Azimuth calculation for buried pipelines using a synthetic array of emitters, a single survey line and scattering matrix formalism

BULLO, DARÍO; VILLELA, ALMENDRA; BONOMO, NÉSTOR

JOURNAL OF APPLIED GEOPHYSICS

ELSEVIER SCIENCE BV

Año: 2016 vol. 134 p. 253 - 266

0926-9851

We evaluate thesimultaneous application of a synthetic-emitter array (SEA) methodology andformulation derived from the analysis of the rotation transformations of thescattering matrix (RTSM) to calculate the orientation of buried pipes from GPRdata acquired along a single survey line. The main objective of this study isto analyze if the SEA-RTSM combination can improve the azimuth calculationobtained from the usual single-offset-RTSM (SO-RTSM) procedure. This possibility is basedon the SEA ability ofincreasing the continuity and amplitude of the primary reflections with respectto the background clutter and noise, which is expected to reduce thefluctuations involved in the RTSM calculation of the azimuth, so that its accuracyand precision are improved.  A SEA methodology designed to be used in conjunction with the RTSM methodology is described. A procedure that optimizes the results of the SEA methodology is explained.A statisticalRTSM calculation is adopted in order to obtain the final azimuth. Different relevant parameters of the soil and the array of emitters arevaried in order to evaluate the SEA-RTSM methodology and its results.Numerically simulated and experimental data are used in this evaluation. The SEA-RTSM and the SO-RTSM results arecompared between them. Theseresults are also compared with an equivalent Common-Midpoint-RTSM (CMP-RTSM)calculation. Improved precision and accuracy are obtained from the SEA-RTSMmethodology in the great majority of the examples. The height/width of theresulting azimuth distribution increases 102 % in average when using thisprocedure instead of the usual SO-RTSM procedure, the average standarddeviation diminishes 12 %, and the average differences between the calculatedand true azimuths reduces 34 %. Minor improvements with respect to SO areobtained with the CMP-RTSM methodology. The proposed SEA-RTSM methodology andits results are especially relevant in civil engineering applications in whichit is necessary to know the azimuth with precision and it is not possible toacquire data following 2D grids due to obstacles in the soil surface.