共查询到18条相似文献，搜索用时 532 毫秒
1.
利用调和常数内插的局域无缝深度基准面构建方法 总被引：1，自引：0，他引：1
为实现局域水域垂直基准间的无缝转换,从深度基准面计算原理出发,根据潮波传播特征,提出了一种基于潮汐调和常数内插的无缝深度基准面建立方法,该方法较传统常用方法具有更高的精度和稳定性。通过长江口区域的实验验证了该方法的正确性及可行性,并在该区域建立了无缝深度基准面模型。 相似文献
2.
《武汉大学学报(信息科学版)》2016,(1)
分析了不同海洋垂直基准面的含义及相互转换关系,研究了在高程基准和地球椭球面上表示深度基准面的实现途径,利用长期验潮站观测数据验证了不同时段平均水位和深度基准的确定精度水平。以南海为例,构建了深度基准面(L值)模型、正常高模型和大地高模型。分析和验证表明,长期验潮站的垂直基准可以实现cm级精度确定。更新和统一验潮站垂直基准确定,为海域垂直基准及转换模型提供了必要的基础条件。 相似文献
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为实现远岸潮汐精确监测及潮位海图高程转换,基于GPS事后动态处理技术(PPK)开展了远距离高精度潮位观测、提取及垂直基准面确定和转换模型构建方法研究。分别探讨了在锚定和走航情况下瞬时水面高程信号改正方法及潮位有效信息提取的最优截止频率,并给出了在不同情况下深度基准面大地高的计算方法模型及区域无缝深度基准面大地高构建模型。在实际试验中,基线距离在100km范围内,获得了基于深度基准的GPS潮位,精度优于10cm。 相似文献
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根据长江口水域长期验潮站的潮位资料进行大量深度基准面传递试验,研究了深度基准面传递精度与潮汐类型值差、传递距离、地形环境特征之间的具体数值关系。该研究成果对长江口水域里深度基准面传递精度指标估计具有参考意义。 相似文献
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随着全球导航卫星系统(GNSS)的完善,以及海洋工程的日趋增多,对于区域海洋无缝垂直基准建模及其转换精度的要求也不断提高。本文针对建立我国区域海洋无缝垂直基准体系的现状进行探讨,概要性地介绍了有关模型的建立和海洋垂直基准间的转换方法,并配案例,为相关领域的研究者提供了技术参考。 相似文献
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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
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
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无缝仿射基准转换模型的方差分量估计 总被引：1，自引：1，他引：0
以无缝仿射基准变换为例,研究了无缝基准转换模型的方差分量估计理论,导出无缝基准变换过程中两套坐标的方差分量估计公式。通过模拟试验分析表明,采用方差分量估计方法能正确地恢复出客观体现两套坐标误差的方差值,从而有效提高无缝基准转换精度。 相似文献
11.
We present a combined approach for the realization of the (quasi-)geoid as a height reference surface and the vertical reference surface at sea (chart datum). This approach, specifically designed for shallow seas and coastal waters, provides the relation between the two vertical reference surfaces without gaps down to the coast. It uses a regional hydrodynamic model, which, after vertical referencing, provides water levels relative to a given (quasi-)geoid. Conversely, the hydrodynamic model is also used to realize a (quasi-)geoid by providing corrections to the dynamic sea surface topography, which are used to reduce radar altimeter-derived sea surface heights to the (quasi-)geoid. The coupled problem of vertically referencing the hydrodynamic model and computing the (quasi-)geoid is solved iteratively. After convergence of the iteration process, the vertically referenced hydrodynamic model is used to realize the chart datum. In this way, consistency between the chart datum and (quasi-)geoid is ensured. We demonstrate the feasibility and performance of this approach for the Dutch mainland and North Sea. We show that in the Dutch part of the North Sea, the differences between modeled and observed instantaneous and mean dynamic sea surface topography is 8–10 and 5.8 cm, respectively. On land, we show that the methodology provides a quasi-geoid which has a lower standard deviation (SD) than the European Gravimetric Geoid 2008 (EGG08) and the official Netherlands quasi-geoid NLGEO2004-grav when compared to GPS-levelling data. The root mean square at 81 GPS-levelling points is below 1.4 cm; no correction surface is needed. Finally, we show that the chart datum (lowest astronomical tide, LAT) agrees with the observed chart datum at 92 onshore tide gauges to within 21.5 cm (SD). 相似文献
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受海底地形、开边界驱动水位及底摩擦系数等边界条件的共同影响,当前中国沿岸和近海潮汐场模拟的精度仍显不足。利用精度和分辨率较海图高一级别的水深数据、包含长周期天文气象分潮Sa的由12个主分潮组成的开边界驱动水位及顾及水深空间变化的底摩擦系数等经优化的边界条件,运行二维潮汐数值模式2D-MIKE21,开展黄海海州湾潮汐场模拟。结果表明,天文潮模拟值与海州湾周边6个验潮站1年潮汐表相比,12个主分潮综合预报误差为5.52 cm;与中国海域现有潮汐模型CST1中24个随机点位相比,12个主分潮综合预报误差为7.10 cm。天文潮模拟值和CST1预报值二者与海州湾周边2个验潮站近1个月实测值相比,前者中误差要小于后者。这为在沿岸及近海开展面向海洋测绘应用的潮汐场模拟提供了新思路,同时也表明通过数值模拟的方式构建天文气象分潮Sa是可行的。 相似文献
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M. S. Filmer C. W. Hughes P. L. Woodworth W. E. Featherstone R. J. Bingham 《Journal of Geodesy》2018,92(12):1413-1437
The direct method of vertical datum unification requires estimates of the ocean’s mean dynamic topography (MDT) at tide gauges, which can be sourced from either geodetic or oceanographic approaches. To assess the suitability of different types of MDT for this purpose, we evaluate 13 physics-based numerical ocean models and six MDTs computed from observed geodetic and/or ocean data at 32 tide gauges around the Australian coast. We focus on the viability of numerical ocean models for vertical datum unification, classifying the 13 ocean models used as either independent (do not contain assimilated geodetic data) or non-independent (do contain assimilated geodetic data). We find that the independent and non-independent ocean models deliver similar results. Maximum differences among ocean models and geodetic MDTs reach >150 mm at several Australian tide gauges and are considered anomalous at the 99% confidence level. These differences appear to be of geodetic origin, but without additional independent information, or formal error estimates for each model, some of these errors remain inseparable. Our results imply that some ocean models have standard deviations of differences with other MDTs (using geodetic and/or ocean observations) at Australian tide gauges, and with levelling between some Australian tide gauges, of \({\sim }\pm 50\,\hbox {mm}\). This indicates that they should be considered as an alternative to geodetic MDTs for the direct unification of vertical datums. They can also be used as diagnostics for errors in geodetic MDT in coastal zones, but the inseparability problem remains, where the error cannot be discriminated between the geoid model or altimeter-derived mean sea surface. 相似文献
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Richard H. Rapp 《Journal of Geodesy》1994,69(1):26-31
This paper discusses the separation between the reference surface of several vertical datums and the geoid. The data used includes a set of Doppler positioned stations, transformation parameters to convert the Doppler positions to ITRF90, and a potential coefficient model composed of the JGM-2 (NASA model) from degree 2 to 70 plus the OSU91A model from degree 71 to 360. The basic method of analysis is the comparison of a geometric geoid undulation derived from an ellipsoidal height and an orthometric height with the undulation computed from the potential coefficient model The mean difference can imply a bias of the datum reference surface with respect to the geoid. Vertical datums in the following countries were considered: England, Germany, United States, and Australia. The following numbers represent the bias values of each datum after adopting an equatorial radius of 6378136.3m: England (-87 cm), Germany (4 cm), United States (NGVD29 (-26 cm)), NAVD88 (-72 cm), Australia AHD (mainland, -68 cm); AHD (Tasmania, -98 cm). A negative sign indicates the datum reference surface is below the geoid. The 91 cm difference between the datums in England and Germany has been independently estimated as 80 cm. The 30 cm difference between AHD (mainland) and AHD (Tasmania) has been independently estimated as 40 cm. These bias values have been estimated from data where the geometric/ gravimetric geoid undulation difference standard deviation, at one station, is typically ±100 cm, although the mean difference is determined more accurately.The results of this paper can be improved and expanded with more accurate geocentric station positions, more accurate and consistent heights with respect to the local vertical datum, and a more accurate gravity field for the Earth. The ideas developed here provide insight on the determination of a world height system. 相似文献
15.
海洋重力似大地水准面与区域测高似大地水准面的拟合问题 总被引：3，自引：0，他引：3
研究了将陆地重力似大地水准面与GPS水；住似大地水准面拟合的处理方法推广到海洋的问题．首先从理论上证明了当存在海面地形．则海洋大地水准面与似大地水准面不重合．导出了在海洋上大地水；住面差距与高程异常之间差值的公式．由此给出了求定平均海面相对于区域高程基准的正常高以及测高似大地水准面的计算公式。由于测高平均海面与GPS大地高有相近的精度．提出了将海洋重力似大地水准面与区域测高似大地水准面拟合的处理方法．并利用当前最新的海面地形模型和测高平均海面模型做了数值估计。 相似文献
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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
18.
A 2×2 arc-minute resolution geoid model, CARIB97, has been computed covering the Caribbean Sea. The geoid undulations refer
to the GRS-80 ellipsoid, centered at the ITRF94 (1996.0) origin. The geoid level is defined by adopting the gravity potential
on the geoid as W
0=62 636 856.88 m2/s2 and a gravity-mass constant of GM=3.986 004 418×1014 m3/s2. The geoid model was computed by applying high-frequency corrections to the Earth Gravity Model 1996 global geopotential
model in a remove-compute-restore procedure. The permanent tide system of CARIB97 is non-tidal. Comparison of CARIB97 geoid
heights to 31 GPS/tidal (ITRF94/local) benchmarks shows an average offset (h–H–N) of 51 cm, with an Root Mean Square (RMS) of 62 cm about the average. This represents an improvement over the use of a global
geoid model for the region. However, because the measured orthometric heights (H) refer to many differing tidal datums, these comparisons are biased by localized permanent ocean dynamic topography (PODT).
Therefore, we interpret the 51 cm as partially an estimate of the average PODT in the vicinity of the 31 island benchmarks.
On an island-by-island basis, CARIB97 now offers the ability to analyze local datum problems which were previously unrecognized
due to a lack of high-resolution geoid information in the area.
Received: 2 January 1998 / Accepted: 18 August 1998 相似文献