Since the Jason-1 mission orbit change, in January 2009,
it has not been possible to monitor the altimeter bias with
the classical absolute method, as no track directly flies over
the various calibration sites any more. As it was previously
explained in Section 2, the regional calibration method can
be used for any mission and with mean profiles of various
satellites. It is consequently possible to estimate the bias of
the Jason-1 mission on its interleaved orbit by considering
crossover points around the Senetosa calibration site. The
crossing tracks can both be interleaved and nominal tracks,
as shown in Fig. 4.