Correlating a measured and predicted log. At least some illustrative embodiments are methods including: plotting values of the measured log with respect to an ordinate axis and an abscissa axis, and the plotting in a first pane; plotting values of the predicted log with respect to the ordinate axis and the abscissa axis; selecting an inflection point of the predicted log; shifting horizontal position of the inflection point relative to the measured log responsive to the pointing device; changing dip of at least one modeled surface in a structural model based the relative location of the inflection point; recalculating the predicted log based on the change in dip, the recalculating creates a modified predicted log; and then plotting the modified predicted log. In some cases, the method may also include adding a fixed X, Y, Z point in the at least one modeled surface based on location of the inflection point.