共查询到20条相似文献,搜索用时 15 毫秒
1.
The aim of this investigation is to study how to use a gravimetric(quasi) geoid for levelling by GPS data in an optimal way.The advent of precise geodetic GPS has made the use of a technique possible,which might be called GPS- gravimetric geoid determination.In this approach,GPS heights above the reference ellipsoid are determined for points whose levelled (orthometric) height H is above sea level people have already surveyed;for these points,we thus have the values of the geoid undulation N.These values are then used to constrain the geoid undulations N‘ obtained from the gravimetric solution. 相似文献
2.
利用测区重力点成果及分布较均匀的GPS/水准成果 ,采用重力法及移去~恢复技术 ,确定测区分辨率为 2 .5′× 2 .5′的高精度大地水准面。并由此成果解算GPS网点的正常高 相似文献
3.
GPS水准采用移去恢复技术拟合大地水准面方法的研究 总被引:1,自引:0,他引:1
精化大地水准面是现代重力场和大地测量学工作的重要任务之一。探讨了利用已知水准点上的高程异常拟合区域大地水准面模型时,首先移去EGM96模型计算得到的部分,然后基于移动曲面和多面函数方法分别对剩余高程异常进行拟合,在内插点上再利用EGM96模型把移去的部分恢复,得到该点的高程异常。通过对某局部地区水准点的计算表明,引入EGM96模型的拟合高程异常的精度有所改进,对于大范围地区,这种方法有望能更好地提高大地水准面的拟合精度。 相似文献
4.
5.
In this paper, a number of robust biased estimators (e.g. ordinary robust ridge estimator, robust principal components estimator,
robust combined principal components estimator, robust single-parametric principal components estimator, robust root-root
estimator) are established by means of a unified expression of biased estimators and based on the principle of equivalent
weight. The most attractive advantage of these new estimators is that they can not only overcome the ill-conditioning of the
normal equation but also have the ability to resist outliers. A numerical example is used to illustrate that these new estimators
are much better than the least-squares estimator and various biased estimators even when both ill-conditioning and outliers
exist.
Received: 14 November 1995/Accepted: 11 February 1998 相似文献
6.
Robust estimation of geodetic datum transformation 总被引:17,自引:1,他引:17
Y. Yang 《Journal of Geodesy》1999,73(5):268-274
The robust estimation of geodetic datum transformation is discussed. The basic principle of robust estimation is introduced.
The error influence functions of the robust estimators, together with those of least-squares estimators, are given. Particular
attention is given to the robust initial estimates of the transformation parameters, which should have a high breakdown point
in order to provide reliable residuals for the following estimation. The median method is applied to solve for robust initial
estimates of transformation parameters since it has the highest breakdown point. A smooth weight function is then used to
improve the efficiency of the parameter estimates in successive iterative computations. A numerical example is given on a
datum transformation between a global positioning system network and the corresponding geodetic network in China. The results
show that when the coordinates are contaminated by outliers, the proposed method can still give reasonable results.
Received: 25 September 1997 / Accepted: 1 March 1999 相似文献
7.
GPS网起算点的稳健选择 总被引:3,自引:0,他引:3
对于GPS测量成果转换至地面坐标时的起算点匹配问题,本文提出了利用稳健估计的原理和GPS同本身的内在几何条件和精度信息进行GPS网起算点的选择,在此基础上提出起算点选择的方法。 相似文献
8.
在进行GPS高程拟合时,如果所用函数模型中未知参数个数不恰当,或者随机模型中采用了一个不合理的权阵,都将导致所建数学模型和客观实际存在较大偏差,而影响最终的拟合精度。文中研究了GPS高程拟合时对所建立的数学模型进行参数优化选择和稳健估计,计算数据表明该方法比常规方法在精度上有所提高。 相似文献
9.
On the adjustment of combined GPS/levelling/geoid networks 总被引:12,自引:7,他引:5
A detailed treatment of adjustment problems in combined global positioning system (GPS)/levelling/geoid networks is given.
The two main types of `unknowns' in this kind of multi-data 1D networks are usually the gravimetric geoid accuracy and a 2D
spatial field that describes all the datum/systematic distortions among the available height data sets. An accurate knowledge
of the latter becomes especially important when we consider employing GPS techniques for levelling purposes with respect to
a local vertical datum. Two modelling alternatives for the correction field are presented, namely a pure deterministic parametric
model, and a hybrid deterministic and stochastic model. The concept of variance component estimation is also proposed as an
important statistical tool for assessing the actual gravimetric geoid noise level and/or testing a priori determined geoid
error models. Finally, conclusions are drawn and recommendations for further study are suggested.
Received: 9 September 1998 / Accepted: 8 June 1999 相似文献
10.
定位参数抗差估计的无偏性 总被引:1,自引:0,他引:1
根据抗差估计中误差的最基本假设—对称分布 ,考虑到ρ函数的条件及把反对称估计作为抗差估计计算迭代的初始值 ,验证了定位参数的抗差估计值也一定是反对称估计 ,满足无偏性条件 ,得到定位参数的抗差估计是无偏估计。 相似文献
11.
GPS和GLONASS存在系统差异,组合定位时,采用Helmert方差分量估计可得到更加准确的结果。但GNSS观测值常受到衍射信号和多路径效应的影响,使观测值存有粗差,从而导致Helmert方差分量估计的失真。为此,将抗差Helmert方差分量估计应用于GPS/GLONASS组合单点定位,实验结果表明:抗差Helmert方差分量估计可以有效地抑制组合系统粗差观测值的影响。 相似文献
12.
根据抗差估计中误差的最基本假设一对称分布,考虑到ρ函数的条件及把反对称估计作为抗差估计计算迭代的初始值,验证了定位参数的抗差估计值也一定是反对称估计,满足无偏性条件,得到定位参数的抗差估计是无偏估计. 相似文献
13.
Unification of vertical datums by GPS and gravimetric geoid models with application to Fennoscandia 总被引:3,自引:0,他引:3
The second Baltic Sea Level (BSL) GPS campaign was run for one week in June 1993. Data from 35 tide gauge sites and five
fiducial stations were analysed, for three fiducial stations (Onsala, Mets?hovi and Wettzell) fixed at the ITRF93 system.
On a time-scale of 5 days, precision was several parts in 109 for the horizontal and vertical components. Accuracies were about 1 cm in comparison with the International GPS Geodynamical
Service (IGS) coordinates in three directions. To connect the Swedish and the Finnish height systems, our numerical application
utilises three approaches: a rigorous approach, a bias fit and a three-parameter fit. The results between the Swedish RH70
and the Finnish N 60 systems are estimated to −19.3 ± 6.5, −17 ± 6 and −15 ± 6 cm, respectively, by the three approaches.
The results of the three indirect methods are in an agreement with those of a direct approach from levelling and gravity measurements.
Received: 3 April 1996 / Accepted: 4 August 1997 相似文献
14.
Precision, volume and eigenspectra for GPS ambiguity
estimation based on the time-averaged satellite geometry 总被引:1,自引:1,他引:1
P. J. G. Teunissen 《Journal of Geodesy》1997,71(5):290-301
In this contribution we consider the
time-averaged GPS single-baseline model and study in a qualitative sense its
relation with the geometry-free model and the geometry-based model. The
least-squares estimators of the model are derived and their properties
discussed. Special attention is given to the ambiguity search space, since it
plays such a crucial role in the problem of integer ambiguity estimation and
validation. Easy-to-evaluate, closed-form expressions are presented for the
volumes of the ambiguity search spaces that belong to the geometry-free model,
the single-epoch geometry-based model and the time-averaged model. By means of
an eigenvalue analysis, the geometry of the ambiguity search spaces is revealed
and its impact on the search for the integer least-squares ambiguities
discussed.
Received: 3 April 1996; Accepted: 6 January 1997 相似文献
15.
16.
Pitch and roll attitude estimation of a small-scaled helicopter using single antenna GPS with gyroscopes 总被引:2,自引:2,他引:0
A method is presented for estimating the roll and pitch attitude of a small-scaled unmanned helicopter based on the velocity
measurements of the global positioning system (GPS). The small-scaled helicopter is a radio controlled (RC) model which is
readily available and affordable for academic laboratories as a research platform. Only one single antenna GPS receiver is
equipped on the RC helicopter to acquire the velocity measurements needed for the attitude estimation. The velocity information
is recorded by the onboard computer for post-processing. An attitude and heading reference system (AHRS) is used to provide
the reference attitudes. The required angular rates and heading for this study are also given by the gyroscopes and compass
of the AHRS for the sake of system’s simplification. The Kalman filter is applied to estimate the helicopter’s accelerations
by using the GPS velocity measurements. The estimated accelerations form the fundamental elements of synthesizing the pseudo-roll
and the pseudo-pitch. With some legitimate simplifications and assumptions, the relation between the helicopter’s attitudes
and the accelerations estimated from the GPS velocity measurements can be developed. Furthermore, to enhance the accuracy
of the pseudo-attitudes, the angular rates acquired from the gyroscopes are incorporated into the estimation algorithm of
pseudo-attitudes by using a complementary filter.
相似文献
Fei-Bin HsiaoEmail: |
17.
Improving the orbit estimates of GPS satellites 总被引:2,自引:2,他引:0
The Extended Center for Orbit Determination in Europe (CODE) Orbit Model, an empirical orbit model proposed by Beutler and
colleagues in 1994, has been tested extensively since January 1996. Apart from six osculating Keplerian elements, this orbit
model consists of nine (instead of the conventional two) parameters to take into account the deterministic part of the force
field acting on the satellites. Based on the test results an improved orbit parameterization is proposed. The new orbit parameterization
consists of the conventional two parameters plus three additional parameters, a constant and two periodic terms (a cosine
and a sine term), in the X-direction to model the effects of the solar radiation pressure. Results based on one full year of routine orbit estimation,
using the original and the new orbit parameterization, are presented to demonstrate the superiority of the new approach. An
improvement of the orbit estimates with at least a factor of two is observed!
Received: 20 January 1998 / Accepted: 30 November 1998 相似文献
18.
粗差检测与抗差估计相结合的方法在动态相对定位中的应用 总被引:2,自引:0,他引:2
分析了粗差对GPS动态相对定位的影响,给出了相应的影响函数和抗差估计方法。建议采用粗差探测与抗差估计相结合的方法来处理GPS动态定位中的粗差问题。抗差估计中的等价权分别采用了IGG3方案和双因子等价权函数,对两种方案的效果进行比较和分析,并利用实测数据对所提方法的实际效果进行了检验。结果表明,基于粗差探测和抗差估计相结合的粗差处理方法可有效控制和抵御粗差的影响;分别采用IGG3方案和双因子等价权函数的定位结果差异较小。 相似文献
19.
在利用多站GPS数据建立电离层延迟模型时,将卫星硬件延迟和接收机硬件延迟作为整体参数求解并剔除会产生与实际不符的情况,因此将二者分离是十分必要,笔者给出了最优信息扩散估计与广义逆结合分离硬件延迟的基本方法,并结合实例对该方法进行了探讨. 相似文献
20.
短程精密测距精度一般优于GNSS测量精度,工程中常用GNSS测量与精密测距方法联合建立高精度工程测量控制网,对两者所存在的尺度差异,常采用尺度比进行统一,其关键是尺度比的合理选择。文中参照精密测距边长确定的实测尺度比相对于理论尺度比的残差,建立空间分布与尺度残差线性关系,对尺度差异进行估计并确定合理的尺度比,再在投影层面将尺度比等价转换成参考椭球参数进行数据归算,从而实现GNSS与精密测距成果的高度融合,得到高精度工程测量控制网的可靠成果。 相似文献