English: Measuring the central angle between two points P₁ and P₂ on a stereographic projection using the Wulff net. A transparent sheet has been tacked in the middle of a Wulff net and the points are drawned on the transparent sheet.
In this example, both points lie on the same parallel. The central angle can't be read along the parallel, only along a meridian: the transparent sheet has to be rotated until both points lie on the same meridian (see Wulff net central angle 2.jpg).