The Art and Science of Navigation
- On 23 09 2010
Another more simple definition of Navigation is the art of getting from one place to another, safely and efficiently. We all navigate every day all of the time in moving around - but we need a special set of skills to navigate at sea. In the dim and distant past small boats simply stayed close to the shore and navigated by sight of familiar landmarks or land characteristics that they could see. As boats got bigger and began to carry goods for trade, from about 3500 B.C., they needed to be able to move further so they had lists of directions but no charts yet. This could have been seen as the birth of navigation.
When they began to venture out of sight of land they used the sun by day and the North Star by night to determine direction. The simplest form of navigation is knowing where you are by remembering where you have come form. This measuring of time and direction is still vital in navigation - dead reckoning navigation. Early coastal navigators also measured depth - we know the Egyptians did around 1500BC. In the China Sea and Indian Ocean, a navigator could take advantage of the fairly constant monsoon winds to judge direction. This made long one-way voyages possible twice a year.
Navigators also used early aids to navigation such as bonfires set on hills and mountains and these progressed into the first lighthouse (the Pharos of Alexandria) around 270BC. (Our own Hook Head lighthouse is Ireland's oldest dating from the 1100's) Huge trade was carried on in the Mediterranean and the Greeks and Phoenicians began to create charts to record and plan their journeys.
In China between 1040 and 1117, the magnetic compass was being developed and applied to navigation. This let masters continue sailing a course when the weather limited visibility of the sky. Navigation tools such as the magnetic compass, using a pivoting needle in a dry box, and the lead line began to appear in the 13th century. The charts they used were made on goat or sheep skin and were very rare and valuable. In the 1400s huge strides were made in navigation with the use of the cross staff and astrolabe progressing to the sextant for measuring the height of the sun and stars. This gave mariners the ability to calculate latitude but inaccuracies in clocks made it very difficult to calculate longitude correctly. The commercial activities of Portugal in the early 15th century marked an epoch of distinct progress in practical navigation. These trade expeditions sent out by Henry the Navigator led first to the discoveries of Madeira, the Azores and the Cape Verde Islands. In the 15th and 16th centuries, Spain was in the vanguard of European global exploration and colonial expansion. Spain opened trade routes across the oceans, specially the transatlantic expedition of Christopher Columbus in 1492. The Crown of Spain also financed the first expedition of world circumnavigation in 1521.
A major advance that made dead-reckoning much more accurate was the invention of the chip log (c.1500-1600). Essentially a crude speedometer, a light line was knotted at regular intervals and weighted to drag in the water. It was tossed overboard over the stern as the pilot counted the knots that were let out during a specific period of time. From this he could determine the speed the vessel was moving. We still refer to speed at sea as knots. The first accurate representation of the spherical earth surface was the Mercator Projection (Gerardus Mercator 1569). Of great value to navigators because a compass bearing could be shown as a straight line (and they could, therefore, sail the shortest distance between two points), but the problem of determining longitude delayed the use of these charts for some seventy years after they were introduced.
The problem of inaccurate timekeeping needed to be addressed so prizes were offered for the invention of an accurate chronometer. The British prize was won by John Harrison in 1764 for his seagoing chronometer accurate to one-tenth of a second per day. James Cook used Harrison’s chronometer to circumvent the globe and when he returned in 1779 his calculations of longitude based upon the chronometer proved correct to within 8 miles. A scientist and accomplished surveyor, Cook completed such accurate and detailed charts during his voyage that he changed the nature of navigation forever and charts were rapidly developed around the world.
In 1884, by international agreement, the meridian of Greenwich, England was adopted as the Prime Meridian (0° ). Prior to that, all of the seafaring nations had their own prime meridians(ie the Spaniards used Madrid, The French Paris and so on), causing longitude to be different on charts created in different countries.In 1891, radios, in the form of wireless telegraphs, began to appear on ships at sea.
The 20th century has seen advances in navigation tools beyond anything Columbus might have imagined. The impetus for these developments was no longer trade and exploration, but for use in war. However, many of these instruments and technologies have been adapted for peacetime use. We have become so dependent on using electronic navigation that most recreational boaters today don’t know how to plot a dead-reckoning course!
British physicist Robert Watson-Watt produced the first practical radar(radio detection and ranging) system in 1935. It is used to locate objects beyond the range of vision by projecting radio waves against them.
The hyperbolic navigation system known as Loran (Long RangeNavigation) was developed in the U.S. between 1940 and 1943. It uses pulsed radio transmissions from master and slave stations that are received onboard and recorded as small waves on the screen of a cathode-ray tube. The distance between the waves corresponds to the difference in time between the arrival of the signals from the two stations. The same system was used in Europe for DECCA navigation.
During the 1970's the Royal Yachting Association and the Irish Sailing Association began to introduce navigation courses. These courses are revised progressed and developed anually and we now have a comprehensive range of courses on offer including the Basic Navigation and Safety Course, the Day Skipper Navigation Course and the Yachtmaster Offshore Navigation Course available in may schools.
GPS (Global Positioning System), initiated in 1973, is operated and maintained by the U.S. Department of Defense. This space-based radio-navigation system consists of 24 satellites and provides accurate positioning to within about 30 feet as well as velocity and time worldwide in any weather conditions. GPS works the same way as Loran (time difference between separate signals) but the signals come from satellites. Because you can receive GPS signals using small, inexpensive equipment it is being used in many new applications.
Electronic integrated bridge concepts are driving future navigation system planning. Integrated systems take inputs from various ship sensors, electronically display positioning information, and provide control signals required to maintain a vessel on a preset course. The navigator becomes a system manager, choosing system presets, interpreting system output, and monitoring vessel response.
The small boat navigator has benefited hugely from progress in navigation due to war of commercial needs. Most small boats now have and electronic log for measuring distance and speed, an electronic depth sounder, and a set of charts aboard as well as a watch. This is enough to navigate with but we have more--- anemometer to measure wind speed and direction and a chartplotter which uses GPS to put the position of our vessel on an electronic chart on a screen. Many boats also have AIS and RADAR to see other vessels in the area.
So as you can see there is a lot to the Art of Navigation. SailCork has pioneered the teaching of navigation for leisure sailors in south of Ireland. Eddie English has been running navigation courses for over 30 years and SailCork have been the first to develop new courses for each area of navigation. Eddie has produced over 2,000 graduates from his courses in Cobh, Cork, Crosshaven and other venues all over Ireland. The SailCork series of navigation courses are extra special in that they embrace the syllabus of the RYA and ISA with special SailCork additions and a very special section on Meteorology.
The simplest course for beginners is BASIC NAVIGATION and SAFETY COURSE. It includes charts and publications,safety, engine checks, buoyage, tidal awareness, visual and electronic navigation, pilotage, rules of the road, anchoring, weather forecasts and passage planning. This SHORT course is run over 3 EVENINGS.
The DAY SKIPPER NAVIGATION COURSE provides a comprehensive introduction to cruising for inexperienced skippers. This course equips you with enough knowledge to navigate around familiar waters by day. A basic knowledge of lights is also included to introduce you to night cruising. It is run over 18 evenings from early October or over a number of w-ends.
The syllabus includes: basics of seamanship, essentials of coastal navigation and pilotage, chartwork, electronic charts, position fixing, plotting a course to steer, weather forecasting and meteorology, tides, collision regulations, construction, parts and equipment of a cruising boat, emergency and safety procedures including distress calls,use of flares, safety harnesses, lifejackets and liferafts
The YACHTMASTER OFFSHORE NAVIGATION COURSE is the advanced course for more experienced skippers building on the Day Skipper course.
This course equips you to navigate safely on coastal and offshore passages. It allows some time for revision of the basics and then moves on to advanced navigation techniques. It is run over 18 evenings from early October or over a full week in the spring. Syllabus includes:position fixing, course shaping and plotting, tidal knowledge, use of almanacs and admiralty publications, electronic position finding equipment, taking and interpreting forecasts, plotting weather systems, weather predictions using a barometer and by observation, collision regulations, customs and excise regulations for cruising abroad.
Qualifications are becoming more and more important to boat users for insurance and or course for chartering. SailCork offer a fully comprehensive service from basic beginner to all the theoretical and practical qualifications. It makes sense to know what you are doing when you are afloat and remember safety comes first!