Backsight

1. A sight or bearing on a previously established survey point (other than a closing or check point), taken in a backward direction. AGI
2. A reading taken on a level rod held in its unchanged position on a survey point of previously determined elevation when the leveling instrument has been moved to a new position. It is used to determine the height of the instrument prior to making a foresight. Syn: plus sight Abbrev: BS. Ant: foresight. AGI

Source: Dictionary of Mining, Mineral, and Related Terms