Interference fringes with a tilted wavefront are spatially scanned perpendicularly to the carrier fringes and analyzed using FFT algorithm. It is not necessary to use any device in order to modulate interference fringes temporally. Itis also not necessary to locate fring centers and to assign interger order number. In this paper. we propose these techniques for determining the topography of a wavefront from an interferogram. The accuracy is higher then standard deviation of 1/50 wavelength.