ABSTRACTThe basic principles of the application of the linear system theory for smoothing noise‐degraded d.c. geoelectrical sounding curves were recently established by Patella. A field Schlumberger sounding is presented to demonstrate first their application and validity. To achieve this purpose, firstly it is pointed out that the required smoothing or low‐pass filtering can be considered as an intrinsic property of the transformation of original Schlumberger sounding curves into pole‐pole (two‐electrode) curves. Then we sketch a numerical algorithm to perform the transformation, opportunely modified from a known procedure for transforming dipole diagrams into Schlumberger ones. Finally we show a field example with the double aim of demonstrating (i) the high quality of the low‐pass filtering, and (ii) the reliability of the transformed pole‐pole curve as far as quantitative interpretation i