Fig. 2. The relation between V_a and V_g-V_a for different combinations of V_w and - (A, -=0°; B, -=45°; C, -=90°; D, -=135°). In each subplot V_g varies from 1-15 m s^-1, and the isoclines represent constant V_w (2, 4, 6, 8 m s^-1). Note that A represents pure tailwind conditions and C represents pure side winds in relation to the ground vector. To ensure a biologically realistic representation, A is constrained as follows: V_g>V_a and V_g>V_w. In B, circles represent constant V_g (15 m s^-1) and a varying V_w (2,4,6 and 8 m s^-1), + symbols represent constant V_w (6 m s^-1) and varying V_g (2, 5, 8 and 11 m s^-1), see Fig. 3 for the individual vectors. See Fig. S1 (supplementary material: online appendix) for animated 3-D visualizations of these figures.