NAUPAR explains: navigating on the water. How do you do that?
Lelystad, 29 July 2015 – How do you get from A to B on the water? There are no signs, roads or other handy pointers that you have at your disposal on land. Don"t panic: there are basic practical tools that are excellent for marine navigation.
You use a compass to determine the direction in which the vessel is sailing and to take bearings from certain features. For example, a church tower on land that enables you to establish your precise location on the water. A magnetic needle that always points North is suspended in the compass. When you move the compass or the ship changes course and the compass is in a fixed location, the rose of the compass moves accordingly. The needle continues to point North, so you always know the direction in which the ship is sailing.
The distance travelled and the speed of the ship can be measured with the log. A commonly used log is the patent log – a vaned rotor connected to a log clock is towed through the water. As the ship moves the rotor spins and this movement is transferred to the counter in the log clock that then indicates the distance travelled on the water.
These days a great many ships also have GPS (Global Positioning System) on board. GPS accurately keeps track of the ship"s location. A GPS consists of three different aspects: satellites, receivers and ground stations. The GPS satellites orbit the earth at an altitude of approximately 20,000 kilometres in six trajectories, circling the earth completely every twelve hours. Signals are sent to the earth constantly during this flight, which are then received by the GPS receivers. The receivers then use the signals to determine the precise location of the vessel.