Abstract : Dealing with a surface's form is an essential part of any topographical study of the said surface's roughness. We present here a method for automatic correction of the form, using very simple concepts to solve a problem where top notch technologies were not enough mature to tackle. After explaining how well known mathematical tools such as the correlation function relate to this problem, we will see how they helped us to design an automatic procedure that we applied in order to get a highly reliable data set, that, in turn, underpinned a fine grain study on rough surfaces conducted at ArcelorMittal Research.