Generic diagram of the regional in situ calibration method. The
points A and B represent the crossover points between, respectively, the
satellite altimeter tracks 1 and 2, and the tracks 2 and 3. The tracks can
belong to different altimeter missions. The in situ high resolution mean
surface is used to link the tide gauge (TG) measurements to the altimeter
data, and the comparison is done at the point C, located on this surface.