Mariners have always used the position of the latitude and the longitude to seek directions in the sea as well as mark their relative positions in the sea. Historically, they would calculate their position by looking at the North Star Polaris with a sextant when they sailed the waters in the northern hemisphere.
GPS navigational system
Modern seafarers use the GPS or the global positioning system for accurately pinpointing their direction and their positions in the sea. The GPS system can provide accurate information in all climatic and weather conditions. It can provide information related to weather, positions, obstacles and directions anywhere on earth. However, it is important that the receiver should be in direct line of sight with the satellite in order to relay the information. GPS technology is now being used in cars, phones, aero planes and for other non military uses as well. This technology has its base in the radio based navigation systems such as LORAN and Decca Navigator that were developed towards the end of the WWII.
Mariners also use the LOP or the lines of position technique where a line of position is accurately tracked. The line can refer to the line on the charts that are used by the mariners or the line that exists between the mariner and the object, in reality.
Navigators will also use the technique of measuring distances from the objects. Effectively, the navigator will draw arcs on the navigational charts, and this will show them the distance between the ship and the object. This navigational chart is known as the nautical chart and the navigator will represent the ship on that chart.
The Dead reckoning system
Another navigational method that is used is known as the dead reckoning, where the position of the ship is fixed by using the course that the ship takes, and the speed at which it moves. The DR or the dead reckoning position also need to be corrected since the leeway of the ship, the effect of the currents in the sea and the steering error will affect the DR position as well.
The celestial sighting navigation system
The celestial navigation system is not used on its own but rather as a help to other navigational systems such as GPS. The celestial navigation system makes use of the measurements where celestial objects such as planets, and the moon have been sighted and then amalgamating these measurements using spherical trigonometry and almanacs.
Radio and radar systems
Radio navigation is still used for finding directions in the sea; however, GPS is now the preferred way of measuring distances, positions and directions in the sea. The preferred methods under this system are the LORAN-C and Decca. The radar navigation system is used for directions in the sea as well as for collision avoiding technique in the sea. Primarily, this system is used when the radar range is close to the land or when land can be sighted.
Traditionally, the devices that were used by mariners were the compass, the marine chronometer and the marine sextant.