Fig. 1

Stacked bar graph of measurement counts per year used in deriving CM6, where “NS” and “EW” denote North–South along-track and East–West across-track, respectively, “DF/SF” and “DB/SB” denote scalar and vector differences and sums, respectively, and “SATF”, “SATB”, and “OHMB” denote satellite scalar, vector, and observatory vector measurements, respectively