occupy

To occupy a point means to position a theodolite, total station, or level directly above a marked station on the ground, aligning the instrument's vertical axis with that point. This is the foundational setup in any survey. The surveyor places the tripod legs around the station, then uses a plumb bob or optical plummet to center the instrument's axis precisely over the mark, whether it is a nail, peg, or concrete station disk.

Accurate occupation is critical because all subsequent measurements depend on knowing exactly where the instrument stands. Even a few centimeters of misalignment horizontally will introduce systematic error in all angles and distances measured from that setup. Most modern instruments include an optical or laser plummet built into the base, which projects downward through the center of the instrument to help the surveyor see whether the tripod is centered. On sloping ground or when dealing with tall tripods, this requires patience and repeated checking.

The time spent occupying a point correctly is always time well spent. A surveyor who rushes this step may find that their angles do not close properly or that backsight readings do not match forward observations. Occupation typically requires the surveyor to level the instrument if it is not self-leveling and to check the centering once more after that step, because moving the leveling screws can shift the instrument slightly over the point.

The term reflects the spatial relationship: the surveyor occupies the point with an instrument, much as a person would occupy a room. In practice, when a surveyor says "I'll occupy the west station next," they mean they will pack up and move the instrument to that location and set it up there. The word appears throughout surveying records and field notes as shorthand for this essential operation.