This paper presents a signal processing approach to reduce uncertainty related to the time difference estimation. The proposed method is a well-known approach that suits the location of source radiation coming from thundercloud by a lightning interferometer. The method uses analytic signals and the cross-correlation function to turn lag estimation from a maximum to a zero-crossing point. The latest is simpler because it is unique, so the uncertainty about its true value is lesser. Furthermore, interpolation calculations are not required to overcome the broadening of the maxima values for noisy signals.