The impact of geometry on 3D Resistivity/IP surveys

The Geometric Factor (k) can become infinite with a high spatial gradient for certain geometries used in Induced Polarisation (IP) surveys. This can lead to significant errors in computed apparent resistivities. Understanding the behaviour of the Geometric Factor for the different arrays used in mineral exploration is key to avoiding misleading interpretation of geoelectrical data. It is well known that at long offsets, high Geometric Factor values amplify low voltages to generate noisy apparent resistivities. However, at short offsets, equipotentials can represent an important source of noise. Practical solutions, such as varying the spacing between current electrodes or adjusting their positions along specific axes and changing the line spacing can be implemented to mitigate these geometry related issues. In conclusion, this study highlights the importance of careful geometric design in IP surveys and provides guidelines for optimising electrode configurations to obtain reliable results.