In addition to the direct comparison over the track 085,
two crossover points were considered in this study, respectively
between the tracks 222 and 085 (P222/085) and
between the tracks 009 and 222 (P009/222), as shown with
diamonds in Fig. 4. According to the regional method diagram
(Fig. 1), the first case (P222/085) exactly corresponds
to the configuration of the point A and the mean profile of
the track 085 is necessary to transfer the SSH information
at the crossover point to the point of comparison on the
in situ mean surface. The second case (P009/222) is in the
configuration of the point B and the mean profiles of both
the tracks 222 and 085 must be used.