Pilotage
From Wikipedia, the free encyclopedia
Pilotage is the use of fixed visual references on the ground or sea by means of sight or radar to guide oneself to a destination. Pilotage is used by people guiding vessels and aircraft, by hikers and SCUBA divers. There are other, more advanced methods of navigation using tools, such as compasses, maps, nautical charts, radar and ultimately satellite navigation systems like GPS.
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[edit] Etymology
Pilotage is derived from the word pilot. The Online Etymology Dictionary traces the origin of the term pilot to the medieval Greek word pedotes denoting a steersman, this term in turn being derived from the greek podos, for the foot.
An alternate, convincing, but unlikely explanation involves the word originating from the Dutch "pyl-lood". Prior to 1550 AD the word "loods" was used all over Europe for the profession we are discussing now. The word pilot is supposed to have been derived from the word "pyl" and "lood". The word "pyl" stands in Dutch for everything vertical or straight as well as the height of the water. The word "lood" stands for "lead"; the dense metal used when making soundings. The combination of the two words describes "the person who is using the lead in a vertical way to obtain the water depths". In very ancient Dutch also the word "lodesman" is sometimes used, having more or less the same implication.
The profession of pilot and the associated word "pilotage" were first associated with maritime operations, later being extended to aircraft and other machines that require the skillful application of manoeuvring technique. While pilots are professionals, pilotage may refer to any essential activity of other professional and amateur scope involving navigation.
[edit] History
At what time in history the very first pilot appeared on the scene is pure guesswork. Obviously, it must be associated with the earliest recognition of the necessity for safe conduct of life and property.
In Biblical times pilots pursued their occupation already; see the 27th chapter of the book of Ezekiel, where the word pilot is used four times. (at least in the King James Version of the Bible; in a Netherlands version the word "sailor" is used.)
Also in the ancient writings of Homer (Homerus) and Virgil (Vergilius) there are specific accounts of the work of a pilot. Homer writes in the first book of the Iliad about Thestor the pilot "who guided ships of the Achaeans to Ilium". Virgil wrote in the 3rd, 5th and 6th book of the Aeneid about Plainurus, who piloted the fleet of Aeneas. The earliest reference to pilots, under a governing body dates from the Periplus of the Erythrean Sea. The Periplus (very ancient Sailing Direction) is one of several Periplii describing the coastal cities and their trades and provided simple directions for merchants travelling along the coast. One could compare them with today’s Admiralty Pilot Books, that are however much more detailed. For example the approach to the town of Broach 20 miles up the River Narbuda (250' NW of Bombay) is described in detail. The currents are described and the way in which the local pilots anchor in the deeper sites in order to wait for the water to rise again. These pilots were native fishermen in the King's service.
During the early Christian era, the Arabs were very active in pilotage operations and were among the first to use the magnetic compass. The first voyage of Marco Polo into the Orient was made with the help of Arab pilots. After arriving in the Great Khan's Court in 1275, Marco Polo did not leave before 1292. On the home journey Marco Polo was delayed at Sumatra, South India and Ceylon (Sri Lanka) during which time he studied the nautical charts provided by Arab pilots. Two centuries later Vasco da Gama from Portugal employed Arab pilots when navigating the Cape of Good Hope all the way to Calicut (India).
In the 1600s the defeat of the Spanish Armada is said to have been caused by the fact that it was not possible to embark the ordered pilots off Dunkirk. The Dutch were early leaders in the development of pilotage. In 1633 the Dutch East India Company commissioned pilots at Balasore, some 60 miles from the Entrance of the Hugli river. It seems that pilots in former days did sometimes belong to the ship's crew, or were sometimes stationed ashore. Their tasks were certainly not only to pilot ships, but often they were chartmakers and compilers of navigational data. Gradually clear distinctions are being made between ocean pilots and bar- or bay-pilots. For centuries the pilot who directed a ship across the ocean also brought her into port and served in a two-fold capacity, except when his unfamiliarity with the harbours made it impossible. Gradually it was recognized that expert pilotage in such cases required the local knowledge of pilots attached to the given area rather than travelling pilots skilled in general navigation.
With the knowledge of local conditions, expert shiphandling ability and by using visual references (transits), a harbour pilot provides invaluable assistance to the shipmaster when manoeuvring in the confined waters of busy ports and harbours.
[edit] Difficulties
Pilotage depends on the pilot being able to recognise the visual references in order to make use of them. The pilot must either be familiar with those visual references or be able to discover them from a map, aeronautical chart or nautical chart. Many nautical and aeronautical disasters have resulted from the pilot incorrectly identifying visual references.
Poor visibility may affect safe navigation by obscuring the natural features used by pilots in an area. In such situations, pilots use navigational aids such as radar and the GPS to determine position and monitor their passage.
[edit] Visual features
Common types of visual reference point used for pilotage:
During the day:
- Natural features: Mountains, hills, lakes, rivers and coastal features such as cliffs, rocks and beaches
- Man made nautical features: sea marks, land marks and radio aerials
- Man made land features: Airports, cities, dams and highways
At night:
- Man made nautical features: Lighthouses, lightships and sea marks with lights
- Man made land features: Airports, illuminated towers and buildings
Pilotage is frequently combined with navigation techniques such as dead reckoning. When a pilot at a known location cannot see the next visual reference on the route to a destination, he or she can use dead reckoning to get closer to the next reference point. This is the most common form of VFR navigation.de:Terrestrische Navigation fr:Navigation côtière pl:Locja
