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31.
The least-squares ambiguity decorrelation adjustment: its performance on short GPS baselines and short observation spans 总被引：9，自引：2，他引：9
The least-squares ambiguity decorrelation adjustment is a method for fast GPS double-difference (DD) integer ambiguity estimation.
The performance of the method will be discussed, and although it is stressed that the method is generally applicable, attention
is restricted to short-baseline applications in the present contribution. With reference to the size and shape of the ambiguity
search space, the volume of the search space will be introduced as a measure for the number of candidate grid points, and
the signature of the spectrum of conditional variances will be used to identify the difficulty one has in computing the integer
DD ambiguities. It is shown that the search for the integer least-squares ambiguities performs poorly when it takes place
in the space of original DD ambiguities. This poor performance is explained by means of the discontinuity in the spectrum
of conditional variances. It is shown that through a decorrelation of the ambiguities, transformed ambiguities are obtained
which generally have a flat and lower spectrum, thereby enabling a fast and efficient search. It is also shown how the high
precision and low correlation of the transformed ambiguities can be used to scale the search space so as to avoid an abundance
of unnecessary candidate grid points. Numerical results are presented on the spectra of conditional variances and on the statistics
of both the original and transformed ambiguities. Apart from presenting numerical results which can typically be achieved,
the contribution also emphasizes and explains the impact on the method's performance of different measurement scenarios, such
as satellite redundancy, single vs dual-frequency data, the inclusion of code data and the length of the observation time
span.
Received: 31 October 1995 / Accepted: 21 March 1997 相似文献
32.
一种短基线GNSS的三频模糊度解算(TCAR)方法 总被引：3，自引：2，他引：1
TCAR或综合TCAR是GNSS中常用的快速确定三频模糊度的方法,其原理简单,计算方便。根据不同的噪声背景和多径条件,给出综合TCAR单历元实时解算模糊度的误差分析及仿真结果。针对模糊度估计成功概率不高的情况,结合双频相关法(DUFCOM),并根据综合TCAR的特点,对综合TCAR进行改进。最后,将此方法与基于整数最小二乘准则搜索的LAMBDA方法进行比较。仿真结果表明,利用该方法成功搜索到正确模糊度值的概率与LAMBDA方法相当,但降低计算量,有效提高用综合TCAR单历元实时解算模糊度的可靠性。 相似文献
33.
34.
Wind stress fields with high temporal resolution over the North Pacific have been constructured by using ERS-1 scatterometer
data. A simple objective analysis, a successive correction method, was used to construct the fields. Several necessary parameters
used in the method are examined by a simulation based on the climatological data. The meridional decorrelation scale of the
wind stress depends strongly on the season, while the zonal decorrelation scale is highly stable. We determined the decorrelation
scale depending on the location and the time and applied to the successive correction method. The monthly mean field constructed
by averaging the daily mean data is free from an aliasing error, which is a serious problem if a simple monthly averaging
is applied. The daily wind stress data obtained in the present study represent small time- and spatial-scale variation and
large amplitudes compared with data interpolated from simple monthly mean data. The satellite-derived data are also compared
with in situ data obtained by meteorological buoys. The satellite wind speeds are lower than in situ wind speeds for every
buoy. This underestimation is not due to the present objective analysis, but due to the original data, the ERS-1 Scatterometer
Value-Added Product. 相似文献
35.
为解决GNSS模糊度解算中最小二乘模糊度去相关（least-square ambiguity decorrelation adjustment,LAMBDA）算法涉及大量矩阵运算、降相关耗时较长等问题,提出一种对条件方差矩阵进行分块的最小二乘模糊度去相关（blocking in least-square ambiguity decorrelation adjustment,BLAMBDA）算法。该算法对条件方差矩阵进行分块,减少条件方差排序次数,并在此基础上对Cholesky分解公式进行整合,减少Cholesky分解过程中的数乘运算。仿真实验和实测结果表明,与LAMBDA算法相比,BLAMBDA算法的整体解算效率提升显著,且更加稳定。 相似文献
36.
Different image processing algorithms have been evaluated in the context of geological mapping using Landsat TM data. False color composites, the principal component imagery, and IHS decorrelation stretching method for Landsat-5 TM data have been found useful for delineating the regional geological features, mainly to provide the maximum geological information of the studied area. The study testifies that using which image processing yields best results for geological mapping in arid and semiarid regions by preserving morphological and spectral information. Generally, the studied area can be divided into three main geological units: Basaltic intrusive rocks, Metamorphic with varying intensities and Sedimentary rocks. 相似文献
37.
结合星载寄生式干涉合成孔径雷达(InSAR)的工作原理及高稳定频率源的工作特性,给出了时间和频率同步误差模型。基于该误差模型,分析了时间和频率同步误差对干涉相位的影响,首次推导了同步误差导致的信号去相关。基于星载寄生式InSAR系统的空间几何关系和图像信号模型,详细分析了热噪声、模糊、量化噪声、基线、方位向、配准误差及体散射等去相关效应,给出了考虑上述全部去相关因素时系统的相对测高精度,并仿真分析了以Envisat为主星的寄生式InSAR系统在ASAR雷达7个不同波位下的相对测高性能。理论分析和仿真结果表明,在合理选择轨道和雷达参数的前提下,系统可以达到很好的测高精度。 相似文献
38.
On the GPS widelane and its decorrelating property 总被引：2，自引：1，他引：2
P. J. G. Teunissen 《Journal of Geodesy》1997,71(9):577-587
In this contribution we consider the popular widelaning technique from the viewpoint of ambiguity decorrelation. It enables
us to cast the technique into the framework of the least-squares ambiguity decorrelation adjustment (LAMBDA) and to analyse
its relative merits. In doing so, we will provide answers to the following three questions. Does the widelane decorrelate?
Does it explicitly appear in the automated transformation step of the LAMBDA method? Can one do better than the widelane?
It is shown that all three questions can be answered in the affirmative. This holds true for the ionosphere-fixed case, the
ionosphere-float case, as well as for the ionosphere-weighted case.
Received: 11 November 1996 / Accepted: 23 April 1997 相似文献
39.
合成孔径雷达差分干涉测量(Differential Interferometric Synthetic Aperture Radar,DInSAR)在低相关区由于受时间空间去相关的影响,无法得到有效应用。角反射器DInSAR方法能在长时间段内保持幅度和相位稳定性,可以最大程度地减小去相关的影响。但由于反射器在空间上一般形成不规则稀疏网络分布,在平地相位、高程相位计算及相位展开方法上都带来新的挑战。研究三角反射器的DInSAR技术,重点分析基于不规则离散点的最小费用流相位展开算法。对费用流算法权重的选择,通过分析残差的产生来源,提出以弧所穿越的边长度倒数作为弧费用的权重设置方法,解决费用流算法中具有相同费用路径的选择问题。最后将角反射器DInSAR技术应用于滑坡移动的监测,通过对140d时间段的监测,得到与实测值具有较好一致性的结果。 相似文献
40.
Gervasio Degrazia Domenico Anfossi Haroldo Fraga De Campos Velho Enrico Ferrero 《Boundary-Layer Meteorology》1998,86(3):525-534
A new method for deriving the Lagrangian decorrelation time scales for inhomogeneous turbulence is described. The expression for the time scales here derived for the convective boundary layer is compared to those estimated by Hanna during the Phoenix experiment. Then the values of C0, the Lagrangian velocity structure function constant, and of Bi, the Lagrangian velocity spectrum constant, were evaluated from the Eulerian velocity spectra and from the Lagrangian time scales derived, under unstable conditions, from Taylor's statistical diffusion theory. The numerical coefficient of the lateral and vertical Lagrangian spectra in the inertial subrange was found equal to 0.21, in good agreement with previous experimental estimates. 相似文献