Target geometries, Olympic 70M vs Big Shoot, frontal view. The thumb and human figures are added for perspective, with the thumb scaled to 2° (width) at the first joint, following a rough astronomical ‘rule of thumb’, and the human figures scaled to an arm-span of 8 chi (184.8 cm) and foot-length of 1.2 chi (27,72 cm), according to Zheng Xuan’s figures.