Better time picks=better travel times=better velocities: progress in developing public-domain software

John F. Hermance; Rabi N. Bohidar

doi:10.1117/12.462303

12 April 2002 Better time picks=better travel times=better velocities: progress in developing public-domain software

John F. Hermance, Rabi N. Bohidar

Proceedings Volume 4758, Ninth International Conference on Ground Penetrating Radar; (2002) https://doi.org/10.1117/12.462303
Event: Ninth International Conference on Ground Penetrating Radar (GPR2002), 2002, Santa Barbara, CA, United States

Abstract

Recognizing the importance of quantitative estimates of GPR velocities, we have implemented several standard approaches as public domain software. A field observation that a rainfall event of 3.5 cm was associated with a decrease in the velocity of a shallow reflected phase from 0.104 to 0.085 mlns, along with antecedent literature on the effects of soil water on GPR velocities, underscored the potential hydrological applications of such results. The algorithms we favor are robust in implementation, provide accurate results, yet are based on methodologies readily grasped by nonspecialists and beginning students. Some applications involve such housekeeping elements as format conversion; filtering; gain options; and resampling using FFT interpolation. More useful to the general user are analysis packages for research and teaching: NMO/LMO velocity scans; time-base stretching; event picking; windowed scaling; optimal stacking; and cross-correlation analysis. Testing our procedures on an air wave phase, its velocity from zero-break picks was 0.27 1 m/ns, and from thresholdbreak picks was 0.284 m/ns. These are inconsistent and biased low. However, a cross-correlation procedure with an optimized native wavelet provided an estimate of 0.304 mlns, much closer to the expected value. Such routine checks corroborate the accuracy of particular procedures, and identify potential timing problems.

Citation Download Citation

John F. Hermance and Rabi N. Bohidar "Better time picks=better travel times=better velocities: progress in developing public-domain software", Proc. SPIE 4758, Ninth International Conference on Ground Penetrating Radar, (12 April 2002); https://doi.org/10.1117/12.462303

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