共查询到20条相似文献，搜索用时 163 毫秒
1.
用强制改正法建立中国近海平均海平面高模型 总被引：1，自引：0，他引：1
联合Geosat GM数据、ERS-1数据、T/P数据、T/P新轨道数据、ERS-2数据和GFO数据,采用强制改正法确定了中国近海(0°~41°N,105°~132°N)2′×2′格网分辨率的平均海面高模型,并将其与CLS01、GF-SC00.1和KMS04平均海面高模型进行了比较。统计结果显示,这些模型格网差值的RMS分别是10.17cm1、2.70 cm和16.13 cm,在剔除差值大于50 cm(分别剔除0.5%、0.89%和1.6%)的误差点后,RMS分别为7.98 cm1、0.29 cm和12.59 cm;与三年的Jason-1数据(Cycle 22~127)的平均框架相比,其RMS为7.40cm。 相似文献
2.
3.
卫星测高数据的沿轨迹重力异常反演法及其应用 总被引：10，自引：0，他引：10
本文给出了一套基于直角坐标系下的垂线偏差求解重力异常公式 ,并将之发展成为一套新的沿轨迹重力异常求解公式。与其他方法相比 ,本方法无须求解交叠点处沿轨迹和跨轨迹方向的海面高斜率 ,仅需计算沿轨迹方向的海面高斜率 ,因而更为简洁、有效 ,而且分辨率可以更高并可与真正的沿航迹实际船测重力相比较、验证。据此 ,利用 Geosat/GM、ERS-1 /35天及TOPEX/Poseidon三种测高数据 ,反演了南中国海域 (0°～ 2 5°N,1 0 5°～ 1 2 2°E)的 2′× 2′重力异常—— IGG-S。通过与实际船测资料和国际同行提供的重力模型相比 ,IGG-S总体精度达到1 0× 1 0 - 5ms- 2。 相似文献
4.
以反解 Stokes公式为数学模型 ,应用由 T/ P测高数据计算的大地水准面高反演了海域平均重力异常 ,并与船测平均重力异常和 OSU91A位模型计算的平均重力异常进行了比对分析 ,得出了一些有益的结论。 相似文献
5.
重力异常作为地球重力场的一种基本指标,广泛应用于大地测量、地球物理、地质、地震与海洋领域。为了快速获取高精度的未知点重力异常,本文基于EIGEN-6C4重力场模型解算某110 km×110 km区域内重力异常,构建5′×5′的重力异常格网模型,结合格网节点数据采用6种不同的插值算法拟合未知点的重力异常,最后使用外部检核的方法评价插值算法的精度。实验结果表明,6种插值算法的拟合精度均达到4 mgal以内,自然三次样条法和反距离加权插值法拟合精度最高,得到精度达到2.7 magl的重力异常。 相似文献
6.
渤海湾航空重力及其在海域大地水准面精化中的应用 总被引：1，自引：1，他引：0
近海航空重力数据在陆海大地水准面统一中起着重要作用。近3年来,利用我国首套航空重力测量系统(CHAGS)完成了渤海湾地区近20万平方千米的5′×5′格网平均重力异常数据的获取。本文首先介绍了渤海湾地区航空重力测量的概况,给出航空重力测量数据的处理要点;然后,详细讨论了航空重力测量的精度评估方法,其中针对该区域的测线布设特点,提出了"重叠格网比较法"以评估格网平均重力异常的内符合精度。结果表明,对于5′的波长分辨率,交叉点重力异常不符值在抗差后的中误差约为1.5 mGal,重叠格网法获得的5′×5′格网平均重力异常的中误差约为1.6 mGal;5′×5′格网重力异常与卫星测高和船测重力的比较精度优于3.0mGal;由航空重力测量获得的1°×1°格网平均重力异常与GOCE卫星重力位模型的计算值相比较,其系统性差异小于0.5 mGal、中误差约为2.7 mGal。利用航空重力数据后,渤海湾区域大地水准面与16个GPS水准点的比较精度由EGM2008模型的约23 cm提高到约12 cm。 相似文献
7.
联合多种测高资料和Geosat/GM波形重构数据,基于EIGEN_CG01C重力场模型,采用沿轨迹加权最小二乘方法和逆Vening-Meinesz公式,确定了中国海及其邻域1.5′×1.5′重力异常。将计算结果与最新船测资料进行了比较,标准差为3.37×10-5m.s-2。 相似文献
8.
以拟合方差最小为准则,通过点质量法拟合船载重力测量数据,得到点质量大小、埋深等参数。回避点质量法数值求解的不稳定性问题,借鉴移去-恢复技术的思路,利用该参数计算船载重力测量点上的重力异常,并将其在测线上的重力异常中扣除,计算出船载重力残差值。以点质量大小、埋深等参数计算卫星测高重力格网点上重力异常,同样得到测高重力残差值。采用加权最小曲率格网化方法,将船载重力残差值与测高重力残差值格网化,进而恢复由点质量大小、埋深等参数计算格网点处的重力异常,实现卫星测高与船载重力测量数据融合。经国际船载重力测量数据检核,融合后的模型较国际船载重力测量数据的平均偏差在1~2 mGal（1 Gal=1×10-2 m/s2）,标准差约为4 mGal。本文的研究方法可为陆地、海岸带区域的多种重力数据的融合、航空重力及卫星重力的向下延拓等问题提供参考。 相似文献
9.
本文提出了处理卫星重力梯度数据以确定高分辩力重力场模型的单层位法并对其中的独立估计法进行了误差分析，数字结果显示：当卫星高度为200km，卫星数据网格宽度为15′，卫星重力梯度数据的精度为2×10~(-3)E时，利用独立估计法可得到分辩力为1°×1°（100km）的全球重力场模型，其重力异常精度小于1（mgal）；若卫星高度降至160km，卫星重力梯度数据的精度达到3×10~(-4)E，则获得的重力场模型的分辩力可提高到0.5°×0.5°（50km），其重力异常精度仍小于1（mgal）。 相似文献
10.
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
11.
Analysis of some systematic errors affecting altimeter-derived sea surface gradient with application to geoid determination over Taiwan 总被引：3，自引：1，他引：3
C. Hwang 《Journal of Geodesy》1997,71(2):113-130
This paper analyzes several systematic errors affecting sea surface gradients derived from Seasat, Geosat/ERM, Geosat/GM,
ERS-1/35d, ERS-1/GM and TOPEX/POSEIDON altimetry. Considering the data noises, the conclusion is: (1) only Seasat needs to
correct for the non-geocentricity induced error, (2) only Seasat and Geosat/GM need to correct for the one cycle per revolution
error, (3) only Seasat, ERS-1/GM and Geosat/GM need to correct for the tide model error; over shallow waters it is suggested
to use a local tide model not solely from altimetry. The effects of the sea surface topography on gravity and geoid computations
from altimetry are significant over areas with major oceanographic phenomena. In conclusion, sea surface gradient is a better
data type than sea surface height. Sea surface gradients from altimetry, land gravity anomalies, ship gravity anomalies and
elevation data were then used to calculate the geoid over Taiwan by least-squares collocation. The inclusion of sea surface
gradients improves the geoid prediction by 27% when comparing the GPS-derived and the predicted geoidal heights, and by 30%
when comparing the observed and the geoid-derived deflections of the vertical. The predicted geoid along coastal areas is
accurate to 2 cm and can help GPS to do the third-order leveling.
Received 22 January 1996; Accepted 13 September 1996 相似文献
12.
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
13.
A technique is presented for the development of a high-precision and high-resolution mean sea surface model utilising radar
altimetric sea surface heights extracted from the geodetic phase of the European Space Agency (ESA) ERS-1 mission. The methodology
uses a cubic-spline fit of dual ERS-1 and TOPEX crossovers for the minimisation of radial orbit error. Fourier domain processing
techniques are used for spectral optimal interpolation of the mean sea surface in order to reduce residual errors within the
initial model. The EGM96 gravity field and sea surface topography models are used as reference fields as part of the determination
of spectral components required for the optimal interpolation algorithm. A comparison between the final model and 10 cycles
of TOPEX sea surface heights shows differences of between 12.3 and 13.8 cm root mean square (RMS). An un-optimally interpolated
surface comparison with TOPEX data gave differences of between 15.7 and 16.2 cm RMS. The methodology results in an approximately
10-cm improvement in accuracy. Further improvement will be attained with the inclusion of stacked altimetry from both current
and future missions.
Received: 22 December 1999 / Accepted: 6 November 2000 相似文献
14.
Aliasing of the diurnal and semi-diurnal tides is a major problem when estimating the ocean tides from satellite altimetry.
As a result of aliasing, the tides become correlated and many years of altimeter observations may be needed to seperate them.
For the three major satellite altimetry missions to date i.e., GEOSAT, ERS-1, and TOPEX/POSEIDON (T/P), the alias periods
as well as the Rayleigh periods over which the tides decorrelate can be identified. Especially in case of GEOSAT and ERS-1,
severe correlation problems arise. However, it is shown by means of covariance analyses that the tidal phase advance differences
on crossing satellite groundtracks can significantly reduce the correlations among the diurnal and semi-diurnal tides and
among these tides and the seasonal cycles of ocean variability. Therefore, it has been attempted to solve a multi-satellite
response tidal solution for the diurnal and semi-diurnal bands from a total of 7 years of altimetry. Unfortunately, it could
be shown that the GEOSAT and ERS-1 orbit errors are too large to improve a 3-year T/P tidal solution with about 2 years of
GEOSAT and 2 years of ERS-1 altimeter observations. However, these results are preliminary and it is expected that more accurate
orbits, which have become available recently for ERS-1, and additional altimeter data from ERS-2 and the GEOSAT Follow-On
(GFO) should lead to an improved T/P tidal model.
Received: 4 May 1999 / Accepted: 24 January 2000 相似文献
15.
Global mean sea surface heights (SSHs) and gravity anomalies on a 2′×2′ grid were determined from Seasat, Geosat (Exact Repeat Mission and Geodetic Mission), ERS-1 (1.5-year mean of 35-day, and
GM), TOPEX/POSEIDON (T/P) (5.6-year mean) and ERS-2 (2-year mean) altimeter data over the region 0∘–360∘ longitude and –80∘–80∘ latitude. To reduce ocean variabilities and data noises, SSHs from non-repeat missions were filtered by Gaussian filters
of various wavelengths. A Levitus oceanic dynamic topography was subtracted from the altimeter-derived SSHs, and the resulting
heights were used to compute along-track deflection of the vertical (DOV). Geoidal heights and gravity anomalies were then
computed from DOV using the deflection-geoid and inverse Vening Meinesz formulae. The Levitus oceanic dynamic topography was
added back to the geoidal heights to obtain a preliminary sea surface grid. The difference between the T/P mean sea surface
and the preliminary sea surface was computed on a grid by a minimum curvature method and then was added to the preliminary
grid. The comparison of the NCTU01 mean sea surface height (MSSH) with the T/P and the ERS-1 MSSH result in overall root-mean-square
(RMS) differences of 5.0 and 3.1 cm in SSH, respectively, and 7.1 and 3.2 μrad in SSH gradient, respectively. The RMS differences
between the predicted and shipborne gravity anomalies range from 3.0 to 13.4 mGal in 12 areas of the world's oceans.
Received: 26 September 2001 / Accepted: 3 April 2002
Correspondence to: C. Hwang
Acknowledgements. This research is partly supported by the National Science Council of ROC, under grants NSC89-2611-M-009-003-OP2 and NSC89-2211-E-009-095.
This is a contribution to the IAG Special Study Group 3.186. The Geosat and ERS1/2 data are from NOAA and CERSAT/France, respectively.
The T/P data were provided by AVISO. The CLS and GSFC00 MSS models were kindly provided by NASA/GSFC and CLS, respectively.
Drs. Levitus, Monterey, and Boyer are thanked for providing the SST model. Dr. T. Gruber and two anonymous reviewers provided
very detailed reviews that improved the quality of this paper. 相似文献
16.
Johannes Bouman 《Journal of Geodesy》2012,86(4):287-304
The vertical gradients of gravity anomaly and gravity disturbance can be related to horizontal first derivatives of deflection
of the vertical or second derivatives of geoidal undulations. These are simplified relations of which different variations
have found application in satellite altimetry with the implicit assumption that the neglected terms—using remove-restore—are
sufficiently small. In this paper, the different simplified relations are rigorously connected and the neglected terms are
made explicit. The main neglected terms are a curvilinear term that accounts for the difference between second derivatives
in a Cartesian system and on a spherical surface, and a small circle term that stems from the difference between second derivatives
on a great and small circle. The neglected terms were compared with the dynamic ocean topography (DOT) and the requirements
on the GOCE gravity gradients. In addition, the signal root-mean-square (RMS) of the neglected terms and vertical gravity
gradient were compared, and the effect of a remove-restore procedure was studied. These analyses show that both neglected
terms have the same order of magnitude as the DOT gradient signal and may be above the GOCE requirements, and should be accounted
for when combining altimetry derived and GOCE measured gradients. The signal RMS of both neglected terms is in general small
when compared with the signal RMS of the vertical gravity gradient, but they may introduce gradient errors above the spherical
approximation error. Remove-restore with gravity field models reduces the errors in the vertical gravity gradient, but it
appears that errors above the spherical approximation error cannot be avoided at individual locations. When computing the
vertical gradient of gravity anomaly from satellite altimeter data using deflections of the vertical, the small circle term
is readily available and can be included. The direct computation of the vertical gradient of gravity disturbance from satellite
altimeter data is more difficult than the computation of the vertical gradient of gravity anomaly because in the former case
the curvilinear term is needed, which is not readily available. 相似文献
17.
Procedures to calculate mean sea surface heights and gravity anomalies from altimeter-derived sea surface heights and along-track
sea surface slopes using the least-squares collocation procedure are derived. The slope data is used when repeat track averaging
is not possible to reduce ocean variability effects. Tests were carried out using Topex, Geosat, ERS-1 [35-day and 168-day
(2 cycle)] data. Calculations of gravity anomalies in the Gulf Stream region were made using the sea surface height and slope
data. Tests were also made correcting the sea surface heights for dynamic ocean topography calculated from a degree 360 expansion
of data from the POCM-4B global ocean circulation model. Comparisons of the anomaly predictions were carried out with ship
data using anomalies calculated for this paper as well as others.
Received: 19 August 1996 / Accepted: 14 April 1997 相似文献
18.
Christopher Jekeli 《Journal of Geodesy》1983,57(1-4):10-28
The problem of the divergence of the geopotential spherical harmonic series at the earth's surface is investigated from a numerical, rather than a theoretical, approach. A representative model of the earth's potential is devised on the basis of a density layer, which, in the spherical approximation, generates a gravity field whose harmonic constituents decay according to an accepted degree variance model. This field, expanded to degree 300, and a topographic surface specified to a corresponding resolution of 67 km are used to compute the differences between truncated inner and outer series of the gravity and height anomalies at the surface of the earth model. Up to degree 300, these differences attain RMS values from 0.33 μgal to 86 μgal for the gravity anomaly and from 0.32 μm to 410 μm for the height anomaly, in areas ranging respectively from near the equator to the vicinity of the pole. In addition to these values, there is an expected truncation effect, caused by the neglect of higher degree components of the inner series, of about 30 mgal and 36 cm, respectively. The field is then subjected to a Gaussian filter which effectively cuts off information at degree 300 (at the 5% level). The RMS error to degree 300 is thereby reduced by factors of 10 to 20, with a concomitant reduction in the truncation effect to about 0.3 mgal and 0.7 cm. 相似文献
19.
海面高度作为最重要的海洋物理参数之一,在预防海啸、风暴潮中起到重要作用,是海洋科学,遥感测绘领域的重要研究内容之一。粗糙度作为影响海面测高精度的重要因素之一,主要是由风速变化引起,本文为了探究风速引起的粗糙度变化对海面测高精度的影响,分别进行了湖面实验与海面实验。通过对风速与反射信号相位差RMS关系的研究,定性分析了粗糙度对测高精度的影响,结果表明,在反射信号相位差RMS增加0.005(单位rad)时,测高的误差RMS增加了近一倍。 相似文献
20.
联合TOPEX/Poseidon与Geosat/ERM测高资料建立区域潮汐模型的研究 总被引：2，自引：1，他引：2
利用近十年的T/P测高数据来反演南海(8°~23°N,109°~120°E)九个主要分潮的潮汐参数,并计算了Geosat/ERM卫星对应的各主分潮的混叠周期及Rayleigh周期。根据潮汐参数提取的要求,选取了7个主分潮,为了克服混叠影响,将T/P沿迹点处的主要分潮间的5组差比关系引入到Geosat沿迹点处,并利用T/P提供的Sa模型去除Sa对M2的扰动影响。精度估计的结果表明,Geosat/ERM反演的潮汐参数的精度与传统的月分析结果的精度相近;因差比关系的捆绑,整个全日和半日潮族迟角偏差相近,这主要和Geosat/ERM的轨道设计有关。本文的方法可以应用于利用轨道调整后的T/P卫星的测高数据提取潮汐参数。 相似文献