The method of projected fringes is applied to the measurement of the surface topography of aluminum ingots with surface areas of several square meters. The measurements are performed inside the casting hall of an aluminum factory. To meet the challenges encountered in such a demanding environment, it is important to keep the equipment as simple and robust as possible. Therefore a method for locating the fringe positions with sub-pixel accuracy without using for example phase shifting techniques is applied. Also the nonlinearity of the phase when using divergent illumination is discussed. The developed measuring system is tested measuring eight different aluminum ingots, and the results agree very well compared to a standard manual measurement method.