Ford has beaten General Motors for the first time in nearly a century, in terms of number of US factory workers. Ford has 50,703 to GM's 50,300 or so.
Answers. Well, the simplest answer is that the astrolabe pretty well had to be used at night and could not be used in bad weather. The compass, which relys on the magnetic field of the Earth rather than a visualiztion of the stars, works at any time, and in any weather.
Astrolabes were quite difficult to use at sea because of the rolling of the ships, which made it hard to determine the vertical line accurately. However, they could be used on shore, and the latitude of every port and headland must have been recorded in the books of nautical instruction or rahmaanis.