scholarly journals Exploration and Validation of Wave-Height Measurement Using Multifrequency HF Radar

2013 ◽  
Vol 30 (9) ◽  
pp. 2189-2202 ◽  
Author(s):  
Zhao Chen ◽  
Chen Zezong ◽  
Jiang Yanni ◽  
Fan Lingang ◽  
Zeng Gengfei
Keyword(s):  
Wave Height ◽  
Radar System ◽  
Hf Radar ◽  
Least Mean Square ◽  
Fusion Algorithm ◽  
Height Measurement ◽  
Height Estimation ◽  
Data Process ◽  
Wide Range ◽  
Radar Wave

Abstract For operations across a wide range of oceanographic conditions, a radar system able to operate at more than one frequency is theoretically and experimentally recommended for robust wave measurement in recent years. To obtain more sea-state information by HF radar, a multifrequency HF (MHF) radar system, which can simultaneously operate at four frequencies at most in the band of 7.5–25 MHz, was developed by the Radio Wave Propagation Laboratory of Wuhan University in 2007. This paper mostly focuses on detailing the data process method of MHF radar wave-height estimation. According to different bands of operating frequencies, a least-mean-square (LMS) linear fitting method is adopted to calibrate wave-height estimation formulation, which is introduced by Barrick to extract significant wave height from backscatter Doppler spectra. Both the wave-height measurements of the initial and modified methods are compared with wave buoy measurements. Afterward, a data fusion algorithm of multifrequency estimates based on relevant factors quantification is discussed step by step. Three comparisons between radar-derived and buoy-measured estimates are presented to illustrate the performance of the MHF radar wave-height measurement. The statistics of the MHF radar wave-height measurements are listed and analyzed. The results show that the wave-height measurements of the MHF radar are in reasonable agreement with the measurements of the wave buoy.

scholarly journals A Wave Measurements HF Radar Data Set in the Malta-Sicily Channel: Data Quality, Validation and Gap Filling

10.29007/wg8s ◽  
2018 ◽  
Author(s):  
Marco Picone ◽  
Arianna Orasi ◽  
Aldo Drago ◽  
Fulvio Capodici ◽  
Giuseppe Ciraolo ◽  
...  
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Missing Values ◽  
Hf Radar ◽  
Data Set ◽  
Significant Wave ◽  
Wave Data ◽  
Wave Measurements ◽  
Sicily Channel ◽  
Radar Wave

The CALYPSO HF radar network is a permanent and fully operational observing system currently composed of four CODAR HF stations. The system is providing real- time hourly maps of sea surface currents and wave data in the Malta-Sicily Channel since 2012. Significant wave height derived from the HF radar wave measurements are confirmed to be a reliable source of wave information even in case of extreme events. However, it is noticed that the HF radar wave data are subject to differing interfering noise in the signal from unknown sources that may be competing with transmissions in the same frequency band. These interferences lead to frequent gaps and/or outliers that affect the continuity and reliability of the data set. The aim of this work is to estimate missing values and to detect possible outliers building and fitting a Markov chain mixture model on the significant wave height data collected at the four stations. It is verified that the proposed procedure is sufficiently robust since the model estimates succeed to classify radar observations with a high percentage of missing data and to equally highlight spikes and outliers.

scholarly journals A New Method of Wave Mapping with HF Radar

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Lijie Jin ◽  
Biyang Wen ◽  
Hao Zhou
Keyword(s):  
Wave Height ◽  
Second Harmonic ◽  
Mapping Method ◽  
Hf Radar ◽  
Great Success ◽  
Broad Beam ◽  
Wave Measurements ◽  
Wave Inversion ◽  
Local Wave ◽  
Radar Wave

Study of wave height inversion with High-Frequency Surface Wave Radars (HFSWRs) has been going on for more than 40 years. Various wave inversion methods have been proposed, and HFSWRs have achieved great success in local wave measurements. However, the method of wave mapping is still under development, especially for the broad-beam HF radars. Existing methods of wave mapping are based on narrow-beam radar with beamforming. This paper introduces a way of wave height inversion, using the ratio of the second-harmonic peak (SHP) to the Bragg peak (RSB). A new wave mapping method is proposed, which can be used in both narrow and broad-beam radars, according to the way of wave inversion based on the RSB. In addition, radar wave measurements at the buoy position are compared with thein situbuoy, which show a good agreement. At last, the results of wave mapping on the two-hour timescale are given.

scholarly journals Assessment of Significant Wave Height in the Taiwan Strait Measured by a Single HF Radar System

2019 ◽  
Vol 36 (7) ◽  
pp. 1419-1432 ◽  
Author(s):  
Linghui Cai ◽  
Shaoping Shang ◽  
Guomei Wei ◽  
Zhigang He ◽  
Yanshuang Xie ◽  
...  
Keyword(s):  
Wave Height ◽  
Significant Wave Height ◽  
Wave Model ◽  
Absolute Error ◽  
Taiwan Strait ◽  
Radar System ◽  
Hf Radar ◽  
Study Region ◽  
Significant Wave ◽  
Wave Measurements

AbstractDual high-frequency (HF) radar systems are often used to provide measurements of waves, winds, and currents. In this study, the accuracy of wave measurements using a single HF radar system (OS081H-A) was explored using datasets obtained during 5–27 January 2014 in the southwestern Taiwan Strait. We selected the study region as an area with >90% coverage (i.e., the range was <100 km). Qualitative and quantitative intercomparison of wave measurements (by the radar and five buoys) and wave model products [from the Simulating Wave Nearshore (SWAN) model] were conducted. Intercomparison of the modeled and in situ significant wave height Hs showed that the model-predicted Hs could be considered to be acceptable for use as “sea truth” to evaluate the radar-derived Hs, with mean bias from −0.45 to −0.16 m, mean absolute error (MAE) of 0.24–0.45 m, and root-mean-square error of 0.31–0.54 m. It was found that the MAE of radar-derived Hs was ≤ 1 m for 86% of the sector (except at the edge of sector) when the model-predicted Hs was ≥ 1.5 m. In particular, the MAE was less than 0.6 m for 63% of the sector, which was mainly distributed in the area with a bearing from −50° to +70° and a range of 20–70 km. The results are promising, but more work is needed. We employed a spatial distribution function for the MAE of the radar-derived Hs over the sample duration based on range, bearing, and mean radar-derived Hs.

Improving the uncertainty of ocean surface wind and wave parameters estimated by a single HF radar system

2020 ◽  
Author(s):  
Duy-Toan Dao ◽  
Hwa Chien ◽  
Pierre Flament
Keyword(s):  
Wave Height ◽  
Wind Field ◽  
Radar System ◽  
Hf Radar ◽  
Image Processing Technique ◽  
Watershed Segmentation ◽  
Order Component ◽  
Sea State ◽  
Wave Parameters

&lt;p&gt;A 16 Rx element linear array HF radar system (LERA III), working at 27.75 MHz and 300kHz in bandwidth, was installed at the north of Taichung harbor at the western coast of Taiwan in November 2018. This LERA system is low-cost, compact in size, easy to set-up, and maintain. The purpose of present studies is to implement algorithms for retrieving wave and wind fields and assess the system performance in terms of operational mode. For inter-comparison, the long-term in-situ wave data measured by an AWAC was adopted. Wind data were measured from a coastal wind gauge. The inter-comparisons between radar data and in-situ data were carried out on seasonal basis, including severe sea states during winter monsoon and passage of typhoon as well as calm seas during spring.&lt;/p&gt;&lt;p&gt;For the data processing, the Doppler-range spectrum for each azimuth direction was extracted by using the classical beam-forming technique and then provided as level 1 product for further analysis. Regarding the method for retrieving wave parameters, formulations directly derived from Barrick&amp;#8217;s assumption was implemented. In those formulas, wave parameters are calculated based on the ratio of the 2&lt;sup&gt;nd&lt;/sup&gt; order component multiplied by the coupling coefficient function to the 1&lt;sup&gt;st&lt;/sup&gt; order component in the Doppler spectrum. It means that no empirical constants were included. Initially, Wyatt&amp;#8217;s (1999, 2011) and Walsh &amp; Howell&amp;#8217;s (1993) methods were applied to determine the lower and higher bounds that separate the 1&lt;sup&gt;st&lt;/sup&gt; and 2&lt;sup&gt;nd&lt;/sup&gt; order component. For wind speed inversion, Dexter &amp; Theodorides&amp;#8217;s (1982) method was adopted. The Bragg wave direction was used as a proxy to the direction of the wind field.&lt;/p&gt;&lt;p&gt;It is found that when using Wyatt&amp;#8217;s (1999, 2011) method, the wave height and period results often lead to bias estimations for severe sea-state, and with the presence of highly variable surface current. In order to improve the accuracy, adaptive methods for the identification of spectra component areas is crucial. In this study, an alternative method is proposed. This method is developed based on the concept proposed by Kirincich (2017), which includes the pretreatment of Doppler-rang spectrums, marker-controlled watershed segmentation, and an image processing technique. In this research, we will demonstrate the advantages of using the new method for wave and wind field retrieval. From comparative studies, the error indexes based on the sea truth data are discussed. It is found that the accuracy would be improved using the proposed method, especially for the cases of varying current fields, severe sea state, and noisy radio background.&lt;/p&gt;&lt;p&gt;Key words: high-frequency surface wave radar; phased array antennas; significant wave height, wave period, marker-controlled watershed segmentation (MCWS) techniques.&lt;/p&gt;

scholarly journals A Consistent Track-to-Track Fusion Method Based on Copula Theory

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Kelin Lu ◽  
K. C. Chang ◽  
Rui Zhou
Keyword(s):  
Probability Distributions ◽  
A Priori ◽  
Joint Probability ◽  
Network Connectivity ◽  
Consistent Estimate ◽  
Fusion Algorithm ◽  
Copula Theory ◽  
Wide Range ◽  
Primary Advantage ◽  
Joint Probability Distributions

This paper addresses the problem of distributed fusion when the conditional independence assumptions on sensor measurements or local estimates are not met. A new data fusion algorithm called Copula fusion is presented. The proposed method is grounded on Copula statistical modeling and Bayesian analysis. The primary advantage of the Copula-based methodology is that it could reveal the unknown correlation that allows one to build joint probability distributions with potentially arbitrary underlying marginals and a desired intermodal dependence. The proposed fusion algorithm requires no a priori knowledge of communications patterns or network connectivity. The simulation results show that the Copula fusion brings a consistent estimate for a wide range of process noises.

Distribution of Wave Impact Forces From Breaking and Non-Breaking Waves

2009 ◽  
Author(s):  
Anne M. Fullerton ◽  
Thomas C. Fu ◽  
Edward S. Ammeen
Keyword(s):  
Free Surface ◽  
Wave Height ◽  
Breaking Waves ◽  
Qualitative Assessment ◽  
Total Force ◽  
Impact Loads ◽  
Wave Impact ◽  
Data Set ◽  
Wave Characteristics ◽  
Wide Range

Impact loads from waves on vessels and coastal structures are highly complex and may involve wave breaking, making these changes difficult to estimate numerically or empirically. Results from previous experiments have shown a wide range of forces and pressures measured from breaking and non-breaking waves, with no clear trend between wave characteristics and the localized forces and pressures that they generate. In 2008, a canonical breaking wave impact data set was obtained at the Naval Surface Warfare Center, Carderock Division, by measuring the distribution of impact pressures of incident non-breaking and breaking waves on one face of a cube. The effects of wave height, wavelength, face orientation, face angle, and submergence depth were investigated. A limited number of runs were made at low forward speeds, ranging from about 0.5 to 2 knots (0.26 to 1.03 m/s). The measurement cube was outfitted with a removable instrumented plate measuring 1 ft2 (0.09 m2), and the wave heights tested ranged from 8–14 inches (20.3 to 35.6 cm). The instrumented plate had 9 slam panels of varying sizes made from polyvinyl chloride (PVC) and 11 pressure gages; this data was collected at 5 kHz to capture the dynamic response of the gages and panels and fully resolve the shapes of the impacts. A Kistler gage was used to measure the total force averaged over the cube face. A bottom mounted acoustic Doppler current profiler (ADCP) was used to obtain measurements of velocity through the water column to provide incoming velocity boundary conditions. A Light Detecting and Ranging (LiDAR) system was also used above the basin to obtain a surface mapping of the free surface over a distance of approximately 15 feet (4.6 m). Additional point measurements of the free surface were made using acoustic distance sensors. Standard and high-speed video cameras were used to capture a qualitative assessment of the impacts. Impact loads on the plate tend to increase with wave height, as well as with plate inclination toward incoming waves. Further trends of the pressures and forces with wave characteristics, cube orientation, draft and face angle are investigated and presented in this paper, and are also compared with previous test results.

scholarly journals A novel dual-channel HF radar system for ionospheric sounding

2018 ◽  
Vol 7 (1) ◽  
pp. 25-30
Author(s):  
Lei Qiao ◽  
Liang Huang ◽  
Xiao Cui
Keyword(s):  
Radar System ◽  
Hf Radar ◽  
Dual Channel ◽  
Ionospheric Sounding

scholarly journals A Novel Target-Height Estimation Approach Using Radar-Wave Multipath Propagation for Automotive Applications

2017 ◽  
Vol 15 ◽  
pp. 61-67
Author(s):  
Amir Laribi ◽  
Markus Hahn ◽  
Jürgen Dickmann ◽  
Christian Waldschmidt
Keyword(s):  
Continuous Wave ◽  
Multipath Propagation ◽  
Estimation Error ◽  
Propagation Model ◽  
Target Range ◽  
Target Height ◽  
Height Estimation ◽  
Range Resolution ◽  
Novel Target ◽  
Radar Wave

Abstract. This paper introduces a novel target height estimation approach using a Frequency Modulation Continuous Wave (FMCW) automotive radar. The presented algorithm takes advantage of radar wave multipath propagation to measure the height of objects in the vehicle surroundings. A multipath propagation model is presented first, then a target height is formulated using geometry, based on the presented propagation model. It is then shown from Sensor-Target geometry that height estimation of targets is highly dependent on the radar range resolution, target range and target height. The high resolution algorithm RELAX is discussed and applied to collected raw data to enhance the radar range resolution capability. This enables a more accurate height estimation especially for low targets. Finally, the results of a measurement campaign using corner reflectors at different heights are discussed to show that target heights can be very accurately resolved by the proposed algorithm and that for low targets an average mean height estimation error of 0.03 m has been achieved by the proposed height finding algorithm.

Overcoming Challenges of Mechanical Lifting Capabilities on Offshore Installation by Utilizing Coiled Tubing Boat Spooling Technique

2021 ◽  
Author(s):  
Stefan Dinger ◽  
Andrei Casali ◽  
Frank Lind ◽  
Azwan Hadi Keong ◽  
Johnny Bårdsen ◽  
...  
Keyword(s):  
Wind Speed ◽  
Real Time ◽  
Wave Height ◽  
Careful Study ◽  
Sea State ◽  
M Wave ◽  
Coiled Tubing ◽  
Wide Range ◽  
Downhole Measurements ◽  
Outside Diameter

Abstract Coiled tubing (CT) operations in the Norwegian continental shelf (NCS) often require a long and large-outside-diameter pipe due to big diameter completions, deep wells, and the need for high annular velocity during fluid circulation. However, getting the CT string onboard becomes a challenge when the crane lifting limit is 35 t, and using a standalone crane barge increases the cost of the operation. The alternative is spooling the CT from a vessel to the platform. Boat spooling is done by placing the CT string on a floating vessel with dynamic positioning while the standard CT injector head is secured at the edge of the platform to pull the pipe from the vessel to an empty CT reel on the platform. The boat is equipped with a CT guide; special tension clamps; and an emergency disconnect system, which consists of a standard CT shear-seal blowout preventer. The technique requires careful study of the platform structure for placement of the injector head support frame, metocean data of the field, and equipment placement on the vessel and platform. The boat spooling operation of a 7,700-m long, 58.7-t, 2.375-in.-outside-diameter CT string was successfully executed for a platform at 70-m height from mean sea level. The total operating time from hooking up the vessel to successfully spooling the string only took 12 hours. Historically for the region, the method has been attempted in sea state of up to 4-m wave height and 16 knots maximum wind speed. For this operation, the spooling was carried out during an average sea state of 2-m wave height and 15-knot wind speed. The continuous CT string allows a telemetry cable to be installed inside the pipe after the CT is spooled onto the platform reel, enabling real-time downhole measurements during the intervention. Such installation is not possible or presents high risk if the CT string is taken onboard by splicing two sections of pipe together with a spoolable connector or butt welding. From a cost perspective, the boat-spooling operation had up to 80% direct cost saving for the operator when compared to other methods of lifting a single CT string onboard, such as using a motion-compensated barge crane. The planning for the boat spooling included several essential contingency plans. Performing a CT boat spooling operation in a complex environment is possible and opens new opportunities to use longer and heavier CT strings, with lower mobilization costs. Such strings enable more advanced and efficient interventions, with the option of using real-time CT downhole measurements during the execution of a wide range of production startup work. This, in turn, is critical to support the drilling of more extended reach wells, which allow access to untapped reservoirs.

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