Phase Resolved Wave Prediction From Synthetic Radar Images

2014 ◽  
Author(s):  
P. Naaijen ◽  
A. P. Wijaya
Keyword(s):  
Wave Field ◽  
Significant Wave Height ◽  
Sea Surface ◽  
Radar Images ◽  
Wave Prediction ◽  
Wave Elevation ◽  
Linear Waves ◽  
Directional Wave ◽  
2D Fft ◽  
Linear Propagation

A method is presented for the inversion of images of the sea surface taken by nautical radar into wave elevation that is specifically suitable for the prediction of the wave elevation outside the observation domain covered by the radar. By means of a beam-wise analysis of the image obtained by a scanning radar, the image information is translated into wave elevation. Subsequently a 2D FFT is applied in order to obtain the directional wave components required for a linear propagation of the wave field. Assuming knowledge of the significant wave height, a method to obtain the correct scaling of the wave prediction is proposed. The proposed method is verified using synthetic radar images which are modelled by applying shadowing and tilt effect to synthesised short crested linear waves.

Significant wave height estimation using SVR algorithms and shadowing information from simulated and real measured X-band radar images of the sea surface

2015 ◽  
Vol 101 ◽  
pp. 244-253 ◽  
Author(s):  
S. Salcedo-Sanz ◽  
J.C. Nieto Borge ◽  
L. Carro-Calvo ◽  
L. Cuadra ◽  
K. Hessner ◽  
...  
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Sea Surface ◽  
Height Estimation ◽  
Significant Wave ◽  
Radar Images ◽  
X Band

Dynamic Averaging Method to Detect Sea Surface Current From Radar Images

2017 ◽  
Author(s):  
Andreas P. Wijaya
Keyword(s):  
Dispersion Relation ◽  
Current Velocity ◽  
Synthetic Data ◽  
Additional Term ◽  
Surface Current ◽  
Peak Frequency ◽  
Sea Surface ◽  
Radar Images ◽  
Linear Waves ◽  
The Difference

One important parameter in reconstructing and predicting the sea surface elevation from radar images is the surface current. The common method to derive the current is based on 3DFFT with which the (absolute) frequency is derived from a series of images and is fitted to the encounter dispersion relation that consist of the intrinsic exact dispersion relation for linear waves with an additional term that contains the current velocity to be found. The derived dispersion relation will be inaccurate because the images contain many inaccuracies from noise, shadowing, and other radar effects. This paper proposes an alternative method to determine the surface current. Following the method of the Dynamic Averaging and Evolution Scenario (DAES) as presented in [1], the idea is to choose the current velocity that minimizes the difference between an image at a previous time that has been evolved to the time of another image. In order to reduce inaccuracies, an averaging procedure over various images is applied. The method is tested on synthetic data to quantify the accuracy of the results. The robustness of the method will be investigated for several cases of different current parameters (speed and direction) for ensembles of seas with different peak frequency of characteristic sea states.

scholarly journals Directional Coherent Wave Group From an Assimilated Non-linear Wavefield

2021 ◽  
Vol 9 ◽  
Author(s):  
Takuji Waseda ◽  
Shogo Watanabe ◽  
Wataru Fujimoto ◽  
Takehiko Nose ◽  
Tsubasa Kodaira ◽  
...  
Keyword(s):  
Wave Field ◽  
Wave Model ◽  
Linear Wave ◽  
Wave Group ◽  
Wave Groups ◽  
Radar Images ◽  
Coherent Wave ◽  
Non Linear ◽  
Directional Wave ◽  
Reconstructed Wave

The presence of coherent wave groups in the ocean has been so far postulated but still lacks evidence other than the indication from the radar images. Here, we attempt to reconstruct a wave field to monitor the evolution of a directional wave group based on a phase resolving two-dimensional non-linear wave model constrained by the stereo images of the ocean surface. The reconstructed wave field of around 20 wavelength squared revealed a coherent wave group compact in both propagating and transverse directions. The envelope of the wave group seems to be oriented obliquely to the propagation direction, somewhat resembling the directional soliton that was theoretically predicted and experimentally and numerically reproduced recently. A comparison with a constrained linear wave model demonstrated the coherence of the non-linear wave group that propagates for tens of wavelengths. The study elaborates a possibility of a spatially coherent short crested wave group in the directional sea.

High-Resolution Imaging of the Ocean Surface Backscatter by Inversion of Altimeter Waveforms

2011 ◽  
Vol 28 (8) ◽  
pp. 1050-1062 ◽  
Author(s):  
Jean Tournadre ◽  
Bertrand Chapron ◽  
Nicolas Reul
Keyword(s):  
High Resolution ◽  
Significant Wave Height ◽  
Basic Assumption ◽  
Sea Surface ◽  
Small Scale ◽  
High Resolution Imaging ◽  
Small Islands ◽  
Backscatter Coefficient ◽  
High Resolution Images ◽  
Resolution Imaging

Abstract This paper presents a new method to analyze high-resolution altimeter waveforms in terms of surface backscatter. Over the ocean, a basic assumption of modeling altimeter echo waveforms is to consider a homogeneous sea surface within the altimeter footprint that can be described by a mean backscatter coefficient. When the surface backscatter varies strongly at scales smaller than the altimeter footprint size, such as in the presence of surface slicks, rain, small islands, and altimeter echoes can be interpreted as high-resolution images of the surface whose geometry is annular and not rectangular. A method based on the computation of the imaging matrix and its pseudoinverse to infer the surface backscatter at high resolution (~300 m) from the measured waveforms is presented. The method is tested using synthetic waveforms for different surface backscatter fields and is shown to be unbiased and accurate. Several applications can be foreseen to refine the analysis of rain patterns, surface slicks, and lake surfaces. The authors choose here to focus on the small-scale variability of backscatter induced by a submerged reef smaller than the altimeter footprint as the function of tide, significant wave height, and wind.

A Fast Generation Algorithm of Radar Images for Ships on Time-evolving Sea Surface

2021 ◽  
Author(s):  
Dandan Gu ◽  
Pengcheng Gao ◽  
Zhijie Xie ◽  
Wei Gao ◽  
Yan Du ◽  
...  
Keyword(s):  
Sea Surface ◽  
Generation Algorithm ◽  
Radar Images

Towards Nonlinear Wave Reconstruction and Prediction From Synthetic Radar Images

2016 ◽  
Author(s):  
A. P. Wijaya
Keyword(s):  
Vertical Direction ◽  
Sea Surface ◽  
Sea State ◽  
Operational Effectiveness ◽  
State Reconstruction ◽  
Radar Images ◽  
First Results ◽  
Marine Radar ◽  
Offshore Activities

The use of remotely wave sensing by a marine radar is increasingly needed to provide wave information for the sake of safety and operational effectiveness in many offshore activities. Reconstruction of radar images needs to be carried out since radar images are a poor representation of the sea surface elevation: effects like shadowing and tilt determine the backscattered intensity of the images. In [1], the sea state reconstruction and wave propagation to the radar has been tackled successfully for synthetic radar images of linear seas, except for a scaling in the vertical direction. The determination of the significant wave height from the shadowed images only has been described in [2]. This paper will summarize these methods, and provides the first results for the extension to nonlinear seas.

Generation of a spatially periodic directional wave field in a rectangular wave basin based on higher-order spectral simulation

2018 ◽  
Vol 169 ◽  
pp. 428-441 ◽  
Author(s):  
Hidetaka Houtani ◽  
Takuji Waseda ◽  
Wataru Fujimoto ◽  
Keiji Kiyomatsu ◽  
Katsuji Tanizawa
Keyword(s):  
Wave Field ◽  
Higher Order ◽  
Spectral Simulation ◽  
Rectangular Wave ◽  
Wave Basin ◽  
Spatially Periodic ◽  
Directional Wave
Sign in / Sign up

Export Citation Format

Share Document