Improvement in the Determination of the Marine Geoid by Estimating the Bathymetry from Altimetry and Depth Soundings

Abstract

The contribution of bathymetry to the estimation of gravity field related quantities is investigated in an extended test area in the Mediterranean Sea. The region is located southwest of the island of Crete, Greece, bounded between 33^? ≤ ? ≤ 35^? and 15^? ≤ λ ≤ 25^?. Gravity anomalies from the KMS99 gravity field and shipborne depth soundings are used with a priori statistical characteristics of depths in a least-squares collocation procedure to estimate a new bathymetry model. Two different global bathymetry models, namely JGP95E and Sandwell and Smith V8, are used to derive the depth a priori statistical information, while the estimated model is compared against both the global ones and the shipborne depth soundings to assess whether there is an improvement. Various marine geoid models are estimated using ERS1 and GEOSAT Geodetic Mission altimetry and shipborne gravity data. In that process, the effect of the bathymetry is computed using both the estimated and the original depths through a residual terrain modeling reduction. The TOPEX/Poseidon Sea Surface Heights, known for their high accuracy and precision, and the GEOMED solution for the geoid in the Mediterranean are used as control for the validation of the new geoid models and to assess the improvement that the estimated depths offer to geoid modeling. The results show that the newly estimated bathymetry agrees better (by about 30 to 300 m) with the shipborne depth soundings and provides smoother residual geoid heights and gravity anomalies (by about 8–20%) than those from global models. Finally, the achieved accuracy in geoid modeling ranges between 6 and 10 cm (1σ).     

基于半经验模型的水深反演及不同水深范围的误差分析

基于半经验遥感模型,开展广东省雷州湾SPOT-5影像不同水深范围的遥感反演及误差分析,给出不同模型对应的最佳水深范围和不同水深范围的最佳反演模型,结果如下：红光单波段模型、红光-绿光双波段模型、绿光-红光-近红外三波段模型均在2～5m水深范围内反演误差最小,分别为16.7%,13.2%和17.1%。0～2m水深范围内,红光-近红外双波段模型反演误差最小,为34.3%;2～5m水深范围内,红光-绿光双波段模型反演误差最小,为13.2%;5～10m水深范围内,红光-近红外双波段模型反演误差最小,为19.3%;10～20m水深范围内,三波段模型反演误差最小,为31.5%。     

基于Landsat-8遥感影像和LiDAR测深数据的水深主被动遥

主被动遥感结合反演远海岛礁周边水深信息,不仅可以有效弥补传统测深方法覆盖范围小且费时费力的不足,也可为航运安全、海洋减灾、生态环境保护等领域提供基础资料。以夏威夷瓦胡岛周边水深反演为例,应用Landsat-8多光谱遥感数据和机载Li DAR测深数据,开展了不同密度Li DAR测深数据对水深多光谱遥感反演精度的影响分析、不同水深网格化处理方法对水深遥感反演结果的影响分析和基于少量Li DAR控制区块的大区域水深反演能力分析三方面的研究工作。结果表明:(1)Li DAR测深数据密度的改变对水深反演结果的影响不大,变化后的水深反演结果与原始的水深反演结果相比,平均相对误差变化在0.3%以内,平均绝对误差变化在0.03m以内;(2)采用均值格网处理方法的多光谱遥感水深反演精度要略高于采用中值格网处理方法的水深反演精度,具体体现在均值的平均绝对误差要比中值的低0.04~0.05 m,平均相对误差低1%~10%,反演结果的残差分布显示在0~2 m和20~25 m的水深段内均值统计法的残差分布更集中且其平均值接近于0 m,而在其它水深段二者的残差分布基本相同;(3)基于少量Li DAR控制区块的大区域遥感水深反演结果较为理想,两个检查区块的水深反演结果 R2、平均绝对误差和平均相对误差分别为:0.877,1.66 m,3.5%和0.941,1.62 m,28.4%。反演结果分段分析表明各水深段内反演的精度都比较理想,平均绝对误差除20~25 m水深段外,均低于2.5 m,平均相对误差除0~2 m,2~5 m外,均低于25%。     

The Role of Multi-Mission ERS Altimetry in the Determination of the Marine Geoid in the Azores

This study concerns the determination of a regional geoid model in the North Atlantic area surrounding the Azores islands by combining multi-mission altimetry from the ERS (European Remote Sensing) satellites and surface gravity data. A high resolution mean sea surface, named AZOMSS99, has been derived using altimeter data from ERS-1 and ERS-2 35-day cycles, spanning a period of about four years, and from ERS-1 geodetic mission. Special attention has been paid to data processing of points around the islands due to land contamination on some of the geophysical corrections. A gravimetric geoid has been computed from all available surface gravity, including land and sea observations acquired during an observation campaign that took place in the Azores in October 1997 in the scope of a European and a Portuguese project. Free air gravity anomalies were derived by altimetric inversion of the mean sea surface heights. These were used to fill the large gaps in the surface gravity and combined solutions were computed using both types of data. The gravimetric and combined solutions have been compared with the mean sea surface and GPS (Global Positioning System)-levelling derived geoid undulations in five islands. It is shown that the inclusion of altimeter data improves geoid accuracy by about one order of magnitude. Combined geoid solutions have been obtained with an accuracy of better than one decimetre.     

The Role of Multi-Mission ERS Altimetry in the Determination of the Marine Geoid in the Azores

This study concerns the determination of a regional geoid model in the North Atlantic area surrounding the Azores islands by combining multi-mission altimetry from the ERS (European Remote Sensing) satellites and surface gravity data. A high resolution mean sea surface, named AZOMSS99, has been derived using altimeter data from ERS-1 and ERS-2 35-day cycles, spanning a period of about four years, and from ERS-1 geodetic mission. Special attention has been paid to data processing of points around the islands due to land contamination on some of the geophysical corrections. A gravimetric geoid has been computed from all available surface gravity, including land and sea observations acquired during an observation campaign that took place in the Azores in October 1997 in the scope of a European and a Portuguese project. Free air gravity anomalies were derived by altimetric inversion of the mean sea surface heights. These were used to fill the large gaps in the surface gravity and combined solutions were computed using both types of data. The gravimetric and combined solutions have been compared with the mean sea surface and GPS (Global Positioning System)-levelling derived geoid undulations in five islands. It is shown that the inclusion of altimeter data improves geoid accuracy by about one order of magnitude. Combined geoid solutions have been obtained with an accuracy of better than one decimetre.     

Geoid from geopotential model in the Taiwan area

The geoid undulation on GRS80 in the Taiwan area at half‐degree grid points has been calculated using the reduced 30’ × 30’ block mean gravity anomalies and the OSU91A geopotential coefficient set up to degree and order 360. The OSU91A results have been used to compare with WGS84, CEM10C, and OSU86F geoid undulations determined in 18 first‐order triangulation stations of the Taiwan Geodetic Datum 1980 (TGD80). Comparisons have also been made between these free‐air anomalies determined from OSU91A, and terrestrial gravity anomalies. It has been found that the average difference between the OSU91A model‐derived, and 243 actual point free‐air anomalies is 16.8 ± 48.0 mgal. It has also been found that more reliable and dense terrestrial gravity data are needed, both for terrestrial observations and for the OSU91A model, to achieve the very high‐precision geoid on GRS80 in the area of study.     

多波束测深趋势面系数的主成分估计

在多波束测深趋势面滤波构建趋势面模型的过程中,其模型变量线性相关时,系数阵存在复共线性,因此将主成分估计的方法应用于趋势面模型系数的求解,从而避免了复共线性的影响,最后通过实测数据进行实验,分别利用最小二乘算法和主成分估计求解二次趋势面模型。比较计算结果,验证了主成分估计算法的有效性。     

卫星测高技术应用研究回顾与展望

简要介绍了笔者所在单位近十年来密切跟踪世界发展动态,灵活运用高新技术,致力于卫星测高技术应用研究所取得的一些有理论意义和实用价值的成果,这些成果主要包括四个方面：卫星测高径向轨道误差时域和空域特征分析、卫星测高反演海洋重力场、卫星测高反演海底地形以及利用测高重力异常扩展超高阶地球位模型研究成果。最后对这一研究领域未来的发展方向作了展望。     

输入—输出系统理论在重力场扰动场元推估中的应用分析

研究了输入—输出系统理论用于扰动场元推估的一般形式,以重力异常推估大地水准面为例,推导了双输入—单输出系统用于重力场推估的具体形式。通过实际算例表明：输入—输出系统在推估效果上等效于最小二乘配置,利用局部重力异常推估大地水准面的精度在0.4m左右。     

渤海岸线及水深变化对水动力影响的数值模拟

为探究渤海岸线及水深变化对水动力的影响,基于Delft3D水动力学模型,选用2003年和2015年作为围 填海前后的典型年份,建立了围填海前后岸线及水深条件下的渤海三维水动力模型,并对水动力场进行了模拟。通过对围填海前后潮波和潮余流的分析,得到了岸线及水深变化对渤海水动力场的影响。结果表明:填海后,岸线及水深变化会对渤海主导分潮M₂分潮产生较大影响,秦皇岛附近无潮点向西北方向偏移,渤海海域M₂ 分潮振幅总体减小;潮致余流场受岸线及水深变化影响较大,其中渤海湾曹妃甸港南部形成复杂的涡流,沿岸海域余流增大;滨海新区附近形成多个小范围环流,且天津港到黄骅港北部沿岸海域2015年余流比2003年增加3~5 cm/s;黄骅港南部形成一个逆时针环流,并且该处余流减小2~5 cm/s。辽东湾辽河口附近由于水深增加导致余流减小2~7 cm/s。莱州湾黄河口附近的逆时针环流向东南方向移动,黄河口北部余流略有减小,东南部余流明显增大,增加量最多能达到9 cm/s。刁龙嘴南侧顺时针环流减小,北侧顺时针环流增大4~9 cm/s。     

集合调整卡尔曼滤波方法在M2分潮数值模拟中的水深估计研究

数据同化利用观测信息对模型状态场调整的同时也可以对数值模型中的不确定参数进行估计,从而改进数值模型,提高数值模拟的精度。本文基于集合调整卡尔曼滤波方法,采用广义坐标系统的美国普林斯顿大学海洋模式的外模式开展了渤海和部分黄海海域M₂分潮模拟中的水深估计研究。理想数据同化试验结果表明,集合调整卡尔曼滤波方法能很好地降低模式模拟的水位误差并反演出“真实”的水深参数。而在NAO.99Jb和验潮站数据的实际数据同化试验中,与验潮站数据相比较,水深参数估计后,模式模拟的M₂分潮振幅与迟角误差分别降低了40.27%和49.19%。     

Consistency of Geoid Models,Radar Altimetry,and Hydrodynamic Modelling in the North Sea

Radar altimetry, when corrected for tides, atmospheric forcing of the sea surface, and the effects of density variations and mean and time-variable currents, provides an along-track realization of the marine geoid. In this study we investigate whether and how such an ‘altimetric-hydrodynamic’ geoid over the North Sea can serve for validating satellite-gravimetric geoids. Our results indicate that, using ERS-2 and ENVISAT along-track altimetry and water levels from the high-resolution operational circulation model BSHcmod, we do find distinct differences in RMS fits for various state-of-the art satellite-only models (beyond degree 145 for GRACE-only, and beyond degree 185 for GOCE models) and for combined geoid models, very similar as seen in GPS-levelling validations over land areas. We find that, at spectral resolution of up to about 200, an RMS fit as low as about 7 cm can be obtained for the most recent GOCE-derived models such as GOCO05S. This is slightly above what we expect from budgeting individual errors. Key to the validation is a proper treatment of the spectral mismatch between satellite-gravimetric and altimetric-hydrodynamic geoids. Comparison of data fits and error budget suggests that geoid truncation errors residual to EGM2008 (i.e. EGM2008 commission and omission error) may amount up to few cm.     

海洋工程中磁性物质探测时探测间距和探测深度的确定

仿真分析了典型磁性物质磁场分布特征,提出了磁性物质探测间距和探测深度的选择原则,并通过磁探测试验数据对方法有效性进行了验证。结论表明:文中提出的探测间距和探测深度的选择原则是合理的,给出的典型磁性物质探测间距和探测深度的选择方案,可供作业人员参考。     

多类资料计算南海重力垂直梯度的方法比较

重力垂直梯度在解决和解释地球表层地质和地球物理问题中的作用日益明显,因而获得其模型和分布是非常必要的。利用测高卫星可以得到空间大范围高精度、高分辨率的垂线偏差、重力异常以及大地水准面数据,利用测高重力资料和地球重力场模型,采用不同方法分别计算了南海海域重力垂直梯度,并对它们进行了比较。     

黄海海洋环境调查及其主要结果

本文系将我国几十年来在黄海、渤海和东海北部,开展海洋环境调查的情况与主要结果,作一简要回顾。     

海洋磁力测量仪器系统检验方法研究

高精度的海洋磁力测量对磁测仪器系统的测量精度提出了更高的要求,文中对海洋磁力测量仪器系统检验的内容和动静态检验方法进行了研究,并通过实例验证其可行性。结论表明:所提出的仪器系统检验方法可以消除仪器系统误差的影响,提高海洋磁力测量精度,保证成果的可靠性。     

海洋磁力测量仪器系统检验方法研究

高精度的海洋磁力测量对磁测仪器系统的测量精度提出了更高的要求,文中对海洋磁力测量仪器系统检验的内容和动静态检验方法进行了研究,并通过实例验证其可行性。结论表明:所提出的仪器系统检验方法可以消除仪器系统误差的影响,提高海洋磁力测量精度,保证成果的可靠性。     

日照海洋保护区现状及发展对策研究

人类对海洋的青睐和倚重日益凸显为实现海洋未来可持续发展建立海洋保护区是一种有效的预防性海洋综合管理方式。文章根据日照海洋保护区当前发展状况,分析保护区发展中存在的问题,并相应的提出相关建议及对策。希望这些对策能够进一步提高保护区的保护价值。     

海洋经济高质量发展能力评价与提升路径研究

海洋是高质量发展战略要地,推动海洋经济高质量发展是建设海洋强国的必然选择。文章从海洋经济高质量发展的内涵出发,以新发展理念为基础,运用熵权-TOPSIS模型评价沿海地区海洋经济发展质量的综合能力并分析其区域差异。实证结果显示：(1)五大准则层指标按权重从高到低排序依次为：海洋科技创新、对外开放、海洋经济结构、社会民生、海洋生态环境;(2)沿海地区的海洋经济高质量发展水平在考察期间为波动上升趋势,各省(自治区、直辖市)间海洋经济发展质量差距在逐渐变小;(3)影响海洋经济发展质量各子系统中,北部海洋经济圈在5个子系统评分中均处于较低水平。为此,提出促进海洋经济高质量发展的提升路径：海洋科技创新与海洋产业结构升级协同发展、完善海洋生态环境保护政策、打造对外开放新格局等。