Dead reckoning
From TIGHAR
"Dead reckoning (DR) is the process of estimating one's current position based upon a previously determined position, or fix, and advancing that position based upon known speed, elapsed time, and course."[1]
Noonan's task of keeping track of the aircraft's current position depended on airspeed, an estimate of the direction and strength prevailing winds, heading flown, and time elapsed since the last estimate.