Extended Data Fig. 2: Examples of cross-correlation coefficient map in second estimation.

The vertical axis represents the northward velocity and the horizontal axis represents the deviation of the eastward velocity from the assumed background velocity. The eastward velocities were divided by the cosine of the latitude. The crosses indicate the maxima, and the blue, green and black lines indicate the contours of the top 1%, 5% and 10% values, respectively. a, b, Two examples of accepted cases. c, Case rejected because of multiple local maxima. d, Case rejected because the major axis of the region of the top 5% is longer than 60 m s⁻¹.