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Proposal To Demonstrate An Hf Radar System For Measuring The Ocean Wave Directional Spectrum From Offshore Platforms
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Book Synopsis Proposal to Demonstrate an HF Radar System for Measuring the Ocean-wave Directional Spectrum from Offshore Platforms by :
Download or read book Proposal to Demonstrate an HF Radar System for Measuring the Ocean-wave Directional Spectrum from Offshore Platforms written by and published by . This book was released on 1981 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Status of HF Radars for Wave-Height Directional Spectral Measurements by : Donald E. Barrick
Download or read book Status of HF Radars for Wave-Height Directional Spectral Measurements written by Donald E. Barrick and published by . This book was released on 1982 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: This manuscript is a concise review of the status of high-frequency (HF) radars for measuring various descriptors of the ocean wave-height directional spectrum. It is not intended as a historical account of the many developments and contributors to the subject over the past three decades, nor is it meant to develop the theory and techniques of HF radar in sufficient detail for planning HF radar programs. Finally, no attempt is made to review every MF/ HF experiment performed or analyzed, although several very clever techniques have been tried (e.g., bistatic arrangements, synthetic aperture systems, and balloon-borne antennas); rather, techniques are discussed that appear to have potential for practical, operational ocean monitoring. The next section reviews very briefly the principles of HF radar sea echo that make it possible to measure the wave-height directional spectrum. The section following discusses the capability and status of sky-wave (over-the-horizon) radar for making wide- area ocean surface measurements. The final section discusses the application of HF ground-wave radars to measuring the wave-height directional spectrum, both for coastal use and for deployment from offshore platforms or ships, and their accuracy. In all cases, the limitations as well as the advantages of HF radars are indicated.
Book Synopsis Prospects for Operational HF Radar Measurements of the Ocean Wave Directional Spectrum by : Lucy Rhiannon Wyatt
Download or read book Prospects for Operational HF Radar Measurements of the Ocean Wave Directional Spectrum written by Lucy Rhiannon Wyatt and published by . This book was released on 1989 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Remote Sensing of the Directional Ocean Wave Spectra Using HF Backscatter Radar by : Abdelrahman M. Elabdalla
Download or read book Remote Sensing of the Directional Ocean Wave Spectra Using HF Backscatter Radar written by Abdelrahman M. Elabdalla and published by . This book was released on 1982 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The High Frequency Surface Wave Radar Cross Section for Ocean Swell by : Chengxi Shen
Download or read book The High Frequency Surface Wave Radar Cross Section for Ocean Swell written by Chengxi Shen and published by . This book was released on 2013 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Analysis Methods for Narrow-beam High-frequency Radar Sea Echo by : Belinda J. Lipa
Download or read book Analysis Methods for Narrow-beam High-frequency Radar Sea Echo written by Belinda J. Lipa and published by . This book was released on 1982 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Remote Sensing of Ocean Surface Current and Current Shear by HF Backscatter Radar by : Eng-Chong Ha
Download or read book Remote Sensing of Ocean Surface Current and Current Shear by HF Backscatter Radar written by Eng-Chong Ha and published by . This book was released on 1979 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Doppler spectrum of radar return from the sea at HF contains two narrow lines displaced upward and downward from the carrier frequency, resulting from backscatter off ocean surface waves moving toward and away from the radar, respectively. These Bragg lines indicate resonant backscatter which occurs for the ocean waves of length one-half the radio wavelength. The phase velocity of these gravity waves consists of two components; the first is determined by the wavelength and the second by the current component in the direction of wave propagation averaged over depth with an exponential weighting function that has a characteristic scale proportional to the wavelength. The Doppler shift of the radar carrier is determined by the wave phase velocity. Its variation with carrier frequency is thus related to the vertical profile of the current component in the radar direction by a Laplace transform; therein lies the principle of radio measurement of ocean current and its vertical shear. Radio backscatter experiments to verify the feasibility of such measurements were conducted using the radar operating at four frequencies covering the range from 3 to 30 MHz. The depth-averaged radial current deduced from the centroid of the Doppler-shifted sea echo experiments at 6.8, 13.3, 21.7, and 29.8 MHz showed fluctuations on the order of 1 cm/sec superimposed on temporal trends that reached maximum values of about 40 cm/sec. It is concluded that multifrequency backscatter ground-wave radar at HF constitutes a powerful technique for mapping current and its vertical profile in the top few meters of the ocean.
Book Synopsis Remote Sensing of Swell and Currents in Coastal Zone by HF Radar by : Weili Wang
Download or read book Remote Sensing of Swell and Currents in Coastal Zone by HF Radar written by Weili Wang and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nearshore marine environment contains many complex processes, but the lack of high-resolution data over a large area during a long time is often the primary obstacle to further research. High-frequency (HF) radar is a mean of remote sensing which obtains continuous near-real time sea surface information over a large area. Thus the study of inversion of marine parameters from HF radar data is very meaningful. Thisthesis makes use of a 13-month-long dataset collected by two phased array HF radar to investigate the characteristics of the sea echo signals, study the data processing and inversion methods, compute sea surface parameters and evaluate the accuracy of radarinversion of swell parameters.The thesis refers to the ground wave HF radar, whose radio waves interact with ocean by Bragg resonance scattering. The development history and applications of HF radar is introduced. The basic theory of electromagnetic wave is reviewed. The principles of inversion of sea surface current, wind direction and swell parameters are described. The feasibility of the swell parameter inversion is investigated. Based on theoretical analysis and statistical studies of a large number of samples, the thesis proposes a series of methods on raw signal processing and quality control, including the determination of the noise level, data averaging in space and time, the proper identification of spectral peaks, the peak width threshold, etc. Respecting the characteristics of different physical processes, inversions of current and wind use spectra collected every 20 min; inversion of swell parameters uses one-hour averaged spectra. The statistics of qualified spectra for swell parameter calculations are presented for both stations. A set of efficient, with a reduced computational cost, automatic computing programs are developed to do the processing and derive marine parameters. Radial current velocities are derived from single radar station. Current vector fields are obtained by combination of both stations. One-year mean flow field in the Iroise Sea is shown, together with the computation of vorticity and divergence. A one-month SeaSonde radar dataset off Qingdao is studied. One-month mean flow pattern together with vorticity and divergence are presented.Relative wind direction with respect to radar look direction is measured through ratio of Bragg peaks amplitudes. Different empirical models are employed to derive radar-inverted relative wind direction. Results show reasonable agreement with model estimations. Different directional distribution models are used to measure the spreading factor for the Iroise Sea. The thesis focuses on the study of swell parameters. Results are validated by buoy and wave model (WAVEWATCH III) data. The assessments show that the accuracy of swell frequency is very good, the accuracy of swell significant waveheight is reasonable, and the accuracy of relative swell direction is low.Consistency of measurements by both radar stations is verified by comparison between the two. This also supports the use of double samples to do the inversion. Use of two radars not only further improves the accuracy but also solves the ambiguity of relative swell direction from single station and gives the absolute wave direction to a certain precision. The thesis proposes a constant relative directionmethod to derive swell significant waveheight, based on the studies of radar integral equation and the inverted results of relative swell direction. This proposal is demonstrated to improve the agreement of radar inversion and buoy/model provided significant waveheight and increases significantly the number of samples. The thesis investigates the accuracy of swell parameters obtained by HF radar. Contributions of random errors in radar observations are quantified. Comparing the differences between radar and buoy/model estimations gives assessments of the contribution of radar intrinsic uncertainty and contribution of other factors.
Book Synopsis Directional Properties of Surface Waves Observed With HF Radar by :
Download or read book Directional Properties of Surface Waves Observed With HF Radar written by and published by . This book was released on 2003 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of the work at Sheffield is to demonstrate that wave measurements obtained using HF radars are of sufficient accuracy and availability for them to contribute to the investigation of changes to the directional spectrum of waves subject to meteorological bathymetric and current variability in coastal environments for both scientific and operational applications. This report summarizes the measurements made with the OSCR HF radar in collaboration with the University of Miami, during the SHOWEX experiment in fall 1999 using inversion algorithms developed at the University of Sheffield. The data set obtained contains interesting examples of shoaling waves and fetch limited wave development but the amount of data obtained was limited by the hardware constraints of the OSCR system. Comparisons with directional wave buoys confirmed the results of earlier work that signal-to-noise and antenna sidelobes are the main sources of error in the radar wave measurements.
Book Synopsis Errors in HF Radar Ocean Current Measurements by : Tatsuya Najima
Download or read book Errors in HF Radar Ocean Current Measurements written by Tatsuya Najima and published by . This book was released on 2005 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Nonlinear Approach to Ocean Wave Spectrum Extraction from Bistatic HF-radar Data by : Murilo Teixeira Silva
Download or read book A Nonlinear Approach to Ocean Wave Spectrum Extraction from Bistatic HF-radar Data written by Murilo Teixeira Silva and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, a new approach to the extraction of the directional ocean wave spectrum from bistatic high frequency (HF) radar data is proposed. The proposed method relies on the simplification of the second-order bistatic radar cross-section, analogous to the one presented by Shahidi and Gill [1] for the monostatic case, to facilitate the use of nonlinear optimization methods, such as regularized nonlinear least-squares. Initially, the historic development of the techniques related to the extraction of the ocean wave spectrum from HF radar data is provided in order to contextualize the work of this thesis. Then, an overview of the theory related to ocean waves and the bistatic radar cross-section is shown. Later, the nonlinear optimization method used in this thesis, Tikhonov regularization in Hilbert spaces, is explained, as well as the theoretical background necessary to understand the method. Once the theory is laid out, the simplification of the second-order bistatic HF radar cross section is presented. The simplification consists of a change of variables that allow the use of the "sifting" property of the Dirac delta function. This reduces the dependence of the second-order bistatic cross-section to a single variable. After the simplification process is shown, the methodology for extracting the directional ocean wave spectrum from bistatic HF radar data is discussed. As a proof-of-concept, the method is initially applied to the second-order bistatic cross section, without the presence of noise. The method successfully extracted the directional ocean wave spectrum without assuming any function model for the nondirectional ocean wave spectrum, and assuming a cosine-power model for the directional spreading function. Next, the first-order bistatic HF radar cross section is added to the second-order cross section, and the proposed method is applied, still without noise present. The proposed method was also able to extract the directional ocean wave spectrum and very low error is added by the inclusion of the first-order cross section. Finally, different levels of noise are added to the cross section including the first and second- orders, and the presented method is applied for the extraction. Again, the method yields good results, with acceptable levels of error for the different noise levels. This new approach to the extraction of the directional ocean wave spectrum from bistatic HF radar data presents, to the author's knowledge, the first nonlinear extraction method for bistatic HF radar data. Further developments of the technique, such as the use of different nonlinear extraction methods, or a general directional spreading function, are suggested.
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 892 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Coastal Ocean Dynamics Applications Radar by : Thomas Martin Georges
Download or read book Coastal Ocean Dynamics Applications Radar written by Thomas Martin Georges and published by . This book was released on 1985 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis An Algorithm for the Extraction of Ocean Wave Parameters from Wide Beam HF Radar (CODAR) Backscatter by : Eric William Gill
Download or read book An Algorithm for the Extraction of Ocean Wave Parameters from Wide Beam HF Radar (CODAR) Backscatter written by Eric William Gill and published by . This book was released on 1990 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Measurement of Ocean Wave Spectra Using a Ship-mounted HF Radar by :
Download or read book Measurement of Ocean Wave Spectra Using a Ship-mounted HF Radar written by and published by . This book was released on 1990 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: A promising alternative to in situ methods such as wave buoys for measuring ocean wave spectra is HF ground wave radar. This paper describes an algorithm used to extract the nondirectional wave-height spectrum from the backscatter return of a stationary ship- or rig-mounted radar employing an omnidirectional antenna for both transmission and reception. To test the effectiveness of the algorithm, its estimates are compared to those of a WAVE-TRACK buoy using data collected onboard CFAV Quest during 1988.
Book Synopsis Direction and Frequency Resolution in HF Radar Directional Wave Spectra Measurements by : Lucy Rhiannon Wyatt
Download or read book Direction and Frequency Resolution in HF Radar Directional Wave Spectra Measurements written by Lucy Rhiannon Wyatt and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Aircraft and Satellite Measurement of Ocean Wave Directional Spectra Using Scanning-Beam Microwave Radars by : Frederick C. Jackson
Download or read book Aircraft and Satellite Measurement of Ocean Wave Directional Spectra Using Scanning-Beam Microwave Radars written by Frederick C. Jackson and published by . This book was released on 1982 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: A microwave radar technique for remotely measuring the vector wave-number spectrum of the ocean surface is described. The technique, which employs short-pulse, noncoherent radars in a conical scan mode near vertical incidence, is shown to be suitable for both aircraft and satellite application. The technique has been validated at 10 km aircraft altitude, where we have found excellent agreement between buoy and radar-inferred absolute wave-height spectra. (Author).
