Βασικοί όροι στη δημοσιογραφική τοπογραφία και τη γεωχωρική τεχνολογία.
The point in the celestial sphere directly above an observer's location, used as a reference direction in surveying for vertical angle measurements and astronomical observations.
The vertical angle measured from the zenith (directly overhead) downward to a surveyed point, ranging from 0° at zenith to 180° at nadir.