what is navigation?

Answer 1

The definition of navigation is: the guidance of ships or airplanes from place to place.


What is actually is is much more complex....

There are several different branches of navigation, including but not limited to:

* celestial navigation - navigation by observation of the sun, moon and stars, and sometimes planets
* pilotage - using visible natural and man made features such as sea marks and beacons
* dead reckoning - using course and speed to determine position
* Off-course navigation - allows for variables in heading by deliberately aiming to the one side of the destination.
* electronic navigation - using electronic equipment such as radio navigation and satellite navigation system to follow a course to a waypoint Also Electronic Chart Display and Information System
* position fixing - determining current position by visual and electronic means
* collision avoidance using radar

'Passage planning' An important part of the navigator's job aboard a large vessel is planning the voyage. This includes assembling the required charts, calculating tide and current, and laying out track-lines. Once the route is determined, taking into account weather, draft and other elements, the track can be laid out on a small-scale (large-area) chart. The track can then be transfered to large scale charts. When the track-line is laid out attention must be paid to depths, aids to navigation, hazards such as rocks and shoals and traffic separation schemes if any.

Once the voyage has begun the progress of the vessel along it planned route must be monitered. This requires that the ship's position be determined. Traditional maritime navigation with a compass uses redundant sources of position information to determine the ship's position. A navigator uses the ship's last known position and dead reckoning, based on the ship's logged compass course and speed, to calculate the current position. If the set and drift, due to tide and wind, can be determined, an estimated position can also be calculated.

Periodically, the navigator needs to confirm the accuracy of the dead reckoning or estimated position calculations using position fixing techniques. This is done by correctly identifying reference points and measuring their bearings from the ship. These lines of position can be plotted on a nautical chart, with the intersection being the ship's current location. Addition lines of position can be measured in order to validate the results taken against other reference points. This is known as a fix.

The earliest form of navigation was "land navigation" Marine navigation began when pre-historic man attemted to guide his craft, perhaps a log, across the water using a form of piloting which uses familiar landmarks as guides. Dead reckoning was probably next, used to navigate when landmarks were out of sight. While celestrial bodies were used to steer by, celestial navigation, as known today, was not used until the motion of the sun and stars was understood. The voyage of Pythease of Massalia, between 350BC and 300 BC is one of the best records of an early voyage. Use of magnetic compass allowing a course to be maintained. The log and a sand glass could be used to determine distance run. This allowed a dead reckoning estimate of the ship's positon to be calculated. When approaching land the lead line was used to assist with landfall. Nautical charts were developed to record new navigational and pilotage information for use by other navigators. The development of accurate celestrial navigation for taking lines of position based on the measurement of stars and planets with the sextant allowed ships to more accuratly determin position. Most sailors have always been able find absolute north from the stars, which currently rotate around Polaris, or by using a dual sundial called a diptych.

When combined with a plumb bob, some diptyches could also determine latitude. Basically, when the diptych's two sundials indicated the same time, the diptych was aligned to the current latitude and true north.
Another early invention was the compass rose, a cross or painted panel of wood oriented with the pole star or diptych. This was placed in front of the helmsman.

Latitude was determined with a "cross staff" an instrument vaguely similar to a carpenter's angle with graduated marks on it. Most sailors could use this instrument to take sun sights, but master navigators knew that sightings of Polaris were far more accurate, because they were not subject to time-keeping errors involved in finding noon.

Time-keeping was by precision hourglasses, filled and tested to ¼ of an hour, turned by the helmsman, or a young boy brought for that purpose.

The most important instrument was a navigators' diary, later called a rutter. These were often crucial trade secrets, because they enabled travel to lucrative ports.

The above instruments were a powerful technology, and appear to have been the technique used by ancient Cretan bronze-age trading empire. Using these techniques, masters successfully sailed from the eastern Mediterranean to the south coast of the British Isles.

Some time later, around 300, the magnetic compass was invented in China. This let masters continue sailing a course when the weather limited visibility of the sky.

Around 400, metallurgy allowed construction of astrolabes graduated in degrees, which replaced the wooden latitude instruments for night use. Diptychs remained in use during the day, until shadowing astrolabes were constructed.

After Isaac Newton published the Principia, navigation was transformed. Starting in 1670, the entire world was measured using essentially modern latitude instruments and the best available clocks.

In 1730 the sextant was invented and navigators rapidly replaced their astrolabes. A sextant uses mirrors to measure the altitude of celestial objects with regard to the horizon. Thus, its "pointer" is as long as the horizon is far away. This eliminates the "cosine" error of an astrolabe's short pointer. Modern sextants measure to 0.2 minutes of arc, an error that translates to a distance of about 0.2 nautical miles (400 m).

At first, the best available "clocks" were the moons of Jupiter, and the calculated transits of selected stars by the moon. These methods were too complex to be used by any but skilled astronomers, but they sufficed to map most of the world. A number of scientific journals during this period were started especially to chronicle geography.

Later, mechanical chronometers enabled navigation at sea and in the air using relatively unskilled procedures.

In the late 19th century Nikola Tesla invented radio and direction-finding was quickly adapted to navigation. Up until 1960 it was commonplace for ships and aircraft to use radio direction-finding on commercial stations in order to locate islands and cities within the last several miles of error.

Around 1960, LORAN was developed. This used time-of-flight of radio waves from antennas at known locations. It revolutionized navigation by permitting semiautomated equipment to locate geographic positions to less than a half mile (800 m). An analogous system for aircraft, VHF omnidirectional range and DME, was developed around the same time.

At about the same, TRANSIT, the first satellite-based navigation system was developed. It was the first electronic navigation system to provide global coverage.

Other radionavigation systems include:

* Decca
* Omega, a longwave system developed by the United States Navy
* Alpha, a longwave system developed by the Soviet Union

In 1974, the first GPS satellite was launched. The GPS system now permits accurate geographic location with an error of only a few metres, and precision timing to less than a microsecond. GLONASS is a positioning system launched by the Soviet Union. It relies on a slightly different geodesic model of the Earth. Galileo is a competing system, that will be placed into service by the European Union.


Later developments included the placing of lighthouses and buoys close to shore to act as marine signposts identifying ambiguous features, highlighting hazards and pointing to safe channels for ships approaching some part of a coast after a long sea voyage. The invention of the radio lead to radio beacons and radio direction finders providing accurate land-based fixes even hundreds of miles from shore. These were made obsolete by satellite navigation systems.

In the pre-modern history of human migration and discovery of new lands by navigating the oceans, a few peoples have excelled as sea-faring explorers. Prominent examples are the Phoenicians, the Ancient Greeks, the Persians, Arabians, the Norse and the Austronesian peoples including the Malays and especially the Polynesians and the Micronesians of the Pacific Ocean. With the advent of the airplane, the art of aerial navigation, an offshoot of sea navigation, was developed to account for additional effects such as coriolis effect and motion of the observer not experienced by slow-moving ships.

Answer 2

Sailor,
You of all people should know what navigation is.
A sailor cannot really be a good sailor without navigation, or he or she will end up on the rocks!
What do you think navigation is? I wonder if the word navy or navies is tied to the word navigation, because certainly navies have to navigate to get from one point to another. Sometimes they have to navigate through shallow waters with reefs which can be quite dangerous. Sometimes ships have to navigate through deep waters, so deep it is even dangerous for submarines to navigate there because the water pressure is so great. The deeper you go the higher the water pressure. Human bodies can only take so much water pressure. That is why scuba divers, even though they can go underwater with their Self-Contained Underwater Breathing Aparatus (S.C.U.B.A.) have to be careful not to go too deep. Today sailors have very sophisticated (detailed) maps that chart all the oceans of the world and tell the capitan how deep or shallow the waters are and where to watch out for rocks that might sink his ship. That would be pretty scary wouldn't it? To be on a ship that was sinking. What would you do? I would grab a life jacket and pray! A life jacket helps you float so you don't sink beneath the waves and drown. So because a Capitan doesn't want his ship to wreck (shipwreck) and his crew to drown he navigates--uses navigation- very wisely. Wouldn't you? In the old days sailors used "navigation by the stars". They used a special mechanical/optical device called a sextant to tell them approximately where they were. Now days ship captains use radar and satellites and GPS for navigation, and it is a lot safer to travel across the oceans and around the world than it was 100 years ago. Do you like homeschool? I think it is great! I think you learn a lot more and it is a lot more fun, and sometimes hard work too, but you will be smarter. But being smart is only part of it. You have to have character too. So, have you figured out what navigation is yet? I bet you have. Dictionaries are great for finding out the meanings of words--but sometimes they don't tell you very much do they? That's why sometimes it is more fun to talk about it and think it through and use brain power. "The sailor navigated skillfully through the channel, avoiding the rocks, using what he had learned in Navigation School in the Navy!"
Hope that helps Sailor.
Bon Voyage,
-Spec

Answer 3

Navigation means finding direcion and guiding a sailor en route.

Answer 4

My Garmin has been a Godsend where I'm at now. Some streets are not signposted in English, only in Chinese, so having the English maps on my Garmin has been a real boon. Also, seeing the names in the Roman alphabet, I can learn to read more Chinese characters. It has lots of other features that are useful, such as where to find garages, supermarkets, you name it. However, on the odd occasion, where roads have changed since the previous map update, I've been directed to drive into a fence, but all in all, it's great!

Answer 5

to find the way