Sea level estimation

Sea level elevation for real time display is estimated from absolute pressure measurement using the following equation.

d = {(P_a ─ P_b) x 1000 / (ρ x g) }  ─ offset

d           :    Sea level elevation (cm)
P_a         :    Measured absolute pressure (mb)
P_b         :    Annual mean local barometric pressure at sea level (mb)
ρ           :    Water density (1.020 g/cm³)
g           :    Gravitational acceleration (980.665 cm/s²)
offset   :    Referencing to a datum