stadia

1. 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.
2. (historically) A graduated brass triangle used to measure the distance of a target by comparison of the graduations with the heights of soldiers or horses.

noun

A Greek unit of measurement, equivalent to six plethra or six hundred podes, which, though varying in precise length, is generally accepted to be equivalent to approximately 185·4 metres.

1. A venue where sporting events are held.
2. An Ancient Greek racecourse, especially, the Olympic course for foot races.
3. A Greek measure of length, being the chief one used for itinerary distances, also adopted by the Romans for nautical and astronomical measurements, equal to 600 Greek or 625 Roman feet, or 125 Roman paces, or to 606 feet, 9 inches.
4. A kind of telemeter for measuring the distance of an object of known dimensions, by observing the angle it subtends.
5. 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.
6. A life stage of an organism.