Although the subject of engineering surfaces covers a large number of interdisciplinary subjects ranging from, say, economics on the one hand to chemistry on the other, there are a number of areas in which a degree of unity can be seen. One of these, perhaps the most important, is in the processing of measured information to enable it to be used most effectively for control of production or design purposes. Processing information is taken to mean making changes to the original data to isolate, separate, or identify features which may be of particular signicance. Certain operations which keep on recurring will be highlighted. There are also other considerations which accompany processing such as ltering. For example, in some cases it may be necessary to construct surface pro-les or areal maps from signals obtained from a surface by means other than by scanning i.e., optical diffraction or it may be necessary to investigate ways of generating surfaces in the computer data from. In this section a few of these will rst be described and then illustrated with particular reference to some of the issues pertinent to the subject matter being discussed. Parts of the chapter will be tutorial in character to help ensure that a common base of understanding is available.