COMPARATIVE PERFORMANCE EVALUATION OF IMPORTED AND LOCALLY FABRICATED ELECTRICAL RESISTIVITY METERS FOR SUBSURFACE INVESTIGATIONS

Abstract

Comparative study on performance of an imported (Ohmega) resistivity meter (RMA) and a locally fabricated (PZ-02) resistivity meter (RMB) was carried out with a view to evaluate the data measurement accuracy and reliability. Four 2-D resistivity profiling and twelve vertical electrical soundings (VES) were acquired from two study sites within Elizade University campus. The dipole-dipole and VES datasets obtained were statistically analyzed. 2-D Subsurface modeling was carried out using Dipro inversion software; while VES data interpretation was done through manual partial curve matching and WinResist iteration for geoelectric models refinement. At Site 1, the dipole-dipole analysis statistically revealed divergent performance rating for both resistivity meters. The poor statistical agreement at Site 1 was attributed to extreme outlier readings at specific electrode positions. The 2-D resistivity structure obtained at Site 1 revealed that both resistivity images did not delineate similar subsurface structure, with significant variation in RMS error; RMA (0.0961) and RMB (0.3489). At Site 2, the dipole-dipole data analysis for both resistivity meters showed very close agreement, as confirmed by the statistical analysis results. The 2-D inversion RMS errors of 0.0615 (RMA) and 0.0990 (RMB) support that the performance of both resistivity meters closely agree at Site 2. Obtained H, HA, KH VES type curves distributed across six depth sounding curves; shows 50% agreement. The comparative assessment shows that the performance of locally fabricated resistivity meter (RMB) is within acceptable limit, when compared to that of the imported resistivity meter (RMA) in near subsurface geophysical investigation.