In navigation and position fixing, a transit occurs when a navigator observes two fixed reference points that are in line with the navigator. This creates a position line. The intersection of two position lines tells the navigator his or her location.
Sensitive reference points for transits are far apart; the closer they are, the more difficult it is to tell if they are lined up.
Transits usually rely on visual reference points. Often that is their downfall; good visual conditions are needed to make use of them.
