To place a total station, theodolite, or GNSS receiver exactly over a physical ground mark to take measurements. Occupying a point requires centering the instrument using an optical plummet or plumb bob and leveling the tribrach so the instrument's vertical axis passes directly through the mark.
I'll occupy point 402 and backsight the iron pipe at 401.
Always double-check your optical plummet after leveling the instrument, as the centering often shifts during the leveling process.
Related terms
Backsight
A reading taken on a point of known coordinates or elevation to establish a reference direction.
Base station
A stationary GNSS receiver placed on a known coordinate to transmit corrections to a roving unit.
Hub
A wooden stake driven flush with the ground to serve as a temporary survey control point.