Altimetry refers to the measurement of altitude or height above sea level. It is a way to determine how high or low something is in relation to the ocean's surface. Full definition
Variations in global mean sea level (difference to the mean 1993 to mid-2001) computed from satellite altimetry from January 1993 to October 2005, averaged over 65 ° S to 65 ° N. Dots are 10 - day estimates (from the TOPEX / Poseidon satellite in red and from the Jason satellite in green). (ipcc.ch)
Description: based on 4.5 years of GRACE data, and 15 years of altimetry and in - situ data (hydrologic and drifters data). (aviso.altimetry.fr)
To get the biggest picture now available, Paolo and his colleagues stitched together satellite radar altimetry data from three consecutive and overlapping missions: the European Space Agency's (ESA's) ERS - 1 and ERS - 2 (which flew from 1991 to 2000 and 1995 to 2011, respectively), and ESA's ENVISAT mission, which collected data from 2002 to 2012. (sciencemag.org)