A two-dimensional, circular representation of a sphere in which the lines of longitude and latitude form a system of coordinates (a ‘net’), on which projections of great and small circles occupy the equatorial plane of a reference sphere. Two types of stereonet are used in the analysis of structural data: an equal-angle net (Wulff net); and an equal-area net (Schmidt–Lambert net), which is the net preferred for the contouring of data and the evaluation of clusters of data suggesting preferred orientations.