Response-Based Estimation of Sea State Parameters

2007 ◽  
Author(s):  
Ulrik D. Nielsen
Keyword(s):  
Closed Form ◽  
Energy Content ◽  
Wave Spectrum ◽  
Final Outcome ◽  
Bayesian Modelling ◽  
Sea State ◽  
Safe Navigation ◽  
Wave Radar ◽  
Frequency Components ◽  
Analytical Expressions

Reliable estimation of the on-site sea state parameters is essential to decision support systems for safe navigation of ships. The sea state parameters can be estimated by Bayesian Modelling which uses complex-valued frequency response functions (FRF) to estimate the wave spectrum on the basis of measured ship responses. It is therefore interesting to investigate how the filtering aspect, introduced by FRF, affects the final outcome of the estimation procedures. The paper contains a study based on numerical generated time series, and the study shows that filtering has an influence on the estimations, since high frequency components of the wave excitations are not estimated as accurately as lower frequency components. Moreover, the paper investigates how the final outcome of the Bayesian Modelling is influenced by the accuracy of the FRF. Thus, full-scale data is analysed by use of FRF calculated by a 3-D time domain code and by closed-form (analytical) expressions, respectively. Based on comparisons with wave radar measurements and satellite measurements it is seen that the wave estimations based on closed-form expressions exhibit a reasonable energy content, but the distribution of energy appears to be incorrect.

scholarly journals An Analytical Method for Dynamic Wave-Related Errors of Interferometric SAR Ocean Altimetry under Multiple Sea States

2021 ◽  
Vol 13 (5) ◽  
pp. 986
Author(s):  
Yao Chen ◽  
Mo Huang ◽  
Yuanyuan Zhang ◽  
Changyuan Wang ◽  
Tao Duan
Keyword(s):  
Electromagnetic Scattering ◽  
Analytical Method ◽  
Wave Spectrum ◽  
High Accuracy ◽  
Sea State ◽  
Error Budget ◽  
Ocean Topography ◽  
Mean Square Errors ◽  
Dynamic Wave ◽  
Wide Swath

The spaceborne interferometric synthetic aperture radar (InSAR) is expected to measure the sea surface height (SSH) with high accuracy over a wide swath. Since centimeter-level accuracy is required to monitor the ocean sub-mesoscale dynamics, the high accuracy implies that the altimetric errors should be totally understood and strictly controlled. However, for the dynamic waves, they move randomly all the time, and this will lead to significant altimetric errors. This study proposes an analytical method for the dynamic wave-related errors of InSAR SSH measurement based on the wave spectrum and electromagnetic scattering model. Additionally, the mechanisms of the dynamic wave-related errors of InSAR altimetry are analyzed, and the detailed numerical model is derived. The proposed analytical method is validated with NASA’s Surface Water and Ocean Topography (SWOT) project error budget, and the Root-Mean-Square Errors (RMSEs) are in good agreement (0.2486 and 0.2470 cm on a 0.5 km2 grid, respectively). Instead of analysis for a typical project, the proposed method can be applied to different radar parameters under multiple sea states. The RMSEs of Ka-band under low sea state, moderate sea state, and high sea state are 0.2670, 1.3154, and 6.6361 cm, respectively. Moreover, the RMSEs of X-band and Ku-band are also simulated and presented. The experimental results demonstrate that the dynamic wave-related errors of InSAR altimetry are not sensitive to the frequencies but are sensitive to the sea states. The error compensation method is necessary for moderate and higher sea states for centimetric accuracy requirements. This can provide feasible suggestions on system design and error budget for the future interferometric wide-swath altimeter.

scholarly journals Sea State Monitoring by Ship Motion Measurements Onboard a Research Ship in the Antarctic Waters

2021 ◽  
Vol 9 (1) ◽  
pp. 64
Author(s):  
Silvia Pennino ◽  
Antonio Angrisano ◽  
Vincenzo Della Corte ◽  
Giampaolo Ferraioli ◽  
Salvatore Gaglione ◽  
...  
Keyword(s):  
Transfer Functions ◽  
Wave Spectrum ◽  
Weather Forecast ◽  
Ship Motion ◽  
State Monitoring ◽  
Sea State ◽  
Peak Period ◽  
Research Ship ◽  
Antarctic Waters ◽  
The Antarctic

A parametric wave spectrum resembling procedure is applied to detect the sea state parameters, namely the wave peak period and significant wave height, based on the measurement and analysis of the heave and pitch motions of a vessel in a seaway, recorded by a smartphone located onboard the ship. The measurement system makes it possible to determine the heave and pitch acceleration spectra of the reference ship in the encounter frequency domain and, subsequently, the absolute sea spectra once the ship motion transfer functions are provided. The measurements have been carried out onboard the research ship “Laura Bassi”, during the oceanographic campaign in the Antarctic Ocean carried out in January and February 2020. The resembled sea spectra are compared with the weather forecast data, provided by the global-WAM (GWAM) model, in order to validate the sea spectrum resembling procedure.

Sea State Estimation Based on Ship Motions Measurements and Data Fusion

2013 ◽  
Author(s):  
Céline Drouet ◽  
Nicolas Cellier ◽  
Jérémie Raymond ◽  
Denis Martigny
Keyword(s):  
Data Fusion ◽  
State Estimation ◽  
Wave Height ◽  
Significant Wave Height ◽  
Wave Spectrum ◽  
Ocean Waves ◽  
Ship Motions ◽  
Sea State ◽  
Significant Wave ◽  
X Band

In-service monitoring can help to increase safety of ships especially regarding the fatigue assessment. For this purpose, it is compulsory to know the environmental conditions encountered: wind, but also the full directional wave spectrum. During the EU TULCS project, a full scale measurements campaign has been conducted onboard the CMA-CGM 13200 TEU container ship Rigoletto. She has been instrumented to measure deformation of the ship as well as the sea state encountered during its trip. This paper will focus on the sea state estimation. Three systems have been installed to estimate the sea state encountered by the Rigoletto: An X-band radar from Ocean Waves with WAMOS® system and two altimetric wave radars from RADAC®. Nevertheless, the measured significant wave height can be disturbed by several external elements like bow waves, sprays, sea surface ripples, etc… Furthermore, ship motions are also measured and can provide another estimation of the significant wave height using a specific algorithm developed by DCNS Research for the TULCS project. As all those estimations are inherently different, it is necessary to make a fusion of those data to provide a single estimation (“best estimate”) of the significant wave height. This paper will present the data fusion process developed for TULCS and show some first validation results.

Low Wave Number Radar Image Energy Influence on Determining Current

2012 ◽  
Vol 433-440 ◽  
pp. 6054-6059
Author(s):  
Gan Nan Yuan ◽  
Rui Cai Jia ◽  
Yun Tao Dai ◽  
Ying Li
Keyword(s):  
Wave Spectrum ◽  
Surface Current ◽  
Sea Surface ◽  
Radar Image ◽  
Wave Number ◽  
Sea State ◽  
Low Frequencies ◽  
In Situ Data ◽  
Main Effects

In the radar imaging mechanism different phenomena are present, as a result the radar image is not a direct representation of the sea state. In analyzing radar image spectra, it can be realized that all of these phenomena produce distortions in the wave spectrum. The main effects are more energy for very low frequencies. This work investigates the structure of the sea clutter spectrum, and analysis the low wave number energy influence on determining sea surface current. Then the radar measure current is validated by experiments. By comparing with the in situ data, we know that the radar results reversed by image spectrum without low wave number spectrum have high precision. The low wave number energy influent determining current seriously.

SCATTERING AND DISSOCIATION OF DEUTERONS AND 3H-NUCLEI BY NUCLEI AT INTERMEDIATE ENERGIES

1995 ◽  
Vol 04 (03) ◽  
pp. 563-586 ◽  
Author(s):  
YU. A. BEREZHNOY ◽  
V. YU. KORDA
Keyword(s):  
Elastic Scattering ◽  
Closed Form ◽  
Cross Sections ◽  
Differential Cross ◽  
Particle System ◽  
Center Of Mass ◽  
Scattering Angle ◽  
Intermediate Energies ◽  
Oscillating Functions ◽  
Analytical Expressions

We present a closed-form description that enables us to obtain the analytical expressions for the elastic scattering and dissociation differential cross-sections of deuterons and 3H-nuclei by heavy target nuclei. The resulting expressions are used to analyze the data for the 110 MeV deuterons elastically scattered on 208Pb-nuclei. The dissociation cross-sections of deuterons and 3H-nuclei are the oscillating functions of the scattering angle of the released two- and three-nucleon-particle system center-of-mass.

scholarly journals NONLINEAR OPTICAL WAVEGUIDE STRUCTURE FOR SENSOR APPLICATION: TM CASE

2007 ◽  
Vol 21 (30) ◽  
pp. 5075-5089 ◽  
Author(s):  
HALA M. KHALIL ◽  
MOHAMMED M. SHABAT ◽  
SOFYAN A. TAYA ◽  
MAZEN M. ABADLA
Keyword(s):  
Refractive Index ◽  
Theoretical Analysis ◽  
Closed Form ◽  
Optical Waveguide ◽  
Effective Refractive Index ◽  
Nonlinear Optical ◽  
Waveguide Structure ◽  
Analytical Expressions ◽  
Evanescent Waveguide ◽  
Waveguide Sensor

In this work, we present an extensive theoretical analysis of nonlinear optical waveguide sensor. The waveguide under consideration consists of a thin dielectrica film surrounded by a self-focused nonlinear cladding and a linear substrate. The nonlinearity of the cladding is considered to be of Kerr-type. Both cases, when the effective refractive index is greater and when it is smaller than the index of the guiding layer, are discussed. The sensitivity of the effective refractive index to any change in the cladding index in evanescent optical waveguide sensor is derived for TM modes. Closed form analytical expressions and normalized charts are given to provide the conditions required for the sensor to exhibit its maximum sensitivity. The results are compared with those of the well-known linear evanescent waveguide sensors.

scholarly journals Operability Guidelines For Product Tanker In Heavy Weather In The Adriatic Sea

2014 ◽  
Vol 21 (1) ◽  
pp. 95-106
Author(s):  
Luka Mudronja ◽  
Marko Katalinić ◽  
Rino Bošnjak ◽  
Pero Vidan ◽  
Joško Parunov
Keyword(s):  
Wave Height ◽  
Adriatic Sea ◽  
Wave Spectrum ◽  
Extreme Weather ◽  
The South ◽  
Sea State ◽  
M Wave ◽  
The North ◽  
Limiting Values ◽  
Deck Wetness

AbstractThis paper presents operability guidelines for seafarers on a product tanker which navigates in the Adriatic Sea during heavy weather. Tanker route starts from the Otranto strait in the south to the island Krk in the north of Adriatic Sea. Heavy weather is caused by south wind called jugo (blowing from E-SE to SS-E, sirocco family). Operability guidelines are given based on an operability criteria platform for presenting ship seakeeping characteristics. Operability criteria considered in this paper are propeller emergence, deck wetness and bow acceleration of a product tanker. Limiting values of mentioned criteria determine sustainable speed. Heavy weather is described by extreme sea state of 7.5 m wave height. Wave spectrum used in this paper is Tabain spectrum which is developed specifically for Adriatic Sea. Seafarer's approach of decisions making in extreme weather is also shown and servers as a guideline for further research of the authors.

Sea State Statistics and Extreme Waves Observed by Satellite

2008 ◽  
Author(s):  
S. Lehner ◽  
J. Schulz-Stellenfleth ◽  
Thomas Ko¨nig ◽  
X. Li
Keyword(s):  
Extreme Events ◽  
Wave Spectrum ◽  
Ocean Waves ◽  
Wave Mode ◽  
Extreme Value Statistics ◽  
Altimeter Data ◽  
Sea State ◽  
Data Set ◽  
Wave Properties ◽  
D Wave

For the design of ships as well as for the investigation of ship accidents it is important to have knowledge about both the two dimensional spectral wave properties as well as extreme value statistics of ocean waves. Although numerical wave models have reached a high level of accuracy, they still have weaknesses with respect to the details of the 2-D wave spectrum. Furthermore standard models like WAM provide estimates of the 2-D wave spectrum, i.e., second order sea state statistics and therefore lack information on individual wave properties and the occurrence of extreme events. In this study the potential of global Synthetic Aperture Radar (SAR) wave mode data acquired by the European satellites ERS-2 and ENVISAT to investigate ship accidents is discussed and compared to altimeter data and ECMWF model results. These data are acquired independent of light and weather conditions on a global scale. A historic data set of ERS-2 wave mode data acquired between 1998 and 2000 is co-located with accidents which occurred during that time. ENVISAT ASAR wave mode data acquired since 2002 are considered, too. Different ocean wave parameters like significant wave height and wave periods are derived from the SAR data. The potential role of the respective wave conditions for some recent accident is discussed in detail. This includes in particular the analysis of cross sea conditions, groupiness and extreme events.

scholarly journals Integrated modelling of sea-state forecasts for safe navigation and operational management in ports: Application in the Mediterranean Sea

2021 ◽  
Vol 89 ◽  
pp. 1206-1234
Author(s):  
Christos Makris ◽  
Yannis Androulidakis ◽  
Theofanis Karambas ◽  
Andreas Papadimitriou ◽  
Anastasios Metallinos ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Integrated Modelling ◽  
Sea State ◽  
Safe Navigation ◽  
Operational Management ◽  
The Mediterranean

Towards a unified framework for maximum wave computation from numerical models: outcomes from the LATEMAR project.

2020 ◽  
Author(s):  
Alvise Benetazzo ◽  
Francesco Barbariol ◽  
Paolo Pezzutto ◽  
Luciana Bertotti ◽  
Luigi Cavaleri ◽  
...  
Keyword(s):  
Numerical Models ◽  
Wave Spectrum ◽  
Wave Model ◽  
Ocean Waves ◽  
Unified Framework ◽  
Sea State ◽  
Large Wave ◽  
Wavewatch Iii ◽  
Wave Models ◽  
The Impact

<p>Reliable prediction of oceanic waves during severe marine storms has always been foremost for offshore platform design, coastal activities, and navigation safety. Indeed, many damaging accidents and casualties during storms were ascribed to the impact with abnormal and unexpected waves. However, predicting extreme wave occurrence is a challenging task, at first, because of their inherent randomness, and because the observation of large ocean waves, of primary importance to assess theoretical and numerical models, is limited by the costs and risks of deployment during severe open-ocean sea-state conditions.</p><p>In the context of the EU-based Copernicus Marine Environment Monitoring Service (CMEMS) evolution, the LATEMAR project (https://www.mercator-ocean.fr/en/portfolio/latemar/) aimed at improving the modelling of large wave events during marine storms. Indeed, at present, operational systems only provide average and peak wave parameters, with no information on individual waves whatsoever. However, developments of the state-of-the-art third-generation wave models demonstrated that using the directional wave spectrum moments into theoretical statistical models for wave extremes, forecasters are able to accurately infer the expected shape and likelihood of the maximum waves during storms.</p><p>The main purpose of the activity is therefore to provide the wave models WAM and WAVEWATCH III with common procedures to explicitly estimate the maximum wave heights for each sea state. LATEMAR achieved this goal by: performing an extensive assessment of the model maximum waves using field observations collected from an oceanographic tower; comparing WAM and WAVEWATCH III maximum wave estimates in the Mediterranean Sea; investigating the sensitivity of the maximum waves on the main sea state parameters. All model developments and evaluations resulting from this research project will be directly applicable to the wave model forecasting systems to expand their catalogue.</p>

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