The Altimeter measurement alows to retrieve the SSH, i.e. the heigth from the reference ellipsoid to the instantaneous sea surface.
A MSS can be used to compute the SLA, i.e. the heigth bewen the mean state of the SSH (over a specific period N, see the altimeter reference period page) and the instantaneous sea surface:
SLAN = SSH – MSSN
A MDT field can be used to retrieve the ADT, i.e. the sea surface heigth above the Geoid:
ADT = SLAN + MDTN
The difference between the MSS and MDT is the Geoid:
MSSN = MDTN + Geoid