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1.
Validating ocean tide loading models using GPS 总被引：3，自引：0，他引：3
Ocean tides cause periodic deformations of the Earths surface, also referred to as ocean tide loading (OTL). Tide-induced displacements of the Earths crust relying on OTL models are usually taken into account in GPS (Global Positioning System) data analyses. On the other hand, it is also possible to validate OTL models using GPS analyses. The following simple approach is used to validate OTL models. Based on a particular model, instantaneous corrections of the site coordinates due to OTL are computed. Site-specific scale factors, f, for these corrections are estimated in a standard least-squares adjustment process of GPS observations together with other relevant parameters. A resulting value of f close to unity indicates a good agreement of the model with the actual site displacements. Such scale factors are computed for about 140 globally distributed IGS (International GPS Service) tracking sites. Three OTL models derived from the ocean tide models FES95.2.1, FES99, and GOT00.2 are analyzed. As expected, the most reliable factors are estimated for sites with a large loading effect. In general, the scaling factors have a value close to unity and no significant differences between the three ocean tide models could be observed. It is found that the validation approach is easy to apply. Without requiring much additional effort for a global and self-consistent GPS data analysis, it allows detection of general model misfits on the basis of a large number of globally distributed sites. For detailed validation studies on OTL models, the simultaneous estimation of amplitudes and phases for the main contributing partial tides within a GPS parameter adjustment process would provide more detailed answers. 相似文献
2.
In recent years, ocean tide loading displacements (OTLD) have been measured using the Global Positioning System (GPS) and
Very Long Baseline Interferometry (VLBI). This study assesses the accuracy of GPS measurements of OTLD by comparison with
VLBI measurements and estimates derived from numerical ocean tide models. A daily precise point positioning (PPP) analysis
was carried out on ∼11 years of GPS data for each of 25 sites that have previous OTLD estimates based on data from co-located
VLBI sites. Ambiguities were fixed to integer values where possible. The resulting daily estimates of OTLD, at eight principal
diurnal and semi-diurnal tidal frequencies, were combined to give GPS measurements of OTLD at each site. The 3D GPS and VLBI
measurements of OTLD were compared with estimates computed (by convolution with Green’s functions) from five modern ocean
tide models (CSR4.0, FES2004, GOT00.2, NAO99b and TPXO6.2). The GPS/model agreement is shown to be similar to the VLBI/model
agreement. In the important radial direction, the GPS/model misfit is shown to be smaller than the VLBI/model misfit for seven
of the eight tidal constituents; the exception being the K2 constituent. Fixing of GPS carrier-phase ambiguities to integer
values resulted in a marginal improvement to the GPS/model agreement. Statistically, it is shown there is no significance
to the difference between the fit of the GPS and VLBI measurements of OTLD to modelled values. Equally, differences in fit
of either the complete set of GPS or VLBI estimates to the five sets of model-derived values cannot be identified with statistical
significance. It is thus concluded that, overall, we cannot distinguish between GPS and VLBI measurements of OTLD, and that
at the global scale, present ocean tide models are accurate to within the current measurement noise of these techniques. 相似文献
3.
在高精度GPS数据处理中,海潮的影响是一个不可忽略的因素。利用GAMIT软件解算2011年东南极沿海地区中国中山站及其周边6个IGS站的GPS数据,对比分析了FES2004、DTU10、EOT11a、GOT4.7、HAMTIDE11a、OSU12以及TPXO7.2等7个全球海潮模型在不同测站的海潮负荷差异,比较了海潮负荷对于GPS基线解的影响。结果表明,海潮负荷对GPS基线解的影响与测站所处位置及基线方位有关,达到cm级,相对影响达到10-8,因此,在高精度的GPS基线解算中必须考虑海潮的影响;但选用不同海潮模型对东南极沿海地区GPS基线解算的差异可忽略不计。 相似文献
4.
Estimates of ocean tide loading displacements and its impact on position time series in Hong Kong using a dense continuous GPS network 总被引：1，自引：0，他引：1
Three-dimensional ocean tide loading (OTL) displacements of eight diurnal and semidiurnal constituents at 12 sites in Hong
Kong were estimated using 3–7 years of continuous global positioning system (GPS) observations. OTL displacements were estimated
using the precise point positioning (PPP) technique on a daily basis and then combined. The OTL displacements obtained by
GPS were compared with predictions using seven recent global ocean tide models. The effect of OTL displacements on GPS position
time series was also investigated. The study shows that the GPS-derived OTL displacements (excluding K1 and K2 constituents)
agree best with those predicted by the GOT4.7 and NAO99b models. The GPS/model agreement is generally at the sub-millimeter
level, except for S2, K1, and K2 constituents with relatively large errors. After systematic biases between the GPS and model
values are removed, the misfits of all sites for M2, S2, N2, O1, P1, and Q1 are less than 0.5 and 1.0 mm in the horizontal
and vertical components, respectively, while larger misfits (within 2.5 mm) are observed for K1 and K2. Integer ambiguity
fixing slightly improves the east component of OTL displacement estimates. The study also finds that GPS-derived OTL corrections,
instead of model predicts, can be used in daily data processing with the exception of K1 and K2. Including K2 corrections,
a secular vertical rate of up to 1 mm/year in position time series can be induced, which needs to be confirmed by further
studies. 相似文献
5.
利用GPS技术反演海潮负荷信息，相比传统重力及甚长基线干涉测量，有着全球覆盖、测站数多、全天候、成本低等诸多优势，为海潮模型的建立提供了有效的技术手段，也对海潮负荷效应的研究有着重要的理论意义和参考价值。利用动态精密单点定位技术（precise point positioning，PPP）反演海潮负荷位移，同时构建了区域海潮负荷位移模型。利用香港连续运行参考站8 a的GPS观测数据，精密测定了11个测站的三维海潮负荷位移参数，与高精度海潮模型提供的海潮负荷位移参数进行比较，发现除K2、K1潮波外，其他潮波的均方根误差均小于2 mm。与已有的动态PPP及静态PPP结果对比发现，采用改进的重叠时段动态PPP算法可有效改善K1潮波的反演精度；该方法反演的海潮负荷位移精度可达到静态PPP反演海潮负荷位移的精度，且对于K1潮波，在东西方向，动态PPP算法的反演精度较静态PPP略有改善。利用最小二乘曲面拟合法可有效建立中国香港地区GPS区域海潮负荷位移模型，可有效弥补沿海地区因验潮站稀少而导致的海潮模型适应性差的问题。 相似文献
6.
利用动态PPP对香港12个GPS测站2007—2012年的数据反演了海潮负荷位移,通过与7个全球海潮模型、1个区域模型和静态PPP反演的结果比较发现,相对于另外几个模型,动态PPP反演结果与TPXO.7.2、EOT11a、HAMTIDE和NAO99Jb模型的结果符合得更好。与静态PPP的结果比较发现其RMS与各模型的RMS大体上一致,只是在S2、K2和K1的E方向和M2、S2的N方向稍有增加。此外,除K2和K1潮波外,动态PPP与模型的RMS值在水平方向上均小于1 mm,在垂直方向上均小于2.5 mm,能达到和静态PPP相当的精度。本文反演的结果与NAO99Jb模型值存在明显的系统偏差,当去除系统偏差后,所有潮波的RMS值都有明显的减小,尤其在K1的垂直方向RMS从16.4 mm减少到1.3 mm。此外,通过将香港2012年验潮站数据反演的潮波参数与模型的结果进行比较发现,其结果同样与TPXO.7.2、EOT11a、HAMTIDE和NAO99Jb这4个模型更为符合,这进一步验证了动态PPP反演海潮的有效性,同时说明这4个模型比较适合香港区域。 相似文献
7.
受特殊海岸线及复杂海底地形的影响,目前发布的全球海潮模型在局部沿海地区差异较大,需利用其他大地测量手段直接测定沿海地区的海潮负荷位移参数。GPS技术因具有全天候、精度高、成本低等优势,已成为获取海潮负荷位移参数的有效手段。本文基于GPS技术监测测站三维位移变化的灵敏度高于监测48个海潮参数的灵敏度这一基本思想,改进了利用GPS精密单点定位(PPP)技术估计48个海潮调和参数的方法,直接逐历元求解三维海潮负荷位移变化,再利用调和分析方法提取主要潮波(M2、S2、N2、K2、K1、O1、P1、Q1)的海潮负荷位移建模参数(振幅与相位)。利用12个香港连续运行参考站(CORS)8年的GPS观测数据,计算各测站的海潮负荷位移建模参数。与传统方法比较,本文方法可有效加速K1潮波在东西方向的收敛。将GPS海潮负荷位移建模参数估值与中国近海海潮模型值比较,发现除S2、K2和K1潮波的均方根误差较大外,其他潮波的均方根误差均小于1.5mm。将香港2008—2014年验潮站数据反演的潮波参数与海潮模型值比较,结果表明:GPS与验潮站数据反演的潮波参数均与中国近海海潮模型及HAMTIDE2011.11A全球海潮模型符合较好,验证了GPS PPP反演海潮负荷位移的有效性。采用GPS PPP估计的8个潮波的振幅与相位值替换全球海潮模型中对应的潮波值,进行海潮负荷效应改正,可减弱GPS长时间序列中的半周年信号。 相似文献
8.
Determination of the free core nutation period from tidal gravity observations of the GGP superconducting gravimeter network 总被引：1，自引：1，他引：1
This study is based on 25 long time-series of tidal gravity observations recorded with superconducting gravimeters at 20 stations
belonging to the Global Geodynamic Project (GGP). We investigate the diurnal waves around the liquid core resonance, i.e.,
K
1, ψ1 and φ1, to determine the free core nutation (FCN) period, and compare these experimental results with models of the Earth response
to the tidal forces. For this purpose, it is necessary to compute corrected amplitude factors and phase differences by subtracting
the ocean tide loading (OTL) effect. To determine this loading effect for each wave, it was thus necessary to interpolate
the contribution of the smaller oceanic constituents from the four well determined diurnal waves, i.e., Q
1, O
1, P
1, K
1. It was done for 11 different ocean tide models: SCW80, CSR3.0, CSR4.0, FES95.2, FES99, FES02, TPXO2, ORI96, AG95, NAO99
and GOT00. The numerical results show that no model is decisively better than the others and that a mean tidal loading vector
gives the most stable solution for a study of the liquid core resonance. We compared solutions based on the mean of the 11
ocean models to subsets of six models used in a previous study and five more recent ones. The calibration errors put a limit
on the accuracy of our global results at the level of ± 0.1%, although the tidal factors of O
1 and K
1 are determined with an internal precision of close to 0.05%. The results for O
1 more closely fit the DDW99 non-hydrostatic anelastic model than the elastic one. However, the observed tidal factors of K
1 and ψ1 correspond to a shift of the observed resonance with respect to this model. The MAT01 model better fits this resonance shape.
From our tidal gravity data set, we computed the FCN eigenperiod. Our best estimation is 429.7 sidereal days (SD), with a
95% confidence interval of (427.3, 432.1). 相似文献
9.
World-wide synthetic tide parameters for gravity and vertical and horizontal displacements 总被引：3，自引：0，他引：3
The response of the Earth’s crust to the direct effect of lunisolar gravitational forcing is known as the body tide. The body tide is superimposed by surface-loading forces due to the pressure of the periodically varying ocean tide acting on the Earth, called ocean tide loading (OTL). Both body tide and OTL can be decomposed into components of the same frequency known as tidal parameters. However, OTL is more complicated than body tides because of the dynamic effects of the ocean. Estimating OTL requires a model of the ocean tides and knowledge of the elastic properties of the solid Earth. Thus, synthetic tide parameters (amplitude factors and phase leads) have been developed here on a world-wide grid for gravity and positional displacements. The body tide contributions were added to the oceanic contribution to provide the Earth tide response. The accuracy and reliability of the synthetic tidal parameters have been estimated by comparing observed gravity and vertical-displacement tide parameters with those interpolated from our synthetic model, which shows good agreement. Tests also indicate that the synthetic tide parameters provide realistic gravimetric and displacements for practical use in tidal prediction. 相似文献
10.
Stavros A. Melachroinos Jean-Michel Lemoine Paul Tregoning Richard Biancale 《Journal of Geodesy》2009,83(10):915-923
Unmodeled sub-daily ocean S2 tide signals that alias into lower frequencies have been detected in the analysis of gravity recovery and climate experiment
(GRACE) space gravity fields of GRGS. The most significant global S2 aliased signal occurs off the northwest coast of Australia in a shallow continental shelf zone, a region with high tidal
amplitudes at a period of 161 days. The GRACE S2 aliased equivalent water height grids are convolved with Green’s functions to produce GRACE aliased tidal loading (GATL)
vertical displacements. The analysis of hourly global positioning system (GPS) vertical coordinate estimates at permanent
sites in the region confirms the presence of spectral power at the S2 frequency when the same ocean tide model (FES2004) was used. Thus, deficiencies in the FES2004 ocean tide model are detected
both directly and indirectly by the two independent space geodetic techniques. Through simulation, the admittance (ratio of
amplitude of spurious long-wavelength output signal in the GRACE time-series to amplitude of unmodeled periodic signals) of
the GRACE unmodeled S2 tidal signals, aliased to a 161-day period, is found to have a global average close to 100%, although with substantial spatial
variation. Comparing GATL with unmodeled S2 tidal sub-daily signals in the vertical GPS time-series in the region of Broome in NW Australia suggests an admittance of
110–130%. 相似文献
11.
利用验潮站资料的中国近岸海潮模型精度评估 总被引：1，自引：0，他引：1
针对全球海潮模型在我国近海海域精度较差的问题,该文采用中国沿岸30个长期验潮站的调和常数,对比了3种全球海潮模型DTU10、TPXO7.2、NAO.99b和1个区域海潮模型NAO.99Jb在中国沿岸的准确度。通过海潮模型与验潮站分潮的振幅中误差、迟角中误差以及8个主要分潮的预报误差,对渤海、黄海、东海和南海北部进行了详细的分析。结果表明,NAO.99Jb在中国海域精度最高,NAO.99b次之。在渤海海域,DTU10在Q_1分潮精度最高,NAO.99b在K2分潮精度最高,其余分潮均是NAO.99Jb精度最高;在黄海海域,NAO.99b在Q_1分潮精度最高,其余分潮均是NAO.99Jb精度最高;在东海海域,DTU10在Q_1分潮精度最高,TPXO7.2在P1精度最高,NAO.99Jb在O1、M2分潮精度最高,其余分潮均是NAO.99b精度最高;在南海北部海域,DTU10在N2、S2分潮精度最高,其余分潮均是NAO.99Jb精度最高。 相似文献
12.
Crustal deformations caused by surface load due to ocean tides are strongly dependent on the surface load closest to the observation site. In order to correctly model this ocean loading effect near irregular coastal areas, a high-resolution coastline is required. A test is carried out using two GPS sites located in Alaska, where the ocean tide loading effect is large and consequently observed easily by relative positioning with GPS. The selected sites are Fair (Fairbanks) and Chi3 (located on an island that separates Prince William Sound from the Gulf of Alaska). Processing of hourly baseline solutions between Fair and Chi3 over a period of 49 days yields a significant ocean tide loading effect. The data are processed using different strategies for the tropospheric delay correction. However, the best results are obtained when 1-h ZTD (Zenith Tropospheric Delay) parameters for hourly solutions are used. In this case ocean tide loading is not absorbed into the ZTD parameters. Hence, ocean tide loading can be well resolved in the GPS data analysis. In addition, the M
2 ocean tide wave in the Gulf of Alaska has a very large amplitude. Although the horizontal M
2 ocean tide loading amplitude in general is only about 1/4 of the vertical M
2 ocean tide loading amplitude, the differential horizontal M
2 ocean tide loading displacements are nevertheless measurable using differential GPS (DGPS). When using the GOT99.2 ocean tide model and taking the coastal structure into account, the predicted differential vertical M
2 amplitude and Greenwich phase lag due to ocean tide loading are 19.3 mm and 110.2 degrees respectively, while GPS measurements yield 21.3 ± 1.0 mm and 99.7±2.8 degrees. Similarly, the predicted differential horizontal M
2 amplitude and Greenwich phase lag (in the north–south direction) are 4.5 mm and –77.0 degrees, while GPS yields 5.4 ± 0.3 mm and –106.3±3.3 degrees. Only the north-south component of the differential horizontal M
2 ocean tide loading wave is considered, because the east–west component is too small for the processed baseline and not detectable using DGPS. 相似文献
13.
针对全球海潮模型在不同沿海地区存在差异性以及在中国近海精度不高的问题,利用全球海潮模型FES2004和NAO99b计算上海地区(经纬度范围为120.85°E～122.2°E,30.6667°N～31.8833°N)S2、M2、K1和O1四个分潮的海潮负荷位移在垂直分量上的差异;并利用中国近海模型osu.chinasea.2010对全球海潮模型FES2004中相应的区域进行替换,计算近海效应对SHJZ站(上海金山)、SHJBS站(上海宝山)、SHAO站(上海佘山)以及DCMD站(上海崇明)四个测站精密定位的影响。结果表明:1) 全球海潮模型FES2004和NAO99b在上海地区存在较明显的差异,尤其是垂直分量,最大接近4 mm,且两个模型的差异随离海洋距离增大而减小;2) 利用修正前后的全球海潮模型FES2004经过计算分析得出,近海效应对上海地区GPS测站精密定位的影响达到5 mm,对测站垂直分量的位移影响从大到小分别是DCMD站(5.1 mm)、SHBS站(4.9 mm)、SHJS(4.2 mm)、SHAO(3.6 mm)。 相似文献
14.
The accuracy of ocean tide loading (OTL) displacement values has long been assumed to be dominated by errors in the ocean
tide models used, with errors due to the convolution scheme used considered very small (2–5%). However, this paper shows that
much larger convolution errors can arise at sites within approximately 150 km of the coastline, depending on the method used
to refine the discrete regularly spaced grid cells of the ocean tide model to better fit the coastline closest to the site
of interest. If the local water mass redistribution approach is implemented, as used in the OLFG/OLMPP software recommended
in the IERS 2003 conventions, OTL height displacement errors of up to around 20% can arise, depending on the ocean tide model
used. Bilinear interpolation only, as used in the SPOTL and CARGA softwares for example, is shown from extensive global and
regional comparisons of OTL displacement values derived from the different methods and softwares to be more appropriate. This
is verified using GPS observations. The coastal refinement approach used in the OLFG/OLMPP software was therefore changed
in August 2007 to use bilinear interpolation only. It is shown that with this change, OTL displacement values computed using
OLFG/OLMPP, SPOTL and CARGA invariably agree to the millimetre level for coastal sites, and better than 0.2 mm for sites more
than about 150 km inland. 相似文献
15.
利用T/P测高数据反演了中国近海及西北太平洋海域的潮汐参数,构造了CSR3.0、FES95.2和T/P反演的海潮模型改正下的海面高时间序列,通过海面高变化曲线及功率谱的比较确定了利用测高数据发现的海平面季节内变化主要是潮汐模型误差的贡献. 相似文献
16.
采用FARRELL的负荷理论以及最新的TPXO6海潮模型和中国近海潮汐资料计算了海潮负荷对佘山台倾斜固体潮的影响,采用BAYTAP-G调和分析软件对佘山台倾斜固体潮观测进行了处理,获得不同潮波的潮汐参数。在此基础上进行海潮负荷改正。负荷改正后,东西分量的振幅因子和相位滞后与理论值较为接近,而南北分量的半日波振幅因子与理论值仍有较大的偏离。结果说明,佘山台倾斜东西分量主要受海潮负荷的影响,超过60%,甚至达到96%(O1);而南北分量受到的非潮汐的影响要比东西分量受到的影响大,如N2波甚至高达70%,但是这也可能是和海潮模型在近海的不精确有关。 相似文献
17.
本文利用中山站弹簧重力仪记录的重力潮汐时间序列、验潮站数据、CATS2008区域和Eot11a全球海潮模型研究重力和海洋潮汐特征。结果表明,在周日频段,潮波O1的海潮振幅达到28 cm,4个主要潮波（Q1、O1、P1和K1）的全球模型与验潮站潮高差之和为4.2 cm,区域模型与验潮站潮高差之和为4.4 cm;在半日频段,潮波M2的海潮振幅达到20 cm,4个主要潮波（N2、M2、S2和K2）的潮高差之和分别为7.7 cm和5.1 cm,说明利用区域模型修正全球模型的重要性。经区域模型修正的全球海潮负荷改正后,重力主波K1、M2和S2的最终残差振幅分别下降了9.84%、56.14%和37.08%,说明区域海潮模型更能反映海洋潮汐的真实特征,用区域模型修正全球海潮模型的有效性得到验证。 相似文献
18.
A tide model (named DN1.0), which contains 12 principal constituents over China seas and the Northwest Pacific is estimated by along-track harmonic analysis with TOPEX/Poseidon altimetry data taken from 1993 to 2002. CSR3.0, FES95.2 and DN1.0 are used respectively to detide the data for the time series of sea level anomaly (SLA) in the Yellow Sea, East China Sea, South China Sea and Northwest Pacific. The SLA curves and the power spectral density show that the major components that exist in SLA in China seas arise from the error of the tide models. 相似文献
19.
XU Jun BAO Jingyang LIU Yanchun YU Caixia 《地球空间信息科学学报》2007,10(2):100-104
A tide model (named DN1.0), which contains 12 principal constituents over China seas and the Northwest Pacific is estimated by along-track harmonic analysis with TOPEX/Poseidon altimetry data taken from 1993 to 2002. CSR3.0, FES95.2 and DN1.0 are used respectively to detide the data for the time series of sea level anomaly (SLA) in the Yellow Sea, East China Sea, South China Sea and Northwest Pacific. The SLA curves and the power spectral density show that the major components that exist in SLA in China seas arise from the error of the tide models. 相似文献
20.
The impact of the dynamic sea surface topography on the quasi-geoid in shallow coastal waters 总被引：1，自引：1，他引：0
In this study, we examine the impact of instantaneous dynamic sea surface topography (DT) corrections to be applied to altimeter-derived sea surface slopes on the quasi-geoid in the shallow and coastal waters of the North Sea. In particular, we investigate the added value of DT corrections obtained from a shallow-water hydrodynamic model. These corrections comprise the contributions of ocean tides, wind- and pressure-driven (surge), and density-driven (baroclinic) water-level variations including the interactions between them. As a reference, we used tidal corrections derived from the global ocean tide model GOT4.7, surge corrections derived from the MOG2D model, and corrections for the time-averaged baroclinic contribution computed as differences between the DTU10 mean sea surface model and the EGG08 quasi-geoid. From a spectral analysis, we found that the baroclinic and surge parts of the DT mainly contribute to improvements in the signal-to-noise ratio (SNR) at longer wavelengths down to $100{-}200~\hbox {km}$ and that the improvements increase towards the southern North Sea. We also found that the shallow-water hydrodynamic model provides better tidal corrections compared to the GOT4.7 global ocean tide model, which are most pronounced in the southern North Sea and affect almost the entire spectrum. Very small differences (mostly below ${\pm } 2~\hbox {cm}$ ) are observed between the quasi-geoid solutions obtained using the different sets of DT corrections. We showed that the variance component estimation provides too optimistic variance factors for the shipboard data set relative to the altimeter-derived quasi-geoid slopes. Hence, the limited impact of DT corrections is due to the fact that altimeter-derived quasi-geoid slopes hardly contribute to the estimated quasi-geoid if shipboard gravity data are included. When computing quasi-geoid solutions without shipboard gravity data, we found that less accurate or incomplete DT corrections may cause errors in the quasi-geoid with systematic spatial patterns. These systematic patterns disappear or are reduced significantly when using the DT corrections provided by the shallow-water hydrodynamic model. The main contributor to this improvement is the better tidal correction provided by the shallow-water hydrodynamic model compared to the GOT4.7 global ocean tide model. Seen the improvements of the global ocean tide models over the last two decades, we expect that in the near future global ocean tide models perform as well as dedicated regional models such as DCSM. Critical issue is, however, access to high-quality local bathymetric data. 相似文献