Fig. 1From: Vertical head rotation as major source of differences between time-separated digital cephalometric radiographs of patients acquired in one cephalostat X-ray deviceSketch of the reference points S, N and A, the SNA-angle and the horizontal angle ω. For illustration purposes, here SN in the left image is ideally orientated parallel to the horizontal plane, hence the ω = 0° in this caseBack to article page