A kind of telemeter for measuring the distance of an
   object of known dimensions, by observing the angle it subtends;
   especially (Surveying), a graduated rod used to measure the distance of
   the place where it stands from an instrument having a telescope, by
   observing the number of the graduations of the rod that are seen
   between certain parallel wires (stadia wires) in the field of view of
   the telescope; -- also called stadia, and stadia rod.