the·od·o·lite 
(thē-ŏdl-īt′)
(thē-ŏdl-īt′)n.
An optical instrument consisting of a small mounted telescope rotatable in horizontal and vertical planes, used to measure angles in surveying.
[Probably coined by Leonard Digges (1520-1559), English mathematician and surveyor, as the name of a device for measuring horizontal angles, perhaps from Greek theā, a viewing + a second element of unknown origin.]
the·od′o·litic (-lĭtĭk) adj.
theodolite