Galactic longitude and latitude of members of λ Ori. The ellipses are centred on the estimated 2D centre of mass (see Sect. 3.2) and fitted to the cluster member positions by least squares (see Sect. 3.3). The dashed line indicates the semi-major axis of the best-fit ellipse, which has an eccentricity of 0.695 and an orientation of the semi-major axis at 24.3° counterclockwise to the direction of positive Galactic longitude. The solid lines indicate the division of the elliptical annuli into different sectors, which are used to calculate the ADP (δ_ADP,e,N).