theodolite

noun

Etymology: From New Latin theodolitus (1571), perhaps containing Ancient Greek θέᾱ (théā, “sight, view”) and Arabic العِضَادَة (al-ʕiḍāda, “astrolabe, alidade”); if so, doublet of alidade.

1. A surveying instrument, consisting of a small mounted telescope, used to measure horizontal and vertical angles.

   “I drew outlines (according to my usual custom) of all the hills on the horizon before us, and took angles on them with the theodolite.”

   “The height of those mountains was from five to seven thousand feet above our level, by angular measurement with a theodolite.”