21世纪我国面临的测绘基准面问题   总被引：4，自引：0，他引：4  

殷晓冬  田光耀 《测绘工程》2000,9(2):26-31

大地水准面与深度基准面是测绘垂直基准面的主要因素。文中探讨了我国测绘垂直基准面的现状及其存在的问题 ,提出了改进测绘垂直基准面之拙见 ,以便在下一个世纪提到议事日程与同仁商榷。  相似文献   

Sea-level changes, geoid and gravity anomalies due to Pleistocene deglaciation by means of multilayered, analytical Earth models     

G. Di Donato  L. L. A. Vermeersen  R. Sabadini 《Tectonophysics》2000,320(3-4):409-418

A new class of analytical, multilayered, viscoelastic Earth models based on PREM, with an incompressible, linear, viscoelastic Maxwell rheology, is applied to the modeling of global sea-level changes due to Pleistocene deglaciation. Until now, analytical schemes based on normal mode theory, have dealt with at most five layers, an elastic lithosphere, a three layered mantle including a transition zone, and a core (Spada et al., 1992. Geophys. J. Int. 109, 683–700). The novelty of our approach, used for the first time in sea-level studies, stands on an analytical scheme that can reproduce continuous elastic and rheological stratification when a sufficient number of layers is taken into account. We specifically assess the importance of our results for the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite mission. GOCE will resolve the gravity field with a spatial resolution (half-wavelength) of 75 km and amplitude of 1.5 mgal, with a uniform coverage over the Earth, including presently unsurveyed, remote areas. Our models lead to post-glacial rebound induced free air gravity anomalies of a few mgals peak-to-peak in the harmonic degree range l=80–200, which will be discernible by GOCE. This finding demonstrates that post-glacial rebound has a high frequency component in the gravity field that can in principle be resolved by high resolution gravity satellite missions. We show that post-glacial rebound can contribute a substantial fraction to present-day sea-level variations and point out that for the Mediterranean Sea they are of the same order of magnitude as those induced by tectonic processes.  相似文献   

How to handle topography in practical geoid determination: three examples   总被引：3，自引：1，他引：2  

O. C. D. Omang  R. Forsberg 《Journal of Geodesy》2000,74(6):458-466

 Three different methods of handling topography in geoid determination were investigated. The first two methods employ the residual terrain model (RTM) remove–restore technique, yielding the quasigeoid, whereas the third method uses the classical Helmert condensation method, yielding the geoid. All three methods were used with the geopotential model Earth Gravity Model (1996) (EGM96) as a reference, and the results were compared to precise global positioning system (GPS) levelling networks in Scandinavia. An investigation of the Helmert method, focusing on the different types of indirect effects and their effects on the geoid, was also carried out. The three different methods used produce almost identical results at the 5-cm level, when compared to the GPS levelling networks. However, small systematic differences existed. Received: 18 March 1999 / Accepted: 21 March 2000  相似文献   

Effect of the Mean Dynamic Topography on the Geoid-to-Quasigeoid Separation Offshore     

R. Tenzer  I. Foroughi 《Marine Geodesy》2018,41(4):368-381

It is commonly acknowledged that offshore the quasigeoid very closely coincides with the geoid. Nevertheless, the numerical assessment supporting this assumption has not yet been provided. Moreover, the rigorous definition of the quasigeoid surface and consequently the geoid-to-quasigeoid separation offshore is not given in geodetic literature. To address these issues, we define in this study the quasigeoid surface offshore in the context of the mean sea level. We then derive the spectral expressions for computing the geoid-to-quasigeoid separation offshore and apply these expressions estimate the vertical separation between the geoid and the quasigeoid over the world's oceans and marginal seas using the global dataset of the DTU15 mean dynamic topography. By taking the analogy of defining the geoid-to-quasigeoid separation inland by means of the disturbing potential differences of values evaluated on the geoid and at the topographic surface, the computation offshore is practically realized from values of the disturbing potential on the geoid and at the mean sea surface. Our result shows that the geoid-to-quasigeoid separation offshore is completely negligible, with most of the values within the interval ±0.3 mm.  相似文献   

海域航空重力快速构建区域大地水准面     

王晨阳  骆遥  熊盛青  刘诗华  刘祖鉴 《地球物理学报》2021,64(3):907-915

我国在海域开展了大规模的航空重力勘探,这些资料对构建高精度大地水准面具有重要价值.基于此,本文提出一种利用海域航空重力测量数据快速构建大地水准面的方法.该方法基于移去-恢复法思想,利用位场最小曲率方法对航空重力数据进行高精度向下延拓并获取相应的扰动位,实现航空重力测量快速构建海域大地水准面.与斯托克斯积分计算相比,采用了处理效率更高的频率域位场转换,解决了向下延拓及垂向积分时航空重力异常数据空白及扩边问题,具有较高的位场转换精度.本文应用EGM2008模拟航空重力数据进行模型验证,计算结果与其给出的水准面的精度相当;同时,也选取GRAV-D计划的航空重力数据进行实际验证,计算结果与xGEOID18B水准面模型精度基本一致.模型验证和实际应用验证了本方法的实用性.  相似文献   

Transforming ellipsoidal heights and geoid undulations between different geodetic reference frames     

Christopher Kotsakis 《Journal of Geodesy》2008,82(4-5):261-260

Transforming height information that refers to an ellipsoidal Earth reference model, such as the geometric heights determined from GPS measurements or the geoid undulations obtained by a gravimetric geoid solution, from one geodetic reference frame (GRF) to another is an important task whose proper implementation is crucial for many geodetic, surveying and mapping applications. This paper presents the required methodology to deal with the above problem when we are given the Helmert transformation parameters that link the underlying Cartesian coordinate systems to which an Earth reference ellipsoid is attached. The main emphasis is on the effect of GRF spatial scale differences in coordinate transformations involving reference ellipsoids, for the particular case of heights. Since every three-dimensional Cartesian coordinate system ‘gauges’ an attached ellipsoid according to its own accessible scale, there will exist a supplementary contribution from the scale variation between the involved GRFs on the relative size of their attached reference ellipsoids. Neglecting such a scale-induced indirect effect corrupts the values for the curvilinear geodetic coordinates obtained from a similarity transformation model, and meter-level apparent offsets can be introduced in the transformed heights. The paper explains the above issues in detail and presents the necessary mathematical framework for their treatment. An erratum to this article can be found at  相似文献   

大地水准面异常在湖南地区的地球物理解释          下载免费PDF全文

林淼  朱建军  田玉淼  陶肖静 《地球物理学报》2012,55(2):472-483

以湖南地区为例,利用超高阶地球重力位模型EGM2008计算了研究区的重力大地水准面,并采用棱柱体公式和球体公式相结合的方法分别进行了完全地形改正和Airy-Heiskanen局部均衡改正,得到布格大地水准面和均衡大地水准面.对三种大地水准面进行不同波长分量的分离处理,得到包含不同深度异常信息的剩余大地水准面,并结合其他地球物理资料对研究区进行了详细的地球物理解释.结果表明,剩余重力大地水准面可以有效地反映出研究区内的深部构造特征,如深大断裂带分布、构造块体位置、上地幔密度横向分布等,但对地壳内异常结构反映不明显;研究区岩石圈密度变化相对平缓,厚度由东向西增加;根据剩余均衡大地水准面及研究区Airy局部均衡莫霍面,可以大致推测出研究区的莫霍面起伏形态以及均衡状态,可作为一种有用的参考信息.  相似文献   

Gravity,Mean Sea Surface,and Bathymetry Models Comparison in the Canary Islands     

M. J. Sevilla  G. Rodríguez-Velasco 《Marine Geodesy》2013,36(4):313-333

In geodetic and oceanographic studies generally, some reference surfaces are needed. These surfaces must represent as much as possible the gravity field of the Earth and the height/bathymetry systems. In the last years, several gravimetric, bathymetric, and mean sea surface models have appeared. Analyzing them it is possible to see that there are significant discrepancies between the models provided by different authors or organizations; there are also differences between the models and data obtained by independent measurements. We present the analysis of such differences and determine the most representative choice of models, in our opinion, for the Canary Islands region.  相似文献   

On the indirect effect in the Stokes–Helmert method of geoid determination     

L. E. Sjöberg  H. Nahavandchi 《Journal of Geodesy》1999,73(2):87-93

The classical integral formula for determining the indirect effect in connection with the Stokes–Helmert method is related to a planar approximation of the sea level. A strict integral formula, as well as some approximations to it, are derived. It is concluded that the cap- size truncated integral formulas will suffer from the omission of some long-wavelength contributions, of the order of 50 cm in high mountains for the classical formula. This long-wavelength information can be represented by a set of spherical harmonic coefficients of the topography to, say, degree and order 360. Hence, for practical use, a combination of the classical formula and a set of spherical harmonics is recommended. Received: 10 March 1998 / Accepted: 16 November 1998  相似文献   

The continental tectosphere and Earth's long-wavelength gravity field   总被引：2，自引：0，他引：2  

Steven S. Shapiro  Bradford H. Hager  Thomas H. Jordan 《Lithos》1999,48(1-4):135-152

To estimate the average density contrast associated with the continental tectosphere, we separately project the degree 2–36 non-hydrostatic geoid and free-air gravity anomalies onto several tectonic regionalizations. Because both the regionalizations and the geoid have distinctly red spectra, we do not use conventional statistical analysis, which is based on the assumption of white spectra. Rather, we utilize a Monte Carlo approach that incorporates the spectral properties of these fields. These simulations reveal that the undulations of Earth's geoid correlate with surface tectonics no better than they would were it randomly oriented with respect to the surface. However, our simulations indicate that free-air gravity anomalies correlate with surface tectonics better than almost 98% of our trials in which the free-air gravity anomalies were randomly oriented with respect to Earth's surface. The average geoid anomaly and free-air gravity anomaly over platforms and shields are significant at slightly better than the one-standard-deviation level: −11±8 m and −4±3 mgal, respectively. After removing from the geoid estimated contributions associated with (1) a simple model of the continental crust and oceanic lithosphere, (2) the lower mantle, (3) subducted slabs, and (4) remnant glacial isostatic disequilibrium, we estimate a platform and shield signal of −8±4 m. We conclude that there is little contribution of platforms and shields to the gravity field, consistent with their keels having small density contrasts. Using this estimate of the platform and shield signal, and previous estimates of upper-mantle shear-wave travel-time perturbations, we find that the average value of ∂lnρ/∂lnν_s within the 140–440 km depth range is 0.04±0.02. A continental tectosphere with an isopycnic (equal-density) structure (∂lnρ/∂lnν_s=0) enforced by compositional variations is consistent with this result at the 2.0σ level. Without compositional buoyancy, the continental tectosphere would have an average ∂lnρ/∂lnν_s≈0.25, exceeding our estimate by 10σ.  相似文献