1. A method for determining a bedding surface from an azimuthal image made from a signal provided by a logging tool placed in a cylindrical wellbore, said method comprising: determining, using a computer and based on minimum variance, a best sine wave in the the minimum variance represents a minimum value in a variance map of sine waves of the azimuthal image; computing contrast at each selected depth along the best sine wave in the azimuthal image; and locating one or more bedding surface boundaries at one or more depths with highest contrasts.