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1.
对ＧＥＯＳＡＴ测高卫星在中国近海区域（０°－３５°Ｎ,１０５°－１２７°Ｅ）以及１２７°－１３５°Ｅ内６个ＥＲＭ周期（１９８７年１月１日－４月１２日）的地球物理数据记录（ＧＤＲ）中的数据进行了编辑和预处理．根据卫星弧段的实际长度选取了混合轨道误差模型,并采用最小二乘技术对上升弧段与下降弧段交叠点处的不符值进行了平差计算．处理结果表明,所选用的方法可以大大地消除径向轨道误差的影响,使交叠点处的不符值由原来的５６ｃｍ（ＲＭＳ）降低到现在的２４ｃｍ（ＲＭＳ）在此基础上,构造出６个１°×１°的中国近海海平面及其平均海平面．该平面被称为＂测高大地水准面＂与美国Ｏｈｉｏ州立大学的ＯＳＵ９１Ａ重力场模型的大地水准面相比,两者具有同等量级的精度及一致的形态。  相似文献   

2.
The mean sea surface height (MSSH) refers to the average of the long-term sea height. The quasi-sea surface topography (QSST) is usually defined as the height difference between the MSSH and the geoid. As to 100 years of time yardstick of geodesy, the time that satellite altimetry data sets spanned is relatively shorter, in this paper, the QSST refers to the residual sea surface height (RSSH) that shows the height dif-ference between MSSH derived from altimetry and the geoid[1]. As w…  相似文献   

3.
近海岸区域平均海面高在大地测量学、物理海洋学以及地球物理学研究中具有非常重要的意义.受各种条件的制约和限制，目前卫星测高技术主要应用于深海区域，在近海区域尤其是海岸线附近区域的应用几乎为空白.本文根据ERS-1测高卫星回波波形特征，采用五参数线性模型，由最小二乘拟合方法，对近海区域尤其是靠近海岸线附近的ERS-1测高波形数据进行波形重构.比较波形重构前、后解算平均海面高，表明波形重构技术不仅明显改善了解算近海海面高的精度，而且增加了近海测高海平面的分辨率，并使卫星测高有效观测延伸至海岸线附近.随后，本文利用波形重构后海面高数据构造了近海多年平均海平面，并对我国近海海平面特征进行了初步分析.  相似文献   

4.
The transformation from the gravimetric to the GPS/levelling-derived geoid using additional gravity information for the covariance function of geoid height differences has been investigated in a test area in south-western Canada. A “corrector surface” model, which accounts for datum inconsistencies, long-wavelength geoid errors, vertical network distortions and GPS errors, has been constructed using least-squares collocation. The local covariance function of geoid height differences is usually obtained from residual values between the GPS/levelling and gravimetric geoid heights after the elimination of all known systematic distortions. If additional gravity data (in the form of gravity anomalies) are available, the covariance function of geoid height differences can be determined by the following steps: (1) transforming the GPS/levelling-derived geoid heights into gravity anomalies; (2) forming differences between the computed in step 1 and given gravity anomalies; (3) determining the parameters of the local covariance function of the gravity anomaly differences; (4) constructing an analytical covariance model for the geoid height differences from the covariance function of the gravity anomaly differences using the parameters derived in step 3. The advantage of the proposed method stems from the great number of gravity data used to derive the empirical covariance function. A comparison with the least-squares adjustment shows that the standard deviation of the residuals of the predicted geoid height differences with respect to the control point values decreases by 2.4 cm.  相似文献   

5.
De Lacy  M.C.  Rodríguez-Caderot  G.  Marín  E.  Ruiz  A.  Borque  M.J.  Gil  A.J.  Biagi  L. 《Studia Geophysica et Geodaetica》2001,45(1):55-66
Two new GPS surveys have been carried out to check the accuracy of an existing gravimetric geoid in a test area located in northern Andalusia (Spain). The fast collocation method and the remove-restore procedure have been used for the computation of the quasigeoid model. The Spanish height system is based on orthometric heights, so the gravimetrically determined quasigeoid has been transformed to a geoid model and then compared to geoid undulations provided by GPS and levelling at benchmarks belonging to the Spanish first-order levelling network. The discrepancies between the gravimetric solution and GPS/levelling undulations amount to ±2 cm for one survey and ±5 cm for another after fitting a plane to the geoid model.  相似文献   

6.
基于卫星测高的海域大地水准面   总被引：7，自引：1，他引：7       下载免费PDF全文
利用测高数据的一次差分计算海域垂线偏差，有效降低了动力海面地形和系统残差对垂线偏差的影响；然后根据扰动场元间的协方差函数是具有各态历经性的平稳随机函数这一特征，提出了利用垂线偏差精确逼近海域大地水准面的协方差函数. 而海域大地水准面的精确确定，为从测高数据中精确分离动力海面地形提供了条件. 本文还利用Topex/Poseidon、ERS 1/2测高数据计算了全球海域大地水准面和动力海面地形，证明了本文所述方法是科学合理的.  相似文献   

7.
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8.
The computation of mean sea surface heights from a set of collinear Geosat ERM altimeter data tracks was carried out in a collinear adjustment, where 1 cy/rev cosine and sine coefficients for each track are estimated, so the differences between the collinear tracks are minimized. Then bias/tilt cross-over adjustments of stacked Geosat and Seasat altimetry were carried out. The problems with the free surface in the cross-over adjusted altimetric surface were treated using the absolute sea surface heights relative to the geoid model OSU89B. In a combined adjustment of the two altimeter data sets using cross-over and height informations simultaneously a RMS of the cross-overs of 0.080 m and a RMS of the sea surface heights relative to OSU89B of 0.611 m were obtained.  相似文献   

9.
Geostrophic surface velocities can be derived from the gradients of the mean dynamic topography—the difference between the mean sea surface and the geoid. Therefore, independently observed mean dynamic topography data are valuable input parameters and constraints for ocean circulation models. For a successful fit to observational dynamic topography data, not only the mean dynamic topography on the particular ocean model grid is required, but also information about its inverse covariance matrix. The calculation of the mean dynamic topography from satellite-based gravity field models and altimetric sea surface height measurements, however, is not straightforward. For this purpose, we previously developed an integrated approach to combining these two different observation groups in a consistent way without using the common filter approaches (Becker et al. in J Geodyn 59(60):99–110, 2012; Becker in Konsistente Kombination von Schwerefeld, Altimetrie und hydrographischen Daten zur Modellierung der dynamischen Ozeantopographie 2012). Within this combination method, the full spectral range of the observations is considered. Further, it allows the direct determination of the normal equations (i.e., the inverse of the error covariance matrix) of the mean dynamic topography on arbitrary grids, which is one of the requirements for ocean data assimilation. In this paper, we report progress through selection and improved processing of altimetric data sets. We focus on the preprocessing steps of along-track altimetry data from Jason-1 and Envisat to obtain a mean sea surface profile. During this procedure, a rigorous variance propagation is accomplished, so that, for the first time, the full covariance matrix of the mean sea surface is available. The combination of the mean profile and a combined GRACE/GOCE gravity field model yields a mean dynamic topography model for the North Atlantic Ocean that is characterized by a defined set of assumptions. We show that including the geodetically derived mean dynamic topography with the full error structure in a 3D stationary inverse ocean model improves modeled oceanographic features over previous estimates.  相似文献   

10.
We present a geoid model for the area of Lake Vostok, Antarctica, from a combination of local airborne gravity, ice-surface and ice-thickness data and a lake bathymetry model. The topography data are used for residual terrain modeling (RTM) in a remove–restore approach together with GOCE satellite data. The quasigeoid is predicted by least-squares collocation (LSC) and subsequently converted to geoid heights. Special aspects of that method in presence of an ice sheet are discussed.It is well known that a body freely floating in water is in a state of hydrostatic equilibrium (HE). This usually applies, e.g., to ice shelves or sea ice. However, it has been shown that this is valid also for the ice sheet covering the subglacial Lake Vostok. Thus, we demonstrate the use of such a refined regional geoid model for glaciological and geophysical applications by means of the HE surface of that lake. The mean quadratic residual geoid signal (0.56 m) w.r.t. the GOCE background model exceeds the residual variations of the estimated apparent lake level (ALL) (0.26 m) within the central part of the lake. An approach considering the actual geopotential at the ALL has been derived and subsequently applied. In this context, downward continuation of the potential field within the ice sheet as well as the latitudinal tilt of off-geoid equipotential surfaces are discussed. In view of the accuracy of the ice-thickness measurements that dominate the total error budget of the estimated ALL these effects are negligible. Thus, the HE surface of subglacial lakes may safely be described by a constant height bias in small-scale regional applications. However, field continuation is significant with respect to the formal uncertainty of the quasigeoid, which is at the level of 5 cm given that accurate airborne gravity data (±2 mGal) are available.  相似文献   

11.
Free-Air Anomalies (FAA) for the Norwegian marine area including some parts of the North Sea, the Norwegian Sea and the Barents Sea are computed from satellite altimetry data. A total of 84 cycles of ERS2 along-track data, 25 cycles of ENVISAT along-track data and high density ERS1 data during its geodetic mission are used. The new geopotential model from the Gravity Recovery and Climate Experiment (GRACE) mission, GGM02S (Tapely et al., 2005) is used to compute the long wavelength contributions of the geoid and the FAA. To correct data for mean dynamic topography, the available Levitus climatology model (Levitus and Boyer, 1994) is used. Corrected data are then used to compute along-track gradients in each cycle-pass to suppress the orbital and the atmospheric errors below the noise level of the altimeter. Resulted gradients are then stacked and the east-west and the north-south components of the deflection of verticals are computed where ascending and descending tracks meet each other. Finally, the inverse Vening-Meinesz formula is implemented on the gridded deflections to compute FAA. Results are then compared with available marine and airborne data. Standard deviations of ± 4.301 and ± 6.159 mGal in comparison with airborne and marine FAA were achieved. Thereafter, the derived anomalies are combined with marine and airborne FAA together with the land FAA to compute a fine resolution geoid for Norway and the surrounding marine areas. This geoid is evaluated over sea and land with the synthetic geoid (the geoid derived from the mean sea surface by subtracting the mean dynamic topography) and Global Positioning System (GPS)-levelling and the standard deviations of the differences are ± 20.9 and ± 12.8 cm respectively. ali.soltanpour@ntnu.no, hossein.nahavandchi@ntnu.no, kourosh.ghazavi@ntnu.no  相似文献   

12.
由于卫星观测技术的发展，现在已能利用测高大地水准面简捷可靠地研究海底构造与动力问题. 根据Geosat T2/ERM、Topex/Poseidon 和ERS 1/2测高数据给定的0°N ～45°N、100°E～150°E范围内4′×4′大地水准面，采用全球地形/均衡的重力位效应改正，计算布格、格莱尼和均衡大地水准面. 由格莱尼大地水准面反演Moho面埋深，再从均衡大地水准面起伏推算小尺度地幔流应力场. 结果表明，菲律宾海和南海显示了与磁条带、扩张脊对应或斜交的高频成分大地水准面起伏条带. 各边缘海盆的Moho面埋深有往南变浅的趋势，与菲律宾海各海盆的Moho面埋深大致相当，说明琉球—台湾—菲律宾岛弧两侧的构造动力强度基本相近. 从各种构造特征和大、中、小尺度的地幔流应力场的驱动机制，可以证明岛弧内侧的边缘海具有不同于大洋、大陆的独特构造动力格局和特征.  相似文献   

13.
This paper deals with the analysis of gravity anomaly and precise levelling in conjunction with GPS-Levelling data for the computation of a gravimetric geoid and an estimate of the height system bias parameter No for the vertical datum in Pakistan by means of least squares collocation technique. The long term objective is to obtain a regional geoid (or quasi-geoid) modeling using a combination of local data with a high degree and order Earth gravity model (EGM) and to determine a bias (if there is one) with respect to a global mean sea surface. An application of collocation with the optimal covariance parameters has facilitated to achieve gravimetric height anomalies in a global geocentric datum. Residual terrain modeling (RTM) technique has been used in combination with the EGM96 for the reduction and smoothing of the gravity data. A value for the bias parameter No has been estimated with reference to the local GPS-Levelling datum that appears to be 0.705 m with 0.07 m mean square error. The gravimetric height anomalies were compared with height anomalies obtained from GPS-Levelling stations using least square collocation with and without bias adjustment. The bias adjustment minimizes the difference between the gravimetric height anomalies with respect to residual GPS-Levelling data and the standard deviation of the differences drops from 35 cm to 2.6 cm. The results of this study suggest that No adjustment may be a good alternative for the fitting of the final gravimetric geoid as is generally done when using FFT methods.  相似文献   

14.
Estimation of ocean circulation is investigated via assimilation of satellite measurements of the dynamic ocean topography (DOT) into the global finite-element ocean model (FEOM). The DOT was obtained by means of a geodetic approach from carefully cross-calibrated multi-mission altimeter data and GRACE gravity fields. The spectral consistency was achieved by consistently filtering both, the sea surface and the geoid. The filter length is determined by the spatial resolution of the gravity field and corresponds to approximately 241 km half width for the GRACE-based gravity field model ITG-Grace03s.The assimilation of the geodetic DOT was performed by employing a local singular evolutive interpolated Kalman (SEIK) filter in combination with the method of weighting of observations. It is shown that this approach leads to a successful assimilation technique that reduced the RMS difference between the model and the data from 16 cm to 5 cm during one year of assimilation. The ocean model returns an optimized mean dynamic ocean topography. The effects of assimilation on transport estimates across several hydrographic World Ocean Circulation Experiment (WOCE) sections show improvements compared to the FEOM run without data assimilation. As a result of the assimilation, DOT estimates are available in the polar or coastal regions where the geodetic estimates from satellite data alone are not adequate. Furthermore, more realistic features of the ocean can be seen in these areas compared to those obtained using the filtered data fields.  相似文献   

15.
A unified global height reference system as a basis for IGGOS   总被引：1，自引：0，他引：1  
The definition of a global height reference system is based on a mean sea surface, gravity field parameters, and a three-dimensional terrestrial reference frame (TRF). Tide gauge records, satellite altimetry, gravity measurements on Earth and from space, TRF coordinates, and spirit levelling have to be combined for the realization of the vertical reference frame. Observations and parameters have to be consistent with respect to the used standards, conventions and models. They have to provide globally unified reference surfaces (geoid or quasigeoid, respectively, and mean sea surface). The continental reference systems of Europe (EUREF, ECGN) and South America (SIRGAS) are considering these requirements in their strategies. They are presented here, and slightly different definitions and realizations for a globally unified height reference system are discussed.  相似文献   

16.
On the basis of the GRIM4-S1 satellite-only Earth gravity model, being accomplished in a common effort by DGFI and GRGS, a combination solution, called GRIM4-C1, has been derivcd using 1° × 1° mean gravity anomalies and 1° × 1° Seasat altimeter derived mean geoid undulations. In the meantime improvements could be achieved by incorporating more tracking data (GEOSAT, SPOT2-DORIS) into the solution, resulting in the two new parallel versions, the satellite-only gravity model GRIM4-S2 and the combined solution GRIM4-C2p (preliminary). All GRIM4 Earth gravity models cover the spectral gravitational constituents complete up to degree and order 50.In this report the emphasis is on the discussion of the combined gravity models: combination and estimation techniques, capabilities for application in precise satellite orbit computation and accuracies in long wavelength geoid representation. It is shown that with the new generation of global gravity models general purpose satellite-only models are no longer inferior to combination solutions if applied to satellite orbit restitution.  相似文献   

17.
The microwave radiation of the sea surface, which is denoted by the sea surface brightness temperature, is not only related with sea surface salinity (SSS) and temperature (SST), but also influenced by sea surface wind. The errors of wind detected by satellite sensor have significant influences on the accuracy of SSS and SST retrieval. The effects of sea surface wind on sea surface brightness temperature, i.e. △Th,v, and the relations among △Th,v, wind speed, sea surface tempera- ture, sea surface salinity and incidence angle of observation are investigated. Based on the investi- gations, a new algorithm depending on the design of a single radiometer with double polarizations and multi-incidence angles is proposed. The algorithm excludes the influence of sea surface wind on SSS and SST retrieval, and provides a new method for remote sensing of SSS and SST.  相似文献   

18.
Temporal variations in the nine elements of the Earth's inertia ellipsoid due to sea surface topography dynamics were derived from TOPEX/POSEIDON altimeter data 1993 - 1996. The variations amount to about 10 mm in the position of the center of the Earth's inertia ellipsoid (E i ), 0.15' in the polar axis direction of E i and to about 0.0003 in the denominator of its polar flattening. The approach used is based on the temporal variations of distortions computed by means of the geopotential model EGM96 which is used as reference.  相似文献   

19.
基于有限元方法的陆海大地水准面衔接   总被引：1，自引：1，他引：0       下载免费PDF全文
大陆上用重力数据和GPS水准数据确定(似)大地水准面,海洋上用卫星测高数据确定(似)大地水准面.由于沿海地区和近岸海域往往缺少完好的重力数据,近岸海域卫星测高数据质量相对较差,两类大地水准面在陆海相接区域精度偏低且存在拼合差.纯几何方法拟合陆海局部区域大地水准面,不能顾及大地水准面的物理特性,拟合结果不稳定.顾及到大地水准面的物理特性,依据其在局部所应满足的数学物理方程,拟合陆海局部区域大地水准面问题,转化为Laplace第一边值问题.讨论了有限元法衔接陆海局部区域大地水准面的数学思想,给出了相应的数学模型.  相似文献   

20.
The study on the South China Sea (SCS) circulation has a history of more than 40 years. Nevertheless, the SCS circulation is not fully understood compared with the Bohai Sea, Yellow Sea and East China Sea (ECS). Many numerical studies on the SCS circulati…  相似文献   

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