peaks at early stages of the record are more important than in their later stages. 相似文献
280.