Geodetic references for the altimeter and tide gauge measurements.
The altimeter SSH is directly evaluated with reference to the ellipsoid, so it
integrates the solid, polar and loading tides variations. Consequently, the
altimeter SSH must be corrected from these effects. On the contrary, the
tide gauge is fixed to the ground and moves with it, undergoing the
variations due to these phenomena. The tide gauge SSH thus do not
contain these variations and must not be corrected from them.