The main problem in polar navigation is one of direction, and the problem has two facets. First we have to measure direction and then we have to describe it. Generally, the seaman has a gyro-compass by which he can measure the heading of his ship. As you know, the gyro-compass is simply a gyro which keeps pointing towards the pole. If we have a gyro close to the north pole and pointing north, it will continue to point in the same direction however the ship turns beneath it. So also will it continue to point in the same direction if the Earth turns beneath it. In twelve hours it will be pointing south instead of north.