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.
The Surface RT tablet does not have a megnetometer, but does have a functioning compass. While I don't know of any way to resync the compass, it seems strange that it would be off. I suggest trying a different app (e.g., Maps) to see if it is truly your devices compass or the app that is off.