Meaning of dead reckoning

dead' reck'oning

Pronunciation: [key]
— Navig. Navig.
  1. calculation of one's position on the basis of distance run on various headings since the last precisely observed position, with as accurate allowance as possible being made for wind, currents, compass errors, etc.
  2. one's position as so calculated.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.