Note:  Do not rely on this information. It is very old.

Dead Reckoning

Dead Reckoning, in navigation, is an estimation, without astronomical observation, of the position of a ship. It is found by keeping account of the distance shown by the log to have been run and of the course as steered by compass, and by rectifying these data with allowances for drift, leeway, etc. Dead reckoning is, of course, checked and corrected as often as good observations of the sun can be obtained.