Dictionary:Stadia tables

Tables giving values of the quantities (sin2α)/2 and cos²α and/or sin²α as functions of α. Used in calculating horizontal (H) and vertical (V) distances from a transit station to a stadia rod. If α is the angle which the line of sight makes with the horizontal, F is the stadia interval factor (often 100), and X is the distance on the rod between the cross hairs, then H=FXcos²α=FX–FXsin²α, and V=FX(sin2α)/2.