联合多种测高数据确定中国边缘海及全球海域的垂线偏差(英文)

On the basis of gravity field model （EIGEN_CG01C）, together with multi-altimeter data, the improved deflection of the vertical gridded in 2＇×2＇ in China marginal sea and gridded in 5＇×5＇ in the global sea was determined by using the weighted method of along-track least squares, and the accuracy is better than 1.2^# in China marginal sea. As for the quality of the deflection of the vertical, it meets the challenge for the gravity field of high resolution and accuracy, it shows that, compared with the shipboard gravimetry in the sea, the accuracy of the gravity anomalies computed with the marine deflection of the vertical by inverse Vening-Meinesz formula is 7.75 m.s ^-2.     

根据多卫星高度计海面高数据推算南中国海及菲律宾海域重力异常(英文)

t Gravity anomalies on a2.5 ×2.5 arc-minute grid in a non-tidal system were derived over the South China and Philippine Seas from multi-satellite altimetry data. North and east components of deflections of the vertical were computed from altimeter-derived sea surface heights at crossover locations, and gridded onto a 2.5 × 2.5 arc-minute resolution grid. EGM96-derived components of deflections of the vertical and gravity anomalies gridded into 2.5 × 2.5 arc-minute resolutions were then used as reference global geopotential model quantities in a remove-restore procedure to implement the Inverse Vening Meinesz formula via the 1D-FFT technique to predict the gravity anomalies over the South China and Philippine Seas from the gridded altimeter-derived components of deflections of the vertical. Statistical comparisons between the altimeter-derived and the shipboard gravity anomalies showed that there is a root-mean-square agreement of 5.7 mgals between them.     

中国西太平洋海域1′×1′垂线偏差模型及精度评估

联合多种测高数据和重力异常数据,设计了观测点距离和测高精度融合的定权方法,采用最小二乘方法和Vening-Meinesz公式,分别构建了西太平洋海域(0°N—40°N,105°E—145°E)1′×1′网格化垂线偏差数字模型。选取两个不同特征区域,将垂线偏差的两个数字模型和EGM2008模型三者进行相互比较分析。结果表明:卯酉分量η的均方根差大于子午分量ξ的均方根差,海底地形复杂的南海特征区域的垂线偏差均方根差大于西太平洋中部的均方根差,构建的两个垂线偏差模型总体均方根差优于1.6″。     

联合多代测高数据建立中国海域重力异常模型

本文联合T/P数据、T/P新轨道数据、ERS数据、GFO数据、GeosatGM数据和ERS-1/168数据,用测高卫星记录点的位置信息直接计算沿轨大地水准面的方向导数,结合测线轨迹方向的方位角在交叉点处推求垂线偏差,然后利用逆Vening-Meinesz公式计算了中国近海(0o～41oN,105o～132oN)2′×2′格网分辨率的海域重力异常模型。将其与CLS_SHOW99重力异常模型比较,统计结果表示与该模型差异的RMS为8.15mgal,在剔除差值大于20mgal的点(剔除3.3%)以后,RMS为4.72mgal;与某海区船测重力异常比较的RMS为8.91mgal。     

ENVISAT测高卫星沿轨大地水准面梯度的海洋垂线偏差法研究

研究了利用沿轨大地水准面梯度数据计算海洋垂线偏差的最小二乘法,首先对ENVISAT测高数据进行各项地球物理改正得到近似测高大地水准面,然后计算沿轨大地水准面的梯度,接着用最小二乘法计算格网垂线偏差东西分量和南北分量的平均值。最后,用该方法计算了南中国海区域及其邻近海域(4°N～25°N,104°E～120°E)的5′×5′垂线偏差南北分量和东西分量,其精度优于7″,并与EGM96模型计算的垂线偏差值进行了比较,证明了该方法的有效性。     

Determination of Geoid over South China Sea and Philippine Sea from Multi-satellite Altimetry Data

A new computational procedure for derivation of marine geoid on a 2.5′×2.5′grid in a non-tidal system over the South China Sea and the Philippine Sea from multi-satellite altimeter sea surface heights is discussed. Single-and dual-satellite crossovers were performed, and components of deflections of the vertical were determined at the crossover positions using Sand-well's computational theory, and gridded onto a 2.5′×2.5′resolution grid by employing the Shepard's interpolation procedure. 2.5′×2.5′grid of EGM96-derived components of deflections of the vertical and geoid heights were then used as reference global geopotential model quantities in a remove-restore procedure to implement the Molodensky-like formula via 1D-FFT technique to predict the geoid heights over the South China Sea and the Philippine Sea from the gridded altimeter-derived components of deflec-tions of the vertical. Statistical comparisons between the altimeter-and the EGM96- derived geoid heights showed that there was a root-mean-square agreement of ±0.35 m between them in a region of less tectonically active geological structures. However, over areas of tectonically active structures such as the Philippine trench, differences of about -19.9 m were obtained.     

Determination of deflections of the vertical using a combination of spherical harmonics and gravimetric data for the area of Greece

The determination of gravimetric deflections of the vertical for the area of Greece is attempted by combining a spherical hamonics model and gravity nomalies using the method of least squares collocation. The components of deflections of the vertical are estimated on a grid with spacing 15′ in latitude and 20′ in longitude covering only the continental area of Greece, where a sufficient number of point gravity anomalies is available. In order to test the accuracy of the determination, gravimetric deflections of the vertical are computed at stations where astrogeodetic data are available. The results show that in a large region of rugged topography and irregular potential field, the prediction is possible with a standard deviation of 18% ... 28% of the root mean square variation of the observations, without taking into account the topography. Furthermore, the estimation of some systematic differences between observed and computed deflections of the vertical is attempted.     

Improving Orthometric Heights Using Precise GPS Measurements

The vertical component obtained from the Global Positioning System (GPS) observations is from the ellipsoid (a mathematical surface), and therefore needs to be converted to the orthometric height, which is from the geoid (represented by the mean sea level). The common practice is to use existing bench marks (around the four corners of a project area and interpolate for the rest of the area), but in many areas bench marks may not be available, in which case an existing geoid undulation is used. Present available global geoid undulation values are not generally as detailed as needed, and in many areas they are not known better than ±1 to ±5 m, because of many limitations. This article explains the difficulties encountered in obtaining precise geoid undulation with some example computations, and proposes a technique of applying corrections to the best available global geoid undulations using detailed free-air gravity anomalies (within a 2° × 2° area) to get relative centimeter accuracy. Several test computations have been performed to decide the optimal block sizes and the effective spherical distances to compute the regional and the local effects of gravity anomalies on geoid undulations by using the Stokes integral. In one test computation a 2° × 2° area was subdivided into smaller surface elements. A difference of 37.34 ± 1.6 cm in geoid undulation was obtained over the same 2° × 2° area when 1° × 1° block sizes were replaced by a combination of 5' × 5' and 1' × 1' subdivision integration elements (block sizes).     

Astronomical-topographic levelling using high-precision astrogeodetic vertical deflections and digital terrain model data

At the beginning of the twenty-first century, a technological change took place in geodetic astronomy by the development of Digital Zenith Camera Systems (DZCS). Such instruments provide vertical deflection data at an angular accuracy level of 0.̋1 and better. Recently, DZCS have been employed for the collection of dense sets of astrogeodetic vertical deflection data in several test areas in Germany with high-resolution digital terrain model (DTM) data (10–50 m resolution) available. These considerable advancements motivate a new analysis of the method of astronomical-topographic levelling, which uses DTM data for the interpolation between the astrogeodetic stations. We present and analyse a least-squares collocation technique that uses DTM data for the accurate interpolation of vertical deflection data. The combination of both data sets allows a precise determination of the gravity field along profiles, even in regions with a rugged topography. The accuracy of the method is studied with particular attention on the density of astrogeodetic stations. The error propagation rule of astronomical levelling is empirically derived. It accounts for the signal omission that increases with the station spacing. In a test area located in the German Alps, the method was successfully applied to the determination of a quasigeoid profile of 23 km length. For a station spacing from a few 100 m to about 2 km, the accuracy of the quasigeoid was found to be about 1–2 mm, which corresponds to a relative accuracy of about 0.05−0.1 ppm. Application examples are given, such as the local and regional validation of gravity field models computed from gravimetric data and the economic gravity field determination in geodetically less covered regions.     

Forecasting sea level anomalies from TOPEX/Poseidon and Jason-1 satellite altimetry

This paper aims at the prediction of both global mean sea level anomalies (SLAs) and gridded SLA data in the east equatorial Pacific obtained from TOPEX/Poseidon and Jason-1 altimetric measurements. The first prediction technique (denoted as LS) is based on the extrapolation of a polynomial-harmonic deterministic least-squares model describing a linear trend, annual and semi-annual oscillations. The second prediction method (denoted as LS + AR) is a combination of the extrapolation of a polynomial-harmonic model with the autoregressive forecast of LS residuals. In the case of forecasting global mean SLA data, both techniques allow one to compute the predictions of comparable accuracy (root mean square error for 1-month in the future is of 0.5 cm). In the case of predicting gridded SLA data, the LS + AR prediction method gains significantly better prediction accuracy than the accuracy obtained by the LS technique during El Niño 1997/1998, La Niña 1998/1999 and during normal conditions.     

全球及局部海洋扰动重力反演的快速解析方法

从经典边值问题理论及球谐函数理论出发,在空域推导获得了由大地水准面高以及垂线偏差计算扰动重力的解析计算公式,为利用卫星测高数据反演海洋扰动重力提供了理论基础。针对全球海洋区域和局部海洋区域的扰动重力反演,在前人已有工作基础上,提出了改进的基于一维FFT的精确快速算法,保证了计算结果与原解析方法完全一致,且计算速度提高约20倍。该算法在提高计算效率的同时避免了由于引入FFT而产生的混叠、边缘效应问题,而且对观测数据的序列长度没有硬性要求,使得应用更加灵活。利用EGM2008地球重力场模型分别生成了2.5'分辨率大地水准面高数据和垂线偏差数据,按照本文提出的改进方法(采用全球积分计算)分别反演获得了全球及局部海洋区域的扰动重力。经比较分析,由大地水准面和垂线偏差分别反演获得的扰动重力其差异在0.8×10^-5 m/s²以内,这说明两种反演方法是基本一致的,但在数据包含系统误差的情况下,由垂线偏差反演扰动重力具有一定优势。     

地球重力场参数计算程序的设计与应用

根据地球重力场参数的计算模型,借助全球地球重力场模型EGM2008,利用Microsoft Visual Studio 2010面向对象的功能,设计和开发了可以计算任意点重力异常、高程异常、垂线偏差分量的计算程序,以德国地学中心(GFZ)研制的相关软件对程序的正确性进行了验证,以吉林省各城市的经纬度数据计算了对应的重力异常、高程异常、垂线偏差分量。     

利用残差地形模型空域法精化局部地球重力场

陆地高分辨率重力数据是超高阶重力场模型及其应用研究的基础,但现有的观测技术和手段限制了陆地重力测量的覆盖区域,全球仍有大量的重力测量空白地区.采用残差地形模型空域法,利用高通滤波技术提取航天飞机雷达地形测绘任务(shuttle radar topography mission,SRTM)分辨率3"×3"的V4.1数据短...     

卫星测高数据的沿轨迹重力异常反演法及其应用

本文给出了一套基于直角坐标系下的垂线偏差求解重力异常公式 ,并将之发展成为一套新的沿轨迹重力异常求解公式。与其他方法相比 ,本方法无须求解交叠点处沿轨迹和跨轨迹方向的海面高斜率 ,仅需计算沿轨迹方向的海面高斜率 ,因而更为简洁、有效 ,而且分辨率可以更高并可与真正的沿航迹实际船测重力相比较、验证。据此 ,利用 Geosat/GM、ERS-1 /35天及TOPEX/Poseidon三种测高数据 ,反演了南中国海域 (0°～ 2 5°N,1 0 5°～ 1 2 2°E)的 2′× 2′重力异常—— IGG-S。通过与实际船测资料和国际同行提供的重力模型相比 ,IGG-S总体精度达到1 0× 1 0 - 5ms- 2。     

北部湾经济区陆海统一似大地水准面精化关键技术研究北大核心CSCD

针对北部湾经济区生态文明建设、海洋资源利用和海洋应急救援事件处置等缺乏统一的陆海高程基准等难题,本文首先利用广西北部湾经济区2764项重力数据和8项GNSS水准数据,应用第二类Helmert凝聚法,反演得到广西北部湾海域及沿大陆海岸线向内陆延伸约15 000 km^(2)区域内置信度较高的重力似大地水准面;然后参考重力场选取EIGEN6C4模型,重力似大地水准面对比8项GNSS水准资料,其精度达2.2 cm;最后采用球冠调和分析方法,将2′×2′格网似大地水准面精度提高至1.6 cm,并将陆地高程基准传递到广西北部湾海域及其海岛上,实现该区域陆海高程基准的统一。     

TRIGONOMETRICAL LEVELLING ACROSS THE INLAND ICE IN NORTH GREENLAND

Abstract

As part of the scientific work of the British North Greenland Expedition (1952–1954), a programme of trigonometrical levelling was carried out from the east to the west coast of Greenland, along a line across the inland ice between latitudes 76° 40′ N., and 78° 10′ N. The primary purpose of the work was to determine accurately the heights above sea level of a series of gravity stations, the gravity measurements being made in connection with determinations of ice thickness. For meteorological purposes it was necessary to know also the altitude of the Expedition's central station, situated in latitude 78° 04′ N., longitude 38° 29′ W. The accuracy necessary for the purpose of the gravity survey was a few metres for the altitudes, while the latitude of each gravity station had to be determined with an accuracy of ± 0.1 minute.     

重力场对惯性导航定位误差影响研究与仿真

从惯性导航力学编排方程出发,将高阶重力场模型代替正常重力模型,分析了扰动重力引起的惯性导航误差;并从另一角度,对理想状态下扰动重力对惯性导航的影响进行了仿真分析,结果表明扰动重力影响显著。通过将重力垂线偏差分量引入惯性导航方程,改善传统方程的缺陷,探讨了垂线偏差对惯性导航的影响。在全面论述了扰动重力和重力垂线偏差对惯性导航的影响的基础上,结合实际情况提出了进行重力场误差补偿的两种方法。     

Global mean sea surface and marine gravity anomaly from multi-satellite altimetry: applications of deflection-geoid and inverse Vening Meinesz formulae

 Global mean sea surface heights (SSHs) and gravity anomalies on a 2^′×2^′ grid were determined from Seasat, Geosat (Exact Repeat Mission and Geodetic Mission), ERS-1 (1.5-year mean of 35-day, and GM), TOPEX/POSEIDON (T/P) (5.6-year mean) and ERS-2 (2-year mean) altimeter data over the region 0^∘–360^∘ longitude and –80^∘–80^∘ latitude. To reduce ocean variabilities and data noises, SSHs from non-repeat missions were filtered by Gaussian filters of various wavelengths. A Levitus oceanic dynamic topography was subtracted from the altimeter-derived SSHs, and the resulting heights were used to compute along-track deflection of the vertical (DOV). Geoidal heights and gravity anomalies were then computed from DOV using the deflection-geoid and inverse Vening Meinesz formulae. The Levitus oceanic dynamic topography was added back to the geoidal heights to obtain a preliminary sea surface grid. The difference between the T/P mean sea surface and the preliminary sea surface was computed on a grid by a minimum curvature method and then was added to the preliminary grid. The comparison of the NCTU01 mean sea surface height (MSSH) with the T/P and the ERS-1 MSSH result in overall root-mean-square (RMS) differences of 5.0 and 3.1 cm in SSH, respectively, and 7.1 and 3.2 μrad in SSH gradient, respectively. The RMS differences between the predicted and shipborne gravity anomalies range from 3.0 to 13.4 mGal in 12 areas of the world's oceans. Received: 26 September 2001 / Accepted: 3 April 2002 Correspondence to: C. Hwang Acknowledgements. This research is partly supported by the National Science Council of ROC, under grants NSC89-2611-M-009-003-OP2 and NSC89-2211-E-009-095. This is a contribution to the IAG Special Study Group 3.186. The Geosat and ERS1/2 data are from NOAA and CERSAT/France, respectively. The T/P data were provided by AVISO. The CLS and GSFC00 MSS models were kindly provided by NASA/GSFC and CLS, respectively. Drs. Levitus, Monterey, and Boyer are thanked for providing the SST model. Dr. T. Gruber and two anonymous reviewers provided very detailed reviews that improved the quality of this paper.     

联合GRACE/GOCE重力场模型和GPS/水准数据确定我国85高程基准重力位

GRACE、GOCE卫星重力计划的实施,对确定高精度重力场模型具有重要贡献。联合GRACE、GOCE卫星数据建立的重力场模型和我国均匀分布的649个GPS/水准数据可以确定我国高程基准重力位,但我国高程基准对应的参考面为似大地水准面,是非等位面,将似大地水准面转化为大地水准面后确定的大地水准面重力位为62 636 854.395 3m~2s~(-2),为提高高阶项对确定大地水准面的贡献,利用高分辨率重力场模型EGM2008扩展GRACE/GOCE模型至2190阶,同时将重力场模型和GPS/水准数据统一到同一参考框架和潮汐系统,最后利用扩展后的模型确定的我国大地水准面重力位为62 636 852.751 8m~2s~(-2)。其中组合模型TIM_R4+EGM2008确定的我国85高程基准重力位值62 636 852.704 5m~2s~(-2)精度最高。重力场模型截断误差对确定我国大地水准面的影响约16cm,潮汐系统影响约4~6cm。     

利用Abel-Poisson径向基函数模型化局部重力场

多种类型高分辨率重力场数据的不断增加,使得在局部范围内精化重力场模型成为了可能。本文采用Abel-Poisson核将重力场量表示成有限个径向基函数线性求和的形式,对局部区域的多种重力场数据进行联合建模。为了提高运算速度,运用了基于自适应精化格网算法的最小均方根误差准则(RMS)来求解径向基函数平均带宽。以南海核心地区为例,联合两种不同类型、不同分辨率的重力场资料(大地水准面起伏6'×6'、重力异常2'×2'),构建了局部区域高分辨率的重力场模型。所建模型表示的重力场参量达到了2'×2'的分辨率,对原始的重力异常数据(2'×2')拟合的符合程度达到±0.8×10-5m/s2。结果表明,利用径向基函数方法进行局部重力场建模,避免了球谐函数建模收敛慢的问题,有效提高了模型表示重力场的分辨率。