Pressure Tide Gauge

A pressure tide gauge infers water level from the hydrostatic pressure of the overlying water column, measured by a submerged sensor or a bubbler (pneumatic) system that holds a fixed gas pressure against the sea. Sea level follows from p = rho g h, so the gauge needs the local water density and a barometric correction for atmospheric pressure on the surface. Bubbler gauges site the pressure point on a fixed orifice and read level to a few millimeters, the GLOSS target. They avoid the stilling-well lag of float gauges but drift if density or the reference benchmark shifts, so each is tied to a leveled tide-gauge benchmark.