noun A level staff or graduated rod used by surveyors to measure differences in level, or to measure horizontal distances by sighting the stadia hairs (graduations) through a telescope.
noun Hash marks or other reticle etchings on a riflescope's lens which are used for stadiametric rangefinding; lines or curves for estimating the range of a target of known height, such as an enemy soldier or a game animal.
noun A graduated brass triangle used to measure the distance of a target by comparison of the graduations with the heights of soldiers or horses.