Streamer compass validation and verification

Geophysics ◽  
1993 ◽  
Vol 58 (4) ◽  
pp. 589-592
Author(s):  
Ian N. Court
Keyword(s):  
Least Squares ◽  
Seismic Data ◽  
Additional Data ◽  
Integration Method ◽  
Validation And Verification ◽  
Position Information ◽  
Spatial Gradients ◽  
Fitting Algorithm ◽  
Undetermined Constant

During the acquisition of seismic data in a marine environment, the positions of the hydrophone groups are derived from data obtained using compass units deployed at intervals along the length of a streamer. Interpretation of the compass data to derive the streamer position has always proved difficult. The data is a set of measurements of spatial gradients at known distances along the streamer. The integration method used to derive the streamer shape requires additional data to resolve the undetermined constant. Thus the derived positions of the hydrophone groups have a translational indeterminacy. The compass measurements are independent and all measured azimuths can he expected to have similar error estimates. However streamer shapes, derived using a least‐squares polynomial fitting algorithm are critically dependent on the accuracy of data obtained from the first and last units. These features have lead to innovative schemes to position the two ends of the streamers. Lasers, acoustics, and radio positioning, have all been used to locate accessible points closest to the streamer ends viz the towpoints and the tailbuoy. While this additional data has improved the quality of streamer positioning, these methods still leave the compasses as the only means of generating position information in the region where the hydrophone groups are actually situated.

Migration using sea surface-related multiples: Challenges and opportunities

Geophysics ◽  
2021 ◽  
pp. 1-42
Author(s):  
Shaoping Lu
Keyword(s):  
Data Acquisition ◽  
Least Squares ◽  
Seismic Data ◽  
Sea Surface ◽  
Seismic Exploration ◽  
Algorithm Development ◽  
Challenges And Opportunities ◽  
Seismic Data Acquisition ◽  
Marine Seismic

In marine seismic exploration, it has been well known that sea surface-related multiples can be treated as signals to image the subsurface and provide extended illumination. Previous studies on imaging of multiples have been mainly focusing on its algorithm development and implementation. This paper serves as a tutorial where we systematically investigate the fundamental challenges in the process of imaging of multiples. We first examine the impacts of marine seismic data acquisition parameters: such as offset, trace spacing and streamer towing direction, which are all key elements that control the quality of the images of multiples, and illustrate that 3D towed streamer and OBS surveys are preferable acquisition geometries to apply imaging of multiples. In addition, we investigate the challenges in jointly imaging primaries and multiples and the crosstalk problem in the process, and demonstrate that a Least-Squares inversion based algorithm is effective to address these issues. With the proper handling of all those challenges, imaging of multiples can help to mitigate shallow acquisition footprints, improve salt boundary illumination and enhance the imaging resolution, which allow the identification of drilling hazards and reduction in drilling risks. To apply imaging of multiples in practice, the objective is not to replace but to augment imaging of primaries by providing extra illumination.

scholarly journals Research on the Manufacturing Quality of Co-Cured Hat-Stiffened Composite Structure

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2747
Author(s):  
Xiangwen Ju ◽  
Jun Xiao ◽  
Dongli Wang ◽  
Cong Zhao ◽  
Xianfeng Wang
Keyword(s):  
Composite Structures ◽  
Sound Pressure ◽  
Integration Method ◽  
Complex Geometry ◽  
Sound Field ◽  
Thickness Measurement ◽  
Curing Process ◽  
The Finite Element Method ◽  
Manufacturing Quality

The stringer-stiffened structure is widely used due to its excellent mechanical properties. Improving the manufacturing quality of stringer-stiffened structure which have complex geometry is important to ensure the bearing capacity of aviation components. Herein, composite hat-stiffened composite structures were manufactured by different filling forms and bladders with various properties, the deformation of silicone rubber bladder in co-curing process was studied by using the finite element method. The thickness measurement at different positions of the hat-stiffened structure was performed to determine the best filling form and bladder property. Moreover, in view of the detection difficulties in R-zone of stringer, numerical simulation was performed to get the sound pressure and impulse response of at the R-zone of stringer by Rayleigh integration method, and an effective equipment which could stably detect the manufacturing quality of R-zone was designed to verify the correctness of sound field simulation and realize the detection of stringer. With the optimum filling form and bladder properties, hat-stiffened composites can be manufactured integrally with improved surface quality and geometric accuracy, based on co-curing process.

scholarly journals How Good Is the STW Sensor? An Account from a Larger Shipping Company

2021 ◽  
Vol 9 (5) ◽  
pp. 465
Author(s):  
Angelos Ikonomakis ◽  
Ulrik Dam Nielsen ◽  
Klaus Kähler Holst ◽  
Jesper Dietz ◽  
Roberto Galeazzi
Keyword(s):  
High Frequency ◽  
Additional Data ◽  
Empirical Method ◽  
Influential Factor ◽  
Sensor Data ◽  
Sea State ◽  
Shipping Company ◽  
Frequency Sensor ◽  
Semi Empirical

This paper examines the statistical properties and the quality of the speed through water (STW) measurement based on data extracted from almost 200 container ships of Maersk Line’s fleet for 3 years of operation. The analysis uses high-frequency sensor data along with additional data sources derived from external providers. The interest of the study has its background in the accuracy of STW measurement as the most important parameter in the assessment of a ship’s performance analysis. The paper contains a thorough analysis of the measurements assumed to be related with the STW error, along with a descriptive decomposition of the main variables by sea region including sea state, vessel class, vessel IMO number and manufacturer of the speed-log installed in each ship. The paper suggests a semi-empirical method using a threshold to identify potential error in a ship’s STW measurement. The study revealed that the sea region is the most influential factor for the STW accuracy and that 26% of the ships of the dataset’s fleet warrant further investigation.

Regularization and datuming of seismic data by weighted, damped least squares

Geophysics ◽  
2006 ◽  
Vol 71 (5) ◽  
pp. U67-U76 ◽  
Author(s):  
Robert J. Ferguson
Keyword(s):  
Least Squares ◽  
Seismic Data ◽  
Synthetic Data ◽  
Real Data ◽  
Structural Data ◽  
Irregular Sampling ◽  
Data Set ◽  
Near Surface ◽  
Damped Least Squares ◽  
Wavefield Extrapolation

The possibility of improving regularization/datuming of seismic data is investigated by treating wavefield extrapolation as an inversion problem. Weighted, damped least squares is then used to produce the regularized/datumed wavefield. Regularization/datuming is extremely costly because of computing the Hessian, so an efficient approximation is introduced. Approximation is achieved by computing a limited number of diagonals in the operators involved. Real and synthetic data examples demonstrate the utility of this approach. For synthetic data, regularization/datuming is demonstrated for large extrapolation distances using a highly irregular recording array. Without approximation, regularization/datuming returns a regularized wavefield with reduced operator artifacts when compared to a nonregularizing method such as generalized phase shift plus interpolation (PSPI). Approximate regularization/datuming returns a regularized wavefield for approximately two orders of magnitude less in cost; but it is dip limited, though in a controllable way, compared to the full method. The Foothills structural data set, a freely available data set from the Rocky Mountains of Canada, demonstrates application to real data. The data have highly irregular sampling along the shot coordinate, and they suffer from significant near-surface effects. Approximate regularization/datuming returns common receiver data that are superior in appearance compared to conventional datuming.

Variable-Frequency Prony Method in the Analysis of Electrical Power Quality

2012 ◽  
Vol 19 (1) ◽  
pp. 39-48 ◽  
Author(s):  
Jarosław Zygarlicki ◽  
Janusz Mroczka
Keyword(s):  
Least Squares ◽  
Power Quality ◽  
Electrical Power ◽  
Electric Energy ◽  
Variable Frequency ◽  
Prony Method ◽  
Analysis Window ◽  
Proposed Modification ◽  
Selection Of

Variable-Frequency Prony Method in the Analysis of Electrical Power QualityThe article presents a new modification of the the least squares Prony method. The so-called variable-frequency Prony method can be a useful tool for estimating parameters of sinusoidal components, which, in the analyzed signal, are characterized by time-dependent frequencies. The authors propose use of the presented method for testing the quality of electric energy. It allows observation of phenomena which, when using traditional methods, are averaged in the analysis window. The proposed modification of least squares Prony method is based on introduction and specific selection of a frequency matrix. This matrix represents frequencies of estimated components and their variability in time.

Plane-wave least-squares reverse time migration with a preconditioned stochastic conjugate gradient method

Geophysics ◽  
2018 ◽  
Vol 83 (1) ◽  
pp. S33-S46 ◽  
Author(s):  
Chuang Li ◽  
Jianping Huang ◽  
Zhenchun Li ◽  
Rongrong Wang
Keyword(s):  
Plane Wave ◽  
Least Squares ◽  
Conjugate Gradient ◽  
Sampling Method ◽  
Singular Spectrum Analysis ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Numerical Tests ◽  
Time Migration

This study derives a preconditioned stochastic conjugate gradient (CG) method that combines stochastic optimization with singular spectrum analysis (SSA) denoising to improve the efficiency and image quality of plane-wave least-squares reverse time migration (PLSRTM). This method reduces the computational costs of PLSRTM by applying a controlled group-sampling method to a sufficiently large number of plane-wave sections and accelerates the convergence using a hybrid of stochastic descent (SD) iteration and CG iteration. However, the group sampling also produces aliasing artifacts in the migration results. We use SSA denoising as a preconditioner to remove the artifacts. Moreover, we implement the preconditioning on the take-off angle-domain common-image gathers (CIGs) for better results. We conduct numerical tests using the Marmousi model and Sigsbee2A salt model and compare the results of this method with those of the SD method and the CG method. The results demonstrate that our method efficiently eliminates the artifacts and produces high-quality images and CIGs.

scholarly journals GEOMETRIC ASPECTS EVALUATION OF GNSS CONTROL NETWORK FOR DEFORMATION MONITORING IN THE JATIGEDE DAM REGION

2019 ◽  
Vol 15 (2) ◽  
pp. 167
Author(s):  
Made Ditha Ary Sanjaya ◽  
T. Aris Sunantyo ◽  
Nurrohmat Widjajanti
Keyword(s):  
Least Squares ◽  
Deformation Monitoring ◽  
Network Configuration ◽  
Control Networks ◽  
Quality Of Control ◽  
Least Squares Adjustment ◽  
Standard Deviations ◽  
Dam Deformation ◽  
Gnss Networks

Many factors led to dam construction failure so that deformation monitoring activities is needed in the area of the dam. Deformation monitoring is performed in order to detect a displacement at the control points of the dam. Jatigede Dam deformation monitoring system has been installed and started to operate, but there has been no evaluation of the geometry quality of control networks treated with IGS points for GNSS networks processing. Therefore, this study aims to evaluate the geometric quality of GNSS control networks on deformation monitoring of Jatigede Dam area. This research data includes the GNSS measurements of five CORS Jatigede Dam stations (R01, GG01, GCP04, GCP06, and GCP08) at doy 233 with network configuration scenarios of 12 IGS points on two quadrants (jat1), three quadrants (jat2), and four quadrants (jat3 and jat4). GNSS networks processing was done by GAMIT to obtain baseline vectors, followed by network processing usingparameter method of least squares adjustment. Networks processing with least squares adjustment aims to determine the most optimal  by precision and reliability criterion. Results of this study indicate that network configuration with 12 IGS stations in the two quadrants provides the most accurate coordinates of CORS dam stations. Standard deviations value of CORS station given by jat1 configuration are in the range of 2.7 up to 4.1 cm in X-Z components, whereas standard deviations in the Y component are in the range 5.8 up to 6.9 cm. An optimization assessment based on network strength, precision, and reliability factors shows optimum configuration by jat1.

Seismic anisotropy

Geophysics ◽  
2001 ◽  
Vol 66 (1) ◽  
pp. 40-41 ◽  
Author(s):  
Leon Thomsen
Keyword(s):  
Future Development ◽  
Seismic Data ◽  
Seismic Anisotropy ◽  
Practical Interest ◽  
Exploration And Exploitation ◽  
Principal Reason ◽  
The Past ◽  
High Level ◽  
Effective Use

The topic of seismic anisotropy in exploration and exploitation has seen a great deal of progress in the past decade‐and‐a‐half. The principal reason for this is the increased (and increasing) quality of seismic data, of the processing done to it, and of the interpretation expected from it. No longer an academic subject of little practical interest, it is now often viewed as one of the crucial factors which, if not taken into account, severely hampers our effective use of the data. The following brief overview is not intended to be exhaustive, since any such attempt would surely be incomplete. However, it does provide a high‐level survey of the advances seen (at the end of this period) to be important by one who was closely involved, and it directly extrapolates this history to predict the future development of the topic.

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