A NOAA surveyor is leveling from a tidal staff (top of staff visible to left of observer's right leg)

A NOAA surveyor is leveling from a tidal staff (top of staff visible to left of observer’s right leg). Bench marks such as the one displayed in the previous image are set and leveled to from the bench mark to help assure the staff has has not moved vertically during the course of a series of tidal observations and that an accurate tidal datum has been established in the area.