Stadia mark

The term stadia mark derives from the obsolete unit of distance, the stadion, derived from the Greek measurement of a stadium.

A typical surveyor's instrument reticle has two pairs of stadia marks.

One pair are on the horizontal centreline and the other on the vertical cross hair.

The stadia marks are set a specific length apart.

For example, a typical stadia mark pair are set so that the ratio is 100.

Stadia marks on a crosshair while viewing a metric levelling rod . The top mark is at 1.500 m and the lower is at 1.345 m. The difference between the rod readings is 0.155 m, yielding a distance to the rod of 15.5 m.