Abstract: A new method by using the expression for the surfaceimpedance of the earth with finite conductivity presented, and the results of horizontal field calculated from wave tilt and surface impedance with exact expression is compared. The new method is suit for calculating horizontalfield generated by return strokes at distances as close as 200m, while these close ranges the use of the wave tilt expression can cause large errors.

Key words: electromagnetic field, horizontal field, surfaceimpedance method