be its upward unit normal in east, north and up components. The mean orientation (or vector mean) of N readings of normals n1,…,nN is the plane whose normal is m=S/∥S∥, where S=∑ini is their resultant; Rˉ=∥S∥/N is the mean resultant length. The mean dip direction and dip are αˉ=atan2(SE,SN) and δˉ=arccos(SU/∥S∥).
Twenty-five simulated readings of the bedding of the Varden east limb, whose model attitude is 080.7/12.2, each with errors of 3∘ standard deviation on both angles, rounded to the degree. Solid line: the mean; dashed: one standard deviation either side (080.8±2.9 and 12.4±2.1). The vector mean of the 25 readings is 080.9/12.3.