Exemplified by the fathoming data of a survey line using direct current, the sectional drawings of apparent resistivity isograms were plotted by manual and Surfer software respectively. It is concluded that the plotting of the isograms by correct utilization of Surfer software is of great importance. The key points for an ideal effect include the presentation of the x and y value before mesh generation, the choice of the interpolation methods and the correct interpolation. If the plotting is incorrect, the explanation of the data can be directly affected and even a wrong conclusion will be reached.