Dioptra

·noun An optical instrument, invented by Hipparchus, for taking altitudes, leveling, ·etc.

dioptra
dĭoptra, ae, f., = δίοπτρα, an optical instrument to measure the height of places, Vitr. 8, 6; fo...

A New Latin Dictionary by Charlton T. Lewis Ph.D. and Charles Short, LL. D.