ESDU 98026 provides an example of the use of similarity rules in the correlation of measured data for a complex aerodynamic case in a relatively simple way. The particular case considered is the base drag coefficient of conical afterbodies in axisymmetric flow (jet off). In this example the similarity rules are used only to identify the form of variables to be used in a process of correlation. The subsequent process of curve fitting is approached intuitively and is not based on any specific statistical process. The exercise can therefore be adapted to other equally complicated aerodynamic circumstances without compromising any part of the approach. An introduction to the use of the methods of subsonic, transonic and supersonic similarity is given in ESDU 97025.