共查询到16条相似文献，搜索用时 171 毫秒
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地形改正与地形直接影响的转化关系 总被引：1，自引：0，他引：1
传统的第三边值问题的解算方法有Molodensky算法和Stokes-Helmert算法两种。在Molodensky算法中使用的地形改正和Stokes-Helmert算法中使用的直接影响均由大地水准面外地形产生,因而必然存在关系。本文通过推导给出了直接影响是地形改正、层间改正与压缩地形影响3项之和的结论。在此基础上,给出了直接影响的质量线平面积分算法、质量棱柱平面积分算法和地形改正的球面积分算法。此外本文还推导了布格球冠层间改正算法。通过实验得出,直接影响的质量线平面积分算法和质量棱柱平面积分算法与传统球面积分算法的差异分别为3.81和1.64 m Gal;地形改正球面积分算法与传统质量线、质量棱柱平面积分的差异分别为3.92和1.69 m Gal。该结果说明,本文推导的直接影响与地形改正的关系式是正确有效且实用的。 相似文献
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在重力归算中,局部地形改正在重力勘探、地壳结构分析和大地水准面计算等领域有着重要意义,但严格棱柱体积分公式计算效率低,而快速计算公式则会降低计算精度。本文利用CUDA并行编程平台,提出一种地形格网重新编码和严格棱柱体积分八分量拆解方法,实现了基于CPU+GPU异构并行技术的严格棱柱体积分计算地形改正快速并行算法,克服了GPU各个线程计算任务分配和线程计算超载问题,解决了局部地形改正的高分辨率、高精度严密公式的快速计算难题。通过试验,在显卡型号为Tesla V100的计算机上进行4°×6°范围,积分半径40'和分辨率1'的局部地形改正计算仅需1.5 s;分辨率10″的局部地形改正计算仅需14.6 min;进行分辨率3″的地形改正计算耗时45.7 h,而传统串行算法则难以完成计算。在保证微伽级以上计算精度的条件下,计算加速比最高达到850倍以上,有效缩短了计算耗时,提高了计算效率。本文还依据上述并行算法对全国范围地形改正量进行计算。结果表明,我国地形改正量普遍低于80 mGal（1 Gal=10-2 m/s2）,平均值1.83 mGal,最大值达到196 mGal。 相似文献
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李炎寅 《测绘与空间地理信息》2017,(12):213-215
为了提高接收机码间偏差的计算效率和精度,利用CODE中心发布的全球VTEC地图和卫星码间偏差,通过内"预测-校正"法快速解算接收机码间偏差,并结合VTEC多项式对内插结果进行误差项改正。新算法解算的码间偏差与IGS发布的数据差值基本维持在0.2 ns以内,表明该算法计算精度较高,且效率明显高于传统方法。 相似文献
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全国高分辨率格网地形和均衡改正的确定 总被引：16，自引：0，他引：16
在分析现有多种方法计算地形及均衡改正特点的基础上 ,在国内首次提出采用组合法确定格网地形及均衡改正的方案 ,并编制一套实用化的计算软件 ,且应用该软件确定全国 30″× 30″格网地形与均衡改正。通过采用严格积分法 (四棱柱体法 )检验 ,证明地形改正的计算误差最大不会超过 1mGal( 1Gal=1cm/s2 ) ,均衡改正的计算误差最大不会超过 2mGal,是目前确定地形及均衡改正分辨率高、计算精度好、速度快的方法 ,值得在相关领域广泛推广与使用 相似文献
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本文分析了空间重力异常精度对水准测量高差重力异常改正的影响。在江苏两处试验区分别采用实测重力和布格异常数据库两种改正方法,计算测段重力异常改正值,对比两者间的差异。结果表明：未顾及地形起伏的实测重力点分布是导致两种改正方法改正值差异大的主要因素;地形起伏较大区域,水准线路出现转折或倾斜过大时,需加测重力,采用实测重力进行水准测量高差重力异常改正;平坦小区域内,利用布格异常数据库与实测重力进行水准测量高差重力异常改正的精度相当。 相似文献
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联合使用位模型和地形信息的陆区航空重力向下延拓方法 总被引：1，自引：0，他引：1
为了规避传统逆Poisson积分向下延拓解算过程的不适定性问题,借鉴导航定位中的"差分"概念,利用超高阶位模型直接计算海域航空重力测量向下延拓改正数的方法。本文在此基础上提出联合使用重力位模型和地形高数据,计算陆部航空重力向下延拓总改正数的改进方案,以飞行高度面与地面对应点的位模型差分信息表征总改正数的中长波分量,以相对应的局部地形改正差分修正量表征总改正数的中高频成分,从而实现航空重力数据点对点向地面的全频段延拓。在地形变化不同区域,联合使用EGM2008位模型、地面实测重力和高分辨率高程数据进行了实际数值计算和精度评估,验证了该方法的有效性。 相似文献
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概括了空间重力异常和布格重力异常的计算方法,计算了中安第斯山局部地区的空间重力异常、地形改正和布格重力异常,发现了其在海拔较高地区多为负值。 相似文献
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Anestis J. Romaides Christopher Jekeli Donald H. Eckhardt Charles L. Taylor 《Journal of Geodesy》1991,65(4):230-242
An experiment was conducted in 1987 in search for a possible non-Newtonian component to gravity. The test compared accurately measured gravity values on a 600 m tower with upward continued surface gravity. The results indicated a dominant attractive non-Newtonian force that asymptotically approached -540 µGal at the top of the tower. An exhaustive search of possible error sources led to the discovery that our surface data did not accurately represent some of the local topographic features. The surface survey was supplemented by gravity data to remove some of the biases that were caused by the misrepresentation. In addition, a rigorous terrain correction was applied to the surface data resulting in terrain-corrected Bouguer anomalies. These anomalies were then upward continued using two independent techniques. The terrain effect was added back to the predicted values at altitude. With this procedure almost the entire non-Newtonian effect was explained. Currently we find no conclusive evidence for a non-Newtonian force over the range of several hundred meters. 相似文献
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Any errors in digital elevation models (DEMs) will introduce errors directly in gravity anomalies and geoid models when used
in interpolating Bouguer gravity anomalies. Errors are also propagated into the geoid model by the topographic and downward
continuation (DWC) corrections in the application of Stokes’s formula. The effects of these errors are assessed by the evaluation
of the absolute accuracy of nine independent DEMs for the Iran region. It is shown that the improvement in using the high-resolution
Shuttle Radar Topography Mission (SRTM) data versus previously available DEMs in gridding of gravity anomalies, terrain corrections
and DWC effects for the geoid model are significant. Based on the Iranian GPS/levelling network data, we estimate the absolute
vertical accuracy of the SRTM in Iran to be 6.5 m, which is much better than the estimated global accuracy of the SRTM (say
16 m). Hence, this DEM has a comparable accuracy to a current photogrammetric high-resolution DEM of Iran under development.
We also found very large differences between the GLOBE and SRTM models on the range of −750 to 550 m. This difference causes
an error in the range of −160 to 140 mGal in interpolating surface gravity anomalies and −60 to 60 mGal in simple Bouguer
anomaly correction terms. In the view of geoid heights, we found large differences between the use of GLOBE and SRTM DEMs,
in the range of −1.1 to 1 m for the study area. The terrain correction of the geoid model at selected GPS/levelling points
only differs by 3 cm for these two DEMs. 相似文献
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Geoid, topography, and the Bouguer plate or shell 总被引：1，自引：1，他引：1
Topography plays an important role in solving many geodetic and geophysical problems. In the evaluation of a topographical
effect, a planar model, a spherical model or an even more sophisticated model can be used. In most applications, the planar
model is considered appropriate: recall the evaluation of gravity reductions of the free-air, Poincaré–Prey or Bouguer kind.
For some applications, such as the evaluation of topographical effects in gravimetric geoid computations, it is preferable
or even necessary to use at least the spherical model of topography. In modelling the topographical effect, the bulk of the
effect comes from the Bouguer plate, in the case of the planar model, or from the Bouguer shell, in the case of the spherical
model. The difference between the effects of the Bouguer plate and the Bouguer shell is studied, while the effect of the rest
of topography, the terrain, is discussed elsewhere. It is argued that the classical Bouguer plate gravity reduction should
be considered as a mathematical construction with unclear physical meaning. It is shown that if the reduction is understood
to be reducing observed gravity onto the geoid through the Bouguer plate/shell then both models give practically identical
answers, as associated with Poincaré's and Prey's work. It is shown why only the spherical model should be used in the evaluation
of topographical effects in the Stokes–Helmert solution of Stokes' boundary-value problem. The reason for this is that the
Bouguer plate model does not allow for a physically acceptable condensation scheme for the topography.
Received: 24 December 1999 / Accepted: 11 December 2000 相似文献
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Lars E. Sjöberg 《Journal of Geodesy》2009,83(10):967-972
The topographic bias is defined as the error/bias committed by continuing the external gravity field inside the topographic
masses by a harmonic function. We study the topographic bias given by a digital terrain model defined by a spherical template,
and we show that the topographic bias is given only by the potential of an inner-zone cap, and it equals the bias of the Bouguer
shell, independent of the size of the cap. Then we study the effect on the real Earth by decomposing its topography into a
template, and we show also in this case that the topographic bias is that of the Bouguer shell, independent of the shape of
the terrain. Finally, we show that the topographic potential of the terrain at the geoid can be determined to any precision
by a Taylor expansion outside the Earth’s surface. The last statement is demonstrated by a Taylor expansion to fourth order. 相似文献
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Four different implementations of Stokes' formula are employed for the estimation of geoid heights over Sweden: the Vincent
and Marsh (1974) model with the high-degree reference gravity field but no kernel modifications; modified Wong and Gore (1969)
and Molodenskii et al. (1962) models, which use a high-degree reference gravity field and modification of Stokes' kernel;
and a least-squares (LS) spectral weighting proposed by Sj?berg (1991). Classical topographic correction formulae are improved
to consider long-wavelength contributions. The effect of a Bouguer shell is also included in the formulae, which is neglected
in classical formulae due to planar approximation. The gravimetric geoid is compared with global positioning system (GPS)-levelling-derived
geoid heights at 23 Swedish Permanent GPS Network SWEPOS stations distributed over Sweden. The LS method is in best agreement,
with a 10.1-cm mean and ±5.5-cm standard deviation in the differences between gravimetric and GPS geoid heights. The gravimetric
geoid was also fitted to the GPS-levelling-derived geoid using a four-parameter transformation model. The results after fitting
also show the best consistency for the LS method, with the standard deviation of differences reduced to ±1.1 cm. For comparison,
the NKG96 geoid yields a 17-cm mean and ±8-cm standard deviation of agreement with the same SWEPOS stations. After four-parameter
fitting to the GPS stations, the standard deviation reduces to ±6.1 cm for the NKG96 geoid. It is concluded that the new corrections
in this study improve the accuracy of the geoid. The final geoid heights range from 17.22 to 43.62 m with a mean value of
29.01 m. The standard errors of the computed geoid heights, through a simple error propagation of standard errors of mean
anomalies, are also computed. They range from ±7.02 to ±13.05 cm. The global root-mean-square error of the LS model is the
other estimation of the accuracy of the final geoid, and is computed to be ±28.6 cm.
Received: 15 September 1999 / Accepted: 6 November 2000 相似文献