Supporting information Text S1.
We conducted an investigation to establish that the range precision is comparable between the measurements from the two satellites. We apply the two-pass waveform retracker proposed by Sandwell and Smith (2005) to enhance the range precision. Figure 3 shows estimates of noise level for Jason-1 (left) and Jason-2 (right) as a function of significant wave height for global sample tracks. For both Jason-1 and Jason-2 the range precision is improved from 68 mm before retracking to 42 mm after retracking for 2 meters of significant wave height (SWH) (red and blue curves in Figure S2) for individual points (dots in upper figures) and the median over 0.5 m SWH bins (lines in lower figures).