Laboratory Comparison of Directional Wave Measurement Systems and Analysis Techniques

1995 ◽  
Author(s):  
Michel Benoit ◽  
Charles Teisson
Keyword(s):  
Measurement Systems ◽  
Analysis Techniques ◽  
Wave Measurement ◽  
Directional Wave

scholarly journals Quantifying wave measurement differences in historical and present wave buoy systems

2021 ◽  
Author(s):  
Robert Edward Jensen ◽  
Val Swail ◽  
Richard Harry Bouchard
Keyword(s):  
Complex Nature ◽  
Frequency Spectra ◽  
Measurement Systems ◽  
Wave Measurements ◽  
Directional Sensors ◽  
Wave Measurement ◽  
Western Us ◽  
Directional Wave ◽  
Wind Sea ◽  
Wave Properties

AbstractAn intra-measurement evaluation was undertaken, deploying a NOMAD buoy equipped with three National Data Buoy Center and two Environment and Climate Change Canada-AXYS sensor/payload packages off Monterey, California; a Datawell Directional Waverider buoy was deployed within 19 km of the NOMAD site. The six independent wave measurement systems reported hourly estimates of the frequency spectra, and when applicable, the four Fourier directional components. The integral wave parameters showed general agreement among the five sensors compared to the neighboring Datawell Directional Waverider, with the Inclinometer and the Watchman performing similarly to the more sophisticated 3DMG, HIPPY, and Triaxys sensor packages. As the Hm0 increased, all but the Inclinometer were biased low; however, even the Watchman reported reasonable wave measurements up to about 6–7 m, after which the Hm0 becomes negatively biased up to about a meter, comparable to previous studies. The parabolic fit peak spectral wave period, Tpp, results showed a large scatter, resulting from the complex nature of multiple swell wave systems compounded by local wind-sea development, exacerbated by a variable that can be considered as temporally unstable. The three directional sensors demonstrated that NOMAD buoys are capable of measuring directional wave properties along the western US coast, with biases of about 6 to 9 deg, and rms errors of approximately 30 deg. Frequency spectral evaluations found similarities in the shape, but a significant under estimation in the high frequency range. The results from slope analyses also revealed a positive bias in the rear face of the spectra, and a lack of invariance in frequency as suggested by theory.

scholarly journals Smoothing warships movements based on wavelets

2013 ◽  
Vol 6 (12) ◽  
pp. 51
Author(s):  
J.M. Riola ◽  
J.M. Girón ◽  
J.J. Díaz
Keyword(s):  
Weather Conditions ◽  
Point Of View ◽  
Ship Motions ◽  
Main Question ◽  
Measurement Systems ◽  
Quiescent Period ◽  
Wave Measurement ◽  
Key Issues ◽  
The Waves ◽  
Initial Measurement

In seakeeping terminology, the Quiescent Period is known as the period of calm in rough waters to allow the ship to perform operations such as landing aircrafts and unmanned aerial vehicles (UAVs), aswell as the entry of landing crafts in the basin. Quiescence refers to the interval of time where all ship motions are within acceptable limits to perform a desired activity. Among the key issues for Quiescent Period Prediction is to be able to measure waves from a suitable distance and predict ship motions in response to waves encountered; both aspects are crucial and must be taken into account. Many of the opearations performed at sea are carried under severe weather conditions, as a result of this situation there is a need to determine this called “window of opportunity” that allows carrying them out. The paper aims to explain from the point of view of Quiescent Period Prediction, the most promising wave measurement systems, which are currently based on radar, but the main question is that if we want predictions a few seconds ahead, it will be appropriate to measure waves at a distance of some hundreds of meters, describing the new mathematical model based on wavelets in determining the spread of the waves from their initial measurement until they reach the vessel.

Frequency and Time Signal Analysis in Source Identification of Vibration and Noise in Cylindrical Cam Mechanisms

1997 ◽  
Author(s):  
Song Lin Ge ◽  
Giovanni Nerli ◽  
Marco Pierini
Keyword(s):  
Research Work ◽  
Time Signal ◽  
Noise Levels ◽  
Noise And Vibration ◽  
Measurement Systems ◽  
Analysis Techniques ◽  
Cam Mechanism ◽  
Frequency Domains ◽  
System Characteristics ◽  
Accelerometer Measurement

Abstract It is vitally important to identify sources from which unwanted noise and vibration are emitted before further research work can commence on the design optimization of the cylindrical cam mechanism. Acoustic microphone and vibration accelerometer measurement systems were used to analyze the system characteristics in both the time and frequency domains. We have succeeded in identifying the sources of noise and vibration and distinguishing the signals between the regions of the groove junctions and the groove inversions in terms of the relative values of their instantaneous powers. Some of the problems encountered were impossible to resolve using only frequency analysis techniques due to the characteristics of the rectilinear reciprocating motions of the cam mechanism follower. The results obtained from the cam analyzed show that the structure of the groove inversion has a greater influence on the noise levels emitted from the mechanism than the structure of the groove junction. The emitted noise level from the former is generally twice that emitted from the latter.

NOAA’s recent field testing of current and wave measurement systems – part ii

2015 ◽  
Author(s):  
William Douglas Wilson ◽  
Robert Heitsenrether ◽  
Grace Gray ◽  
Nathan Holcomb ◽  
Chung-Chu Teng
Keyword(s):  
Field Testing ◽  
Measurement Systems ◽  
Wave Measurement

scholarly journals Research on the Algorithm Model for Measuring Ocean Waves Based on Satellite GPS Signals in China

Sensors ◽  
2019 ◽  
Vol 19 (3) ◽  
pp. 541 ◽  
Author(s):  
Zhanhui Qi ◽  
Shaowu Li ◽  
Mingbing Li ◽  
Chaoqun Dang ◽  
Dongbo Sun ◽  
...  
Keyword(s):  
Wave Spectrum ◽  
Ocean Wave ◽  
Acquisition Time ◽  
Measurement Technology ◽  
Movement Velocity ◽  
Wave Parameters ◽  
Wave Measurement ◽  
Improvement Measures ◽  
Directional Wave ◽  
Gravity Acceleration

In recent years, the GPS wave buoy has been developed for in situ wave monitoring based on satellite GPS signals. Many research works have been completed on the GPS-based wave measurement technology and great progress has been achieved. The basic principle of the GPS wave buoy is to calculate the movement velocity of the buoy using the Doppler frequency shift of satellite GPS signals, and then to calculate the wave parameters from the movement velocity according to ocean wave theory. The shortage of the GPS wave buoy is the occasional occurrence of some unusual values in the movement velocity. This is mainly due to the fact that the GPS antenna is occasionally covered by sea water and cannot normally receive high-quality satellite GPS signals. The traditional solution is to remove these unusual movement velocity values from the records, which requires furthering extend the acquisition time of satellite GPS signals to ensure there is a large enough quantity of effective movement velocity values. Based on the traditional GPS wave measurement technology, this paper presents the algorithmic flow and proposes two improvement measures. On the one hand, the neural network algorithm is used to correct the unusual movement velocity data so that extending the acquisition time of satellite GPS signals is not necessary and battery power is saved. On the other hand, the Gaussian low-pass filter is used to correct the raw directional wave spectrum, which can further eliminate the influence of noise spectrum energy and improve the measurement accuracy. The on-site sea test of the SBF7-1A GPS wave buoy, developed by the National Ocean Technology Center in China, and the gravity-acceleration-type DWR-MKIII Waverider buoy are highlighted in this article. The wave data acquired by the two buoys are analyzed and processed. It can be seen from the processed results that the ocean wave parameters from the two kinds of wave buoys, such as wave height, wave period, wave direction, wave frequency spectrum, and directional wave spectrum, are in good consistency, indicating that the SBF7-1A GPS wave buoy is comparable to the traditional gravity-acceleration-type wave buoy in terms of its accuracy. Therefore, the feasibility and validity of the two improvement measures proposed in this paper are confirmed.

Assessing the Quality of Directional Wave Measurement by a Differential GPS Buoy

2001 ◽  
Author(s):  
M. Rossouw ◽  
A. van Tonder ◽  
U. von St Ange ◽  
L. Coetzee ◽  
J. Davies
Keyword(s):  
Differential Gps ◽  
Wave Measurement ◽  
Gps Buoy ◽  
Directional Wave

Verification of Wave Measurement Systems

2013 ◽  
Vol 47 (5) ◽  
pp. 104-116 ◽  
Author(s):  
Mark E. Luther ◽  
Guy Meadows ◽  
Earle Buckley ◽  
Sherryl A. Gilbert ◽  
Heidi Purcell ◽  
...  
Keyword(s):  
Shallow Water ◽  
Water Wave ◽  
New Technologies ◽  
Reference Method ◽  
Army Corps ◽  
Intermediate Water ◽  
Measurement Systems ◽  
Test And Evaluation ◽  
Wave Measurement ◽  
Wide Range

AbstractGiven the societal importance of reliable and accurate ocean observations, the wave monitoring community (including academic researchers, agency scientists, resource managers, and representatives from wave instrument manufacturers) came together to develop a set of protocols for the test and evaluation of wave measurement systems in support of the 2009 National Operational Wave Observation Plan. These protocols are focused on a wide range of wave measurement instruments and their respective performance in successfully recovering the “First-5” Fourier components of the incident wave field. Performance is determined by comparing each system’s output with a verifiable reference method over a predetermined range of wave frequencies. It is recommended that permanent wave test facilities are created on the West Coast (Monterey Bay, CA—deep water) and the East Coast (Duck, NC—shallow water) for continued evaluations of existing and new technologies. It was recognized that no absolute standard exists for the determination of the “First-5” across all spatial domains. Therefore, it was agreed that the Directional Waverider DWR-MkIII system was the best available reference/standard for the deep and intermediate water wave evaluations as verified by the laser array (LASAR) at the ConocoPhillips Ekofisk offshore platform complex in the North Sea. The long linear array at the U.S. Army Corps of Engineers’ Field Research Facility could be used as the standard for shallow water wave evaluations. Finally, given the significance of wave measurements, an appropriate level of quality assurance and quality control procedures must be included as part of any test and evaluation effort. The details of the proposed protocols for the verification of wave measurement systems are described.

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