海洋卫星测高及其反演全球海洋重力场和海底地形模型研究进展

海洋卫星测高在全球和区域大地水准面建模、全球海洋重力场反演、海底地形探测、海平面变化监测、构造板块运动研究等大地测量领域至关重要。本文概述了海洋微波测高卫星的简要发展历程,重点梳理了卫星测高在全球海洋重力场和全球海底地形建模方面取得的丰硕成果,对比分析了主流的海洋重力场和海底地形模型;介绍了合成孔径雷达高度计、Ka频段雷达高度计、合成孔径雷达干涉仪3种先进微波测高技术,并分析了其各自的优缺点,表明它们将在未来若干年呈并驱发展趋势;较为系统地阐述了海洋卫星测高的另一新型技术,即GNSS反射信号测量技术的研究动态,给出了GNSS-R(GNSS reflectometry)类(试验)卫星的发展脉络和发展前景。卫星测高的发展趋势之一是多颗测高卫星的组网观测,本文概括了曾经提出的和拟议中的若干组网测高计划,扼要介绍了由我国提出并正在实施的双星跟飞测高模式;最后指出了卫星测高发展的几个主要关注点,包括双星跟飞测高和SWOT(surface water ocean topography)任务的2维海面高(差)测量、卫星测高反演海底地形与高级地形激光高度计观测数据及遥感卫星图像的结合、星载GNSS-R厘米级海面高的载波相位测量、人工智能技术在卫星测高中的潜在应用等。     

双星伴飞卫星测高模式及其轨道设计

为达到提高反演海洋重力场分辨率的要求,本文提出一种双星伴飞的测高卫星模式,并根据卫星轨道设计的基本要求,给出相应的卫星轨道设计方案。仿真分析表明,该方案可在卫星设计寿命内完成反演1′×1′空间分辨率海洋重力场的要求,且观测数据覆盖了全球大部分海洋区域。该模式可实现星下点海平面梯度的实时测量,提出了改进测高反演海洋重力场的精度的新思路。     

利用卫星资料研究中国南海海底地形

基于海洋重力异常与海深之间的密切关系 ,推导了利用FFT技术由重力异常计算海深的模型 ;利用该模型联合卫星测高数据和海洋重力资料反演了中国南海 2 .5′× 2 .5′海底地形 ;探讨了各种地球物理信息对于反演海底地形的影响     

联合卫星重力和卫星测高数据确定稳态海洋动力地形

新一代卫星重力探测任务GRACE大大提高了地球重力场模型中长波分量的精度,使得联合卫星测高平均海面分离更精细稳态海洋动力地形成为可能。本文利用T/P(1994年~2003年)和JASON-1(2003年~2005年)卫星测高数据确定了全球30′×30′平均海面高;基于重力场模型WHU-GM-05,计算得到对应于海面高的GRACE海洋大地水准面格网值;利用“移去-恢复法”和高斯滤波求得全球稳态海面地形。与EGM96、R io05、ECCO和GGM02模型进行比较,检验结果表明GRACE任务有效的改善了海洋大地水准面的精度,使得稳态海洋动力地形能够呈现更多细部。     

融合卫星测高和船测重力数据的非均匀密度点质量方法

融合多源海洋重力数据是提升极地、近岸和海底地形复杂区域卫星测高反演海洋重力场模型精度的重要途径.利用国际公开的船测重力数据与测高重力场模型,以琉球群岛附近海域为例,本文分析了点质量密度和船测重力数据分布对点质量模型融合精度的影响,结合船测重力数据分布,构建了基于迭代移去恢复的非均匀密度点质量模型.在相同船测重力约束下,非均匀密度点质量模型融合精度较均匀密度的点质量模型提升可达12％.     

利用卫星测高资料反演海底地形研究

论述了利用卫星测高数据反演海底地形地解析算法和统计算法的基本原理和数学模型，在此基础上，基于最小二乘配置理论，提出了统计算法的改进模型。使用新模型在南中国海地区进行了海底地形反演计算，并将反演结果与实际船测水深进行比对，进一步验证改进模型的可靠性和有效性。     

卫星测高与卫星重力对洋流的研究

卫星技术研究洋流的关键在于高精度高分辨率的海洋大地水准面和高精度的卫星海面高。卫星测高的观测结果包括海洋大地水准面和动态海面地形两部分,根据现有的卫星测高成果分离海洋大地水准面与动态海面地形将是十分困难的,必须与重力卫星获得的高精度海洋大地水     

利用卫星测高资料确定海洋重力场

卫星测高是20世纪末发展起来的新型星地观测技术。它是利用星载雷达测高仪测量卫星到海面的高度、有效渡高和后向散射系数，从而大规模探测海洋重力场、海洋环流、海洋风场、海底地质和地貌等海洋环境信息。西安测绘研究所在国内率先利用Topex／Poseidon、     

利用TOPEX测高数据确定大洋环流模式

大洋环流对海洋学、大地测量学以及地球物理学等学科具有重要意义.介绍了利用卫星测高确定海面地形和大洋环流的原理与方法,利用6年的TOPEX测高数据计算了平均稳态海面地形模型,并将其与EGM96、CSR以及Levitus(1982)海面地形模型进行了比较,在此基础上对平均大洋环流模式进行了初步的研究.     

中国海及邻近海域2′×2′海底地形

利用由Seaset、Geosat、ERS_1和Topex/Poseidon卫星测高结果解算的 2′× 2′重力资料进行重力场分离 ,提取与海底地形起伏相关的重力异常 ,结合 5′× 5′ETOPO5海底地形资料进行反演 ,得到了中国海及邻域 2′× 2′高精度、高分辨率的海底地形结果。     

超高阶地球位模型的计算与分析

全球重力场模型是当今物理大地测量学最为活跃的研究领域之一。本文基于目前国内外最新的重力场模型理论研究成果 ,提出了利用中国地区细部数据和全球卫星测高 2′× 2′网格重力异常扩展超高阶位模型的计算方法 ,详细讨论了数值解算过程中的稳定性和可靠性问题。以 EGM96和 GPM98CR模型作为参考模型 ,在全球意义上分别解算得到 MOD99a( 360阶 )、MOD99b( 72 0阶 )和 MOD99c/d( 1 80 0阶 ) ,将系列模型 MOD99a/b/c/d同中国地区 72个 GPS水准大地水准面和全球海洋 1 2个地区的卫星测高大地水准面进行了比较 ,并通过功率谱分析方法检验了 4组模型的有效性和可靠性。     

Gravity-field improvement in the Mediterranean Sea by estimating the bottom topography using collocation

The contribution of bathymetry to the prediction of quantities related to the gravity field (e.g., gravity anomalies, geoid heights) is discussed in an extended test area of the central Mediterranean Sea. Sea gravity anomalies and a priori statistical characteristics of depths are used in a least-squares collocation procedure in order to produce new depths, giving a better smoothing of the gravity field when using a remove-restore procedure. The effect of the bottom topography on gravity-field modeling is studied using both the original and the new depths through a residual terrain modeling reduction. The numerical tests show a considerable smoothing of the sea gravity anomalies and the available altimeter heights when the new depth information is taken into account according to the covariance analysis performed. Moreover, geoid heights are computed by combining the sea gravity anomalies either with the original depths or with the new ones, using as a reference surface the OSU91A geopotential model. Comparing the computed geoid heights with adjusted altimeter sea-surface heights (SSHs), better results are obtained when subtracting the attraction of the new depth information. Similar results are obtained when predicting gravity anomalies from altimeter SSHs where the terrain effect on altimetry is based on the new bottom topography. Received: 10 September 1996 / Accepted: 4 August 1997     

Regional geoid of the Weddell Sea,Antarctica, from heterogeneous ground-based gravity data

We present a geoid solution for the Weddell Sea and adjacent continental Antarctic regions. There, a refined geoid is of interest, especially for oceanographic and glaciological applications. For example, to investigate the Weddell Gyre as a part of the Antarctic Circumpolar Current and, thus, of the global ocean circulation, the mean dynamic topography (MDT) is needed. These days, the marine gravity field can be inferred with high and homogeneous resolution from altimetric height profiles of the mean sea surface. However, in areas permanently covered by sea ice as well as in coastal regions, satellite altimetry features deficiencies. Focussing on the Weddell Sea, these aspects are investigated in detail. In these areas, ground-based data that have not been used for geoid computation so far provide additional information in comparison with the existing high-resolution global gravity field models such as EGM2008. The geoid computation is based on the remove–compute–restore approach making use of least-squares collocation. The residual geoid with respect to a release 4 GOCE model adds up to two meters and more in the near-coastal and continental areas of the Weddell Sea region, also in comparison with EGM2008. Consequently, the thus refined geoid serves to compute new estimates of the regional MDT and geostrophic currents.     

Estimation of dynamic ocean topography in the Gulf Stream area using the Hotine formula and altimetry data

Two modifications of the Hotine formula using the truncation theory and marine gravity disturbances with altimetry data are developed and used to compute a marine gravimetric geoid in the Gulf Stream area. The purpose of the geoid computation from marine gravity information is to derive the absolute dynamic ocean topography based on the best estimate of the mean surface height from recent altimetry missions such as Geosat, ERS-1, and Topex. This paper also tries to overcome difficulties of using Fast Fourier Transformation (FFT) techniques to the geoid computation when the Hotine kernel is modified according to the truncation theory. The derived absolute dynamic ocean topography is compared with that from global circulation models such as POCM4B and POP96. The RMS difference between altimetry-derived and global circulation model dynamic ocean topography is at the level of 25cm. The corresponding mean difference for POCM4B and POP96 is only a few centimeters. This study also shows that the POP96 model is in slightly better agreement with the results derived from the Hotine formula and altimetry data than POCM4B in the Gulf Stream area. In addition, Hotine formula with modification (II) gives the better agreement with the results from the two global circulation models than the other techniques discussed in this paper. Received: 10 October 1996 / Accepted: 16 January 1998     

Slope correction for ocean radar altimetry

We develop a slope correction model to improve the accuracy of mean sea surface topography models as well as marine gravity models. The correction is greatest above ocean trenches and large seamounts where the slope of the geoid exceeds 100  \(\upmu \) rad. In extreme cases, the correction to the mean sea surface height is 40 mm and the correction to the along-track altimeter slope is 1–2  \(\upmu \) rad which maps into a 1–2 mGal gravity error. Both corrections are easily applied using existing grids of sea surface slope from satellite altimetry.     

联合卫星测高和海洋物理数据计算近海稳态海面地形的可行性分析

在系统论的指导下 ,以测量平差中一个浅显的例子作对比 ,巧妙地阐述了联合卫星测高和海洋物理数据计算近海稳态海面地形的可行性 ,进而将可行的计算方案归结为具有本质联系的三类。     

The relation between degree-2160 spectral models of Earth’s gravitational and topographic potential: a guide on global correlation measures and their dependency on approximation effects

Comparisons between high-degree models of the Earth’s topographic and gravitational potential may give insight into the quality and resolution of the source data sets, provide feedback on the modelling techniques and help to better understand the gravity field composition. Degree correlations (cross-correlation coefficients) or reduction rates (quantifying the amount of topographic signal contained in the gravitational potential) are indicators used in a number of contemporary studies. However, depending on the modelling techniques and underlying levels of approximation, the correlation at high degrees may vary significantly, as do the conclusions drawn. The present paper addresses this problem by attempting to provide a guide on global correlation measures with particular emphasis on approximation effects and variants of topographic potential modelling. We investigate and discuss the impact of different effects (e.g., truncation of series expansions of the topographic potential, mass compression, ellipsoidal versus spherical approximation, ellipsoidal harmonic coefficient versus spherical harmonic coefficient (SHC) representation) on correlation measures. Our study demonstrates that the correlation coefficients are realistic only when the model’s harmonic coefficients of a given degree are largely independent of the coefficients of other degrees, permitting degree-wise evaluations. This is the case, e.g., when both models are represented in terms of SHCs and spherical approximation (i.e. spherical arrangement of field-generating masses). Alternatively, a representation in ellipsoidal harmonics can be combined with ellipsoidal approximation. The usual ellipsoidal approximation level (i.e. ellipsoidal mass arrangement) is shown to bias correlation coefficients when SHCs are used. Importantly, gravity models from the International Centre for Global Earth Models (ICGEM) are inherently based on this approximation level. A transformation is presented that enables a transformation of ICGEM geopotential models from ellipsoidal to spherical approximation. The transformation is applied to generate a spherical transform of EGM2008 (sphEGM2008) that can meaningfully be correlated degree-wise with the topographic potential. We exploit this new technique and compare a number of models of topographic potential constituents (e.g., potential implied by land topography, ocean water masses) based on the Earth2014 global relief model and a mass-layer forward modelling technique with sphEGM2008. Different to previous findings, our results show very significant short-scale correlation between Earth’s gravitational potential and the potential generated by Earth’s land topography (correlation +0.92, and 60% of EGM2008 signals are delivered through the forward modelling). Our tests reveal that the potential generated by Earth’s oceans water masses is largely unrelated to the geopotential at short scales, suggesting that altimetry-derived gravity and/or bathymetric data sets are significantly underpowered at 5 arc-min scales. We further decompose the topographic potential into the Bouguer shell and terrain correction and show that they are responsible for about 20 and 25% of EGM2008 short-scale signals, respectively. As a general conclusion, the paper shows the importance of using compatible models in topographic/gravitational potential comparisons and recommends the use of SHCs together with spherical approximation or EHCs with ellipsoidal approximation in order to avoid biases in the correlation measures.     

高分辨率光学卫星影像全球重点区域三维建模方法——以迪拜市为例

针对境外典型区域精细化三维建模数据获取与产品制作技术难点，本文设计归纳出一种高分辨率光学卫星影像精细化三维建模方法。选取迪拜市中心城区为试验区域，以WorldView-3、GeoEye-1等主流高分卫星影像为主要数据源，以互联网众源影像为辅助数据源，利用卫星影像精准定向精化的RPC参数及生成的精准几何信息（DSM/DOM），完成区域内主要建筑物的三维模型生产制作，并形成高分辨率卫星影像三维建模原型系统，满足全球地理信息资源建设与维护更新工程，快速制作符合精度和精细度要求的三维数字模型的需要。