The area 20 km south-west of Bristol, England, provides an example of the use of stereographic methods for the purpose of interpreting the geometrical characteristics of the folding.

The first stage involves the inspection of the data presented on a map (Fig. 40a). The contrasting dip directions in the northern and southern parts of the area indicate a fold in Lower Carboniferous strata. A boundary line can be drawn between the northern and southern dips; this is the axial trace, the line of outcrop of the axial surface. The convergence and closure of lithological boundaries in the east are further evidence for a fold and the dips of bedding in the vicinity of the closure suggest that the plunge of the fold is eastwards there. The combination of an easterly closure of beds on the map and an easterly plunge suggests that the fold is an antiform.

The axial trace on the map is seen to be curved (Fig. 40a); this could be due to the effects of topography on the exposure trace of the axial surface or it could be an expression of a real curvature of the axial surface. The slight swing in the strikes of the beds on moving from west to east favours the latter explanation. This curvature makes it possible that the total geometry is non-cylindrical, a situation which warrants the division of the area into sub-areas for the separate analysis of the orientation data.