scholarly journals A semi-automatic approach to identify first arrival time: the Cross-Correlation Technique

2015 ◽  
Vol 18 (2) ◽  
pp. 107-113 ◽  
Author(s):  
Mustafa Senkaya ◽  
Hakan Karslı
Keyword(s):  
Cross Correlation ◽  
Seismic Refraction ◽  
Correlation Technique ◽  
Arrival Times ◽  
Refraction Tomography ◽  
First Arrival ◽  
The Cross ◽  
Seismic Refraction Data ◽  
Cross Correlation Technique ◽  
Refraction Data

<p class="MsoNormal" style="line-height: 200%;">The high-quality interpretation of seismic refraction data depends on the accurate and reliable identification of the first arrival times. First arrivals can be identified on a graphic or image by conventional picking, but this process depends on external factors, such as the scale and quality of the imaging data, amplitude ratio, sensitivity of the picking cursor and user experience. Under these considerations, identifying first arrivals in noisy data becomes more complex and unstable. In this study, the Cross-Correlation Technique (CCT), which is widely used in the process of analyzing reflection data, has been used to pick the first arrival times in noisy or noiseless seismic refraction data by a semi-automatic process. The CCT has reduced the dependence on user and decreased incorrect picking caused by environmental noise, displaying characteristics and scaling factors. The CCT has been tested with synthetic models with different noise contents and various field data. The Chi-square error criterion was used to assess the performance of the pickings. In addition, effects of small-time differences between the conventional picking process and the CCT have been demonstrated on a refraction tomography velocity section. Therefore, we believe that our proposed method is a useful contribution to the existing methods of first arrival picking.</p><p class="MsoNormal" style="line-height: 200%;"> </p><p class="MsoNormal" style="line-height: 200%;"><strong>Resumen</strong></p><p class="MsoNormal" style="line-height: 200%;">La buena interpretación de datos estadísticos de refracción sísmica depende de la identificación acertada y confiable de los tiempos de llegada. Los primeros tiempos de llegada se pueden identificar en un gráfico o imagen por picado convencional, pero este proceso depende de factores externos como la escala y la calidad de información de la imagen, el índice de amplitud, la sensibilidad del cursor de recolección y la experiencia del usuario. Bajo estas consideraciones, la identificación de los tiempos de llegada bajo información ruidosa se vuelve más compleja e inestable. En este estudio, la técnica de Correlación Cruzada (CCT, en inglés), que es ampliamente trabajada en el proceso de análisis de datos de reflexión, se utilizó para seleccionar los primeros tiempos de llegada en información sísmica ruidosa o no ruidosa con un proceso semiautomático. La CCT redujo la dependencia en el usuario y bajó el nivel de selección incorrecta causada por el ruido ambiental al desplegar características y factores de escala. La CCT se ha probado en modelos sintéticos con diferentes contenidos de ruidos y diversa información de campo. El error de la norma Chi-cuadrado se utilizó para evaluar el desempeño de las selecciones. En adición, los efectos de las pequeñas diferencias de tiempo entre el proceso convencional de selección y la CCT se han demostrado en una tomografía reflexiva de velocidad. Además, se estima que el método propuesto es una contribución útil a los métodos existentes de la recolección de los primeros tiempos de llegada.</p>

Pipeline system identification through cross-correlation analysis

2002 ◽  
Vol 216 (3) ◽  
pp. 133-142 ◽  
Author(s):  
S B M Beck ◽  
N J Williamson ◽  
N D Sims ◽  
R Stanway
Keyword(s):  
Correlation Analysis ◽  
Cross Correlation ◽  
Correlation Technique ◽  
Pipeline System ◽  
Pipe Network ◽  
Cross Correlation Analysis ◽  
Valve Position ◽  
Single Sensor ◽  
The Cross ◽  
Cross Correlation Technique

The pipeline systems used to carry liquids and gases for the ventilation of buildings, water distributions networks, and the oil and chemical industries are usually monitored by a multiplicity of pressure, flow, and valve position sensors. By comparing the input signal to a valve with the pressure reading from the network using cross-correlation analysis, the technique described in this paper enables a single sensor to be used for monitoring. Specifically, the offset and gradient change of the cross-correlation function show the time delay between the input wave and the acquired output signal. These reflections arise from junctions, valves, and terminations, which can be located effectively using the cross-correlation technique. Investigations using a T-shaped pipe network have been conducted with a valve inserted in the pipeline to introduce artificial water hammer-type perturbations into the system. Both computational and experimental data are presented and the results are compared with the actual pipe network geometry. It is shown that it is possible to identify the location of various features of the network from the reflections and thus to perform either system characterisation or condition monitoring.

scholarly journals Investigations on the Coregistration of Sentinel-1 TOPS with the Conventional Cross-Correlation Technique

2018 ◽  
Vol 10 (9) ◽  
pp. 1405 ◽  
Author(s):  
Yuxiao Qin ◽  
Daniele Perissin ◽  
Jing Bai
Keyword(s):  
Cross Correlation ◽  
Phase Error ◽  
Impulse Response Function ◽  
Correlation Method ◽  
Correlation Technique ◽  
Geometrical Approach ◽  
Rigid Transformation ◽  
Interferometric Phase ◽  
The Cross ◽  
Cross Correlation Technique

In Sentinel-1 TOPS mode, the antenna sweeps in the azimuth direction for the purpose of illuminating the targets with the entire azimuth antenna pattern (AAP). This azimuth sweeping introduces an extra high-frequency Doppler term into the impulse response function (IRF), which poses a more strict coregistration accuracy for the interferometric purpose. A 1/1000 pixel coregistration accuracy is required for the interferometric phase error to be negligible, and the enhanced spectral diversity (ESD) method is applied for achieving such accuracy. However, since ESD derives miscoregistration from cross-interferometric phase, and phase is always wrapped to [ − π , π ) , an initial coregistration method with enough accuracy is required to resolve the phase ambiguity in ESD. The mainstream for initial coregistration that meets this requirement is the geometrical approach, which accuracy mainly depends on the accuracy of orbits. In this article, the authors propose to investigate the feasibility of using the conventional coregistration approach, namely the cross-correlation-and-rigid-transformation, as the initial coregistration method. The aim is to quantify the coregistration accuracy for cross-correlation-and-rigid-transformation using the Cramér-Rao lower bound (CRLB) and determine whether this method could eventually help to resolve the phase ambiguities of ESD. In addition, we studied the feasibility and robustness of the cross-correlation plus ESD under different conditions. For validation, we checked whether the cross-correlation plus ESD approach could reach the same coregistration accuracy as geometrical plus ESD approach. In general, for large areas with enough coherence and little topography variance, the cross-correlation method could be used as an alternative to the geometrical approach. The interferogram from the two different approaches (with ESD applied afterward) shows a negligible difference under such circumstances.

scholarly journals Speckle Cross-Correlation Method in Measuring Fine Surface Displacements

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
M. Bahrawi ◽  
N. Farid ◽  
M. Abdel-Hady
Keyword(s):  
Cross Correlation ◽  
Correlation Method ◽  
Industrial Applications ◽  
Correlation Technique ◽  
Surface Displacements ◽  
Speckle Patterns ◽  
The Cross ◽  
And Performance ◽  
The Stability ◽  
Cross Correlation Technique

Industrial applications need regular testing for the lifetime, movement, strength, and performance of manufacturing machines during production process. Since speckle photography is a simple economic technique, it is used in investigating object response under mechanical and thermal effects depending on the movement of the speckle patterns with respect to the deformation strength and direction. In the present work, the cross-correlation technique is used to analyze the speckle patterns by iterative method to define both values and directions of rigid body translation and expansion. In order to check the accuracy of the cross-correlation technique, the results are compared with the displacement values given by analyzing the Young's interference fringes resulted from the Fourier transformation of the speckle patterns. This noncontact technique is found to be accurate and informative depending on the stability and sensitivity of the optical system. This method of measurement is an effective tool in studying the hard cases of objects and machines under various effects.

INTERPRETATION OF SEISMIC REFRACTION DATA AND THE SOLUTION OF THE HIDDEN LAYER PROBLEM

Geophysics ◽  
1970 ◽  
Vol 35 (4) ◽  
pp. 613-623 ◽  
Author(s):  
K. L. Kaila ◽  
Hari Narain
Keyword(s):  
Seismic Refraction ◽  
Thick Layer ◽  
Field Problem ◽  
Straight Line ◽  
Oil And Natural Gas ◽  
First Arrival ◽  
Basement Depth ◽  
Hidden Layer ◽  
Seismic Refraction Data ◽  
Refraction Data

A new statistical method is described for the interpretation of seismic refraction data. This method is then applied to the interpretation of a seismic refraction profile 15,220 m long shot by the Oil and Natural Gas Commission of India along the Hoshiarpur‐Tanda road in Punjab State. The 14th iteration least squares straight line fit made to the traveltimes of first refracted arrivals gives for the Hoshiarpur area five layers 144, 322, 726, 769, and 1711 m thick with velocities of 1667, 1906, 2209, 2778, and 3505 m/sec respectively above the basement at a depth of 3672±11 m. The basement velocity is found to be 6514 m/sec. Analysis of later refracted arrivals indicates the existence of a hidden layer with a velocity 4280 m/sec in the Hoshiarpur area. Due to the presence of the hidden layer, the fifth layer with a thickness of 1711 m computed from first arrival analysis is split into two layers with thicknesses of 1160±10 and 752±18 m; the 752‐m‐thick layer is the hidden layer. As a result of the hidden layer, the computed basement depth increases to 3873±21 m. The importance of later refracted arrivals for the solution of hidden layer problems in refraction seismology is duly stressed. An extension of Green’s method (1962) for determining the possible range of a hidden layer thickness beneath a multiple layer overburden is given and applied to the field problem discussed in this paper.

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