Fig. 7. Comparison of the two methods, V_S (flow noise) and V_K (kinematics), used to estimate speed of the body during descent and ascent (dark grey dots). The slope of the least-squares linear regression (blue line; N=4062, r²=0.91, P<0.001) through all data points is not significantly different from unity (red line). Note that V_S tends to underestimate V_K at speeds greater than 5 m s^–1, the highest speed for which flow noise was recorded by the towed wing (Fig. 3).