4.2.5. Electrode Spacing

To understand the influence between the electrode spacing and the boundary effect, and if the electrode spacing could be a normalization parameter, or whether its effect was a fixed distance regardless of the electrode rod spacing, this study fixed the medium depth and size and set the electrode spacing as 2 m and 4 m, respectively.

When the resistivity ratio value n was 0.1 and the electrode spacing *dx* was 2, the influence distance of the boundary effect was 8 m; moreover, when the electrode spacing *dx* was 4, the influence distance of the boundary effect was also 8 m. Although the use of a smaller electrode spacing had better resolution, the influence distances were the same. Therefore, it is not appropriate to use the electrode spacing as the normalization parameter of the influence space of the boundary effect as the influence distance does not become smaller as the electrode spacing becomes smaller. This result is similar to the 3D effect of the pipeline stratum, where neither were affected by the electrode spacing.
