Well, the issue is: are there several north/south flowing channels?
And you want to calibrate each one?
If so, then:
"Calibration of each north/south and east/west channels
Otherwise, if there is just one channel, each flowing n/s and e/w, it would be
"Calibration of each of the north/south and east/west channels.
(meaning: calibration of each of the two channels)
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