基于ARMA模型的海洋磁力测量数据小波去噪方法研究

海洋磁力测量是指通过安置在海底质子旋进磁力仪来直接测量地磁场,这样在海洋表面和海底同时测量,就可以得到地磁场的垂直梯度。但处理海洋磁力测量数据时不仅需要消耗大量时间,并且分块处理拼图还会导致精确度较低。为了实现对海洋地质层参数的准确测量,提出基于ARMA模型的海洋磁力测量数据小波去噪方法。构建海洋磁力测量数据的小波降噪和滤波检测模型,通过对海洋磁力测量数据的类型化分类识别,进行多波束的信息分割,实现对海洋磁力测量数据的自动滤波降噪,使得输出数据更清晰、自然。测试结果表明,使用ARMA模型后,输出数据的信噪比较之前提升了33.6632 dB,海洋磁力测量数据去噪效果好。通过ARMA模型对海洋磁力数据进行去噪,有助于达到更精确的海洋磁力测量数据,为研究地磁场及其变化、海洋地质构造、矿产预测和国防建设提供了重要支持。

南海诸岛地理实体及其名称研究

分析了南海诸岛地名的历史和现状,通过比对历史资料和现代精细化海洋测量数据,发现了南海诸岛地理实体特征与其名称关系匹配存在的不足。归纳总结了4个方面问题:①地名指代地理实体的范围不明确或不合理;②部分地理实体名称未对外公布;③新发现的地理实体未被命名;④部分不存在的地理实体未被销名。通过列举多个地名的使用情况,基于精细化测量数据分析地理实体的形态、性质、特征等基础信息,研究了处理方法,制定了解决方案。从新技术应用、建立资源共享机制等方面,对进一步开展南海诸岛地名研究工作提出了建议。

Evaluation of wind vectors observed by HY-2A scatterometer using ocean buoy observations,ASCAT measurements,and numerical model data

The first Chinese microwave ocean environment satellite HY-2A was launched successfully in August, 201 I. This study presents a quality assessment of HY-2A scatterometer （HYSCAT） data based on comparison with ocean buoy data, the Advanced Scatterometer （ASCAT） data, and numerical model data from the National Centers for Environmental Prediction （NCEP）. The in-situ observations include those from buoy arrays operated by the National Data Buoy Center （NDBC） and Tropical Atmosphere Ocean （TAO） project. Only buoys located offshore and in deep water were analyzed. The temporal and spatial collocation windows between HYSCAT data and buoy observations were 30 min and 25 km, respectively. The comparisons showed that the wind speeds and directions observed by HYSCAT agree well with the buoy data. The root-mean-squared errors （RMSEs） of wind speed and direction for the HYSCAT standard wind products are 1.90 m/s and 22.80°, respectively. For the HYSCAT-ASCAT comparison, the temporal and spatial differences were limited to 1 h and 25 km, respectively. This comparison yielded RMSEs of 1.68 m/s for wind speed and 19.1° for wind direction. We also compared HYSCAT winds with reanalysis data from NCEP. The results show that the RMSEs of wind speed and direction are 2.6 m/s and 26°, respectively. The global distribution of wind speed residuals （HYSCAT-NCEP） is also presented here for evaluation of the HYSCAT-retrieved wind field globally. Considering the large temporal and spatial differences of the collocated data, it is concluded that the HYSCAT-retrieved wind speed and direction met the mission requirements, which were 2 rn/s and 20° for wind speeds in the range 2-24 m/s. These encouraging assessment results show that the wind data obtained from HYSCAT will be useful for the scientific community.

Modal Strain Energy Based Structural Damage Localization for Offshore Platform using Simulated and Measured Data

Modal strain energy based methods for damage detection have received much attention. However, most of published articles use numerical methods and some studies conduct modal tests with simple 1D or 2D structures to verify the damage detection algorithms. Only a few studies utilize modal testing data from 3D frame structures. Few studies conduct performance comparisons between two different modal strain energy based methods. The objective of this paper is to investigate and compare the effectiveness of a traditional modal strain energy method(Stubbs index) and a recently developed modal strain energy decomposition(MSED) method for damage localization, for such a purpose both simulated and measured data from an offshore platform model being used. Particularly, the mode shapes used in the damage localization are identified and synthesized from only two measurements of one damage scenario because of the limited number of sensors. The two methods were first briefly reviewed. Next, using a 3D offshore platform model, the damage detection algorithms were implemented with different levels of damage severities for both single damage and multiple damage cases. Finally, a physical model of an offshore steel platform was constructed for modal testing and for validating the applicability. Results indicate that the MSED method outperforms the Stubbs index method for structural damage detection.

Calculation of Significant Wave Height Using the Linear Mean Square Estimation Method

Significant wave height is an important criterion in designing coastal and offshore structures.Based on the orthogonality principle, the linear mean square estimation method is applied to calculate significant wave height in this paper.Twenty-eight-year time series of wave data collected from three ocean buoys near San Francisco along the California coast are analyzed.It is proved theoretically that the computation error will be reduced by using as many measured data as possible for the calculation of significant wave height.Measured significant wave height at one buoy location is compared with the calculated value based on the data from two other adjacent buoys.The results indicate that the linear mean square estimation method can be well applied to the calculation and prediction of significant wave height in coastal regions.

Recovery of Bathymetry from Altimeter Data

At present,there exist two methods used to recover the bathymetry from altimeter data,i.e.the deterministic method and the stochastic method.In this paper,the principles of the two methods are introduced first.Then according to the theory of least_square collocation,a modified statistical model for recovering bathymetry from altimeter data is proposed.The new model has been used for computing the ocean depth in the South China Sea from altimeter_derived gravity anomalies.Finally the predicted depths are compared with the ship_borne depth.It shows that they agree with each other very well.

A Marine Remote Sensing Spatial Database Engine for Web Publishing

To meet the requirements of efficient management and web publishing for marine remote sensing data, a spatial database engine, named MRSSDE, is designed independently. The logical model, physical model, and optimization method of MRSSDE are discussed in detail. Compared to the ArcSDE, which is the leading product of Spatial Database Engine, the MRSSDE proved to be more effective.