Estimation of the error made in Pole–Dipole Electrical Resistivity Tomography depending on the location of the remote electrode: Modeling and field study

Analysis of the Influence of the GPS Errors Occurred While Collecting Electrode Coordinates on the Electrical Resistivity of Tumuli

“…To evaluate the influence of considering GPS-error in generating apparent resistivity data, the error in the geometric factor (δk flat and δk topo , respectively) was calculated, for both the flat and topo models, defined as follows (see also: [29,30]):…”

“…The second kind of error is caused by a wrong positioning of the electrodes and/or by ignoring the topography in the inversion procedure [23][24][25][26][27][28][29][30]. In particular, a wrong electrode positioning can occur: (a) when electrodes are set up by means of a tape or a string (and therefore a human error can occur), (b) when the interelectrode distance is equal to the cable fixed-space between two connections, but the cable could not be properly stretched because of the topography conditions and the terrain roughness, (c) when some electrodes have to be moved from their theoretical position to be better coupled with the soil (because of the topography and/or the presence of rocks), and d) when the finite cable length does not allow one to place the remote pole/s at the theoretical infinite distance (according to the chosen array).…”

“…In the earth sciences field the electrode-spacing error is not always taken into account during field work, and therefore, it is a quite often an overlooked problem. Nevertheless, each kind of array is affected in a different way by the errors occurred in a wrongly placement of at least one electrode [14,[23][24][25]29]. First of all, the electrode-spacing error is higher in arrays with a smaller distance among the electrodes because the percentage error is higher [14,15,24].…”

“…Then, the dipole-dipole (DD) array is the most sensitive to mispositioning errors [14,25] because the changes of its geometric factor are proportional to the cube of the distance between current and potential dipoles. In a pole-dipole (PD) array, electrode-spacing errors can also be caused by the position of the remote pole, that is commonly assumed to be located at an infinite distance from the ERT line [26,27,29,30]. Razafindratsima and Lataste [29] discussed the results of inverted models and field surveys performed to evaluate the errors in apparent resistivity and geometric factor using both the infinite theoretical distance and the finite real position of a remote electrode.…”

“…In a pole-dipole (PD) array, electrode-spacing errors can also be caused by the position of the remote pole, that is commonly assumed to be located at an infinite distance from the ERT line [26,27,29,30]. Razafindratsima and Lataste [29] discussed the results of inverted models and field surveys performed to evaluate the errors in apparent resistivity and geometric factor using both the infinite theoretical distance and the finite real position of a remote electrode. They concluded that it is always better to use the real remote electrode position instead of putting it at theoretic infinite distance.…”