[技術] Compass的操作

http://stackoverflow.com/questions/4819626/android-phone-orientation-overview-including-compass
http://disanji.net/2011/01/31/android-car-compass/
http://android-er.blogspot.com/2010/08/simple-compass-sensormanager-and.html
http://www.netmite.com/android/mydroid/cupcake/development/samples/Compass/src/com/example/android/compass/CompassActivity.java