"Effectually we looked at the Doppler effect, which is the change in frequency, due to the movement of a satellite in its orbit. What that then gave us was a predicted path for the northerly route and a predicted path the southerly route," Chris McLaughlin, senior vice president of external affairs at Inmarsat, told the Daily Telegraph.
"They've tested it off against a number of other aircraft known flights and come to the conclusion that only the southern route was possible," McLaughlin told Sky News on Monday (local time).
"We refined that with the signals we got from other (777) aircraft and that then gives you a very, very good fit.
"Previous aircraft provided a pattern and that pattern to the south is virtually what we got in our suggested estimates."
http://www.stuff.co.nz/world/asia/9863325/How-flight-MH370s-path-was-confirmed