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101.
Nowadays, Global Geopotential Models (GGMs) are used as a routine stage in the procedures to compute a gravimetric geoid.
The GGMs based geoidal height also can be used for GPS/levelling and navigation purposes in developing countries which do
not have accurate gravimetric geoid models. Also, the GGM based gravity anomaly including the digital elevation model can
be used in evaluation and outlier detections schemes of the ground gravity anomaly data. Further, the deflection of vertical
and gravity gradients components from the GGMs can be used for different geodetic and geophysical interpretation purposes.
However, still a complete and user-friendly software package is not available for universities and geosciences communities.
In this article, first we review the procedure for determination of the basic gravity field and gradient components from the
GGMs, then general MATLAB based software is presented and applied as a sample case study for determination of gravity components
based on the most recent EIGEN-GL04C GRACE model in Sweden.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
102.
Bathymetry data from Sognefjord, Norway, have been included in a terrain model, and their influence on the geoid has been
calculated. The test area, located in the western part of Norway, was chosen due to its deep fjords and high mountains. Inclusion
of bathymetry data in the terrain model altered the computed gravimetric geoid by as much as a few decimeters. The effect
was detectable to a distance of more than 100 km. All calculated geoids, both with and without bathymetry data in the terrain
model, fit the geoidal heights determined by available Global Positioning System (GPS) and levelling heights at the sub-decimetre
level. Contrary to expectations, the accuracy in geoid prediction was reduced when using bathymetric data. The geoid changes
were largest over the fjord where no GPS points were located. Different methods on the same area [isostatic and Residual Terrain
Model (RTM)-terrain reductions] showed differences of approximately 1 m. Rigorous distinction between quasigeoid and geoid
was found to be essential in this kind of area.
Received: 12 May 1997 / Accepted 7 May 1998 相似文献
103.
Unification of vertical datums by GPS and gravimetric geoid models with application to Fennoscandia 总被引:3,自引:0,他引:3
The second Baltic Sea Level (BSL) GPS campaign was run for one week in June 1993. Data from 35 tide gauge sites and five
fiducial stations were analysed, for three fiducial stations (Onsala, Mets?hovi and Wettzell) fixed at the ITRF93 system.
On a time-scale of 5 days, precision was several parts in 109 for the horizontal and vertical components. Accuracies were about 1 cm in comparison with the International GPS Geodynamical
Service (IGS) coordinates in three directions. To connect the Swedish and the Finnish height systems, our numerical application
utilises three approaches: a rigorous approach, a bias fit and a three-parameter fit. The results between the Swedish RH70
and the Finnish N 60 systems are estimated to −19.3 ± 6.5, −17 ± 6 and −15 ± 6 cm, respectively, by the three approaches.
The results of the three indirect methods are in an agreement with those of a direct approach from levelling and gravity measurements.
Received: 3 April 1996 / Accepted: 4 August 1997 相似文献
104.
精化山区大地水准面的一种方法--GPS、测距三角高程与地形的组合 总被引:1,自引:0,他引:1
鉴于我国中西部是多山地区,为满足国家统一高程和山区建设的需要,本文提出了用GPS和测距三角高程的方法确定高程异常,再用地形数据推求重力异常垂直梯度,由此可以经济和快速地实现精化大地水准面的目标。这时边远山区任意一点的精度可达30cm。 相似文献
105.
106.
R. Dietmar Müller David T. Sandwell Brian E. Tucholke John G. Sclater Peter R. Shaw 《Marine Geophysical Researches》1991,13(2):105-129
Geoid data from Geosat and subsatellite basement depth profiles of the Kane Fracture Zone in the central North Atlantic were used to examine the correlation between the short-wavelength geoid (=25–100 km) and the uncompensated basement topography. The processing technique we apply allows the stacking of geoid profiles, although each repeat cycle has an unknown long-wavelength bias. We first formed the derivative of individual profiles, stacked up to 22 repeat cycles, and then integrated the average-slope profile to reconstruct the geoid height. The stacked, filtered geoid profiles have a noise level of about 7 mm in geoid height. The subsatellite basement topography was obtained from a recent compilation of structure contours on basement along the entire length of the Kane Fracture Zone. The ratio of geoid height to topography over the Kane Fracture Zone valley decreases from about 20–25 cm km-1 over young ocean crust to 5–0 cm km-1 over ocean crust older than 140 Ma. Both geoid and basement depth of profiles were projected perpendicular to the Kane Fracture Zone, resampled at equal intervals and then cross correlated. The cross correlation shows that the short-wavelength geoid height is well correlated with the basement topography. For 33 of the 37 examined pro-files, the horizontal mismatches are 10 km or less with an average mismatch of about 5 km. This correlation is quite good considering that the average width of the Kane Fracture Zone valley at median depth is 10–15 km. The remaining four profiles either cross the transverse ridge just east of the active Kane transform zone or overlie old crust of the M-anomaly sequence. The mismatch over the transverse ridge probably is related to a crustal density anomaly. The relatively poor correlation of geoid and basement depth in profiles of ocean crust older than 130–140 Ma reflects poor basement-depth control along subsatellite tracks. 相似文献
107.
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
108.
自1973年以来,NASA已发射了三颗与卫星测高有关的卫星,测高标准误差≥±10cm。已求得全球平均海水面高度图标准误差≤±1m。它的短波成分比卫星重力大地水准面的丰富得多。由于引入卫星测高资料,已把地球重力位系数从原来的22×22阶次提高到现在的180×180阶次,估计在卫星测高加密观测地区,可提高到720×720阶次。现在,卫星测高已成为综合应用卫星SEASAT的主要观测项目之一,这对于研究海洋地球物理和全球性地球动力学问题无疑是一种十分有用的资料。 相似文献
109.
正在进行和即将进行的大量GPS+Levelling测量使得大地水准面也成为直接观测量,因此经典的Molodensky天文重力准已经不能适应这一情况。为了从更广泛的意义上更好地利用各类观测值,本文使用样条函数作为基函数,讨论了局部地区超定边值问题的样条解法。 相似文献
110.
本文利用简捷的球谐分析方法讨论了重力场元在地面和空间的谱分布特征和向下延拓问题,分析了各类测量数据求定重力场的最高分辨率及精度。结果表明,在一个低轨道卫星上以适当的精度(优于10~(-2)E)的重力梯度测量可以获得空间分辨率为100公里、精度高于5mgal和10cm的重力场和大地水准面。 相似文献