Hannah Arends. Kirsten Rutschman

Faculty Advisor: Karll Rusch

Objective: To familiarize the crew with the history and development of nautical navigation and offer hands-on use of traditional navigational aids.

Out on the open seas, a ship is lost. If she wants to go anywhere, she needs to know where she is, where the destination is, and how to get there. Trying to find a given place without navigating is somewhat like trying to find a friend while walking blindfolded over a rocky plain: you don't know where you are, you don It have a clue where you're going, and you'll probably trip over hidden rocks or crash into other unknown obstacles.

From the earliest times, man has sailed the vast regions of the seas; therefore, the science of navigation has been around for thousands of years.

The Greeks and Phoenicians used the stars to gather their bearings, a process also used by various peoples in later times. Completely isolated from the western world, Chinese people in the 3rd century AD were quite interested m navigation They developed a carriage topped with a statue designed to point south no matter which way direction the carriage faced Most likely built using a system of gears, it would not have been accurate over long distances and uneven terrain, but it represents an important step in the search for standardized direction

One of the first major developments in terrestrial navigation was the magnetic compass. Described as early as the 4th century, the compass originally consisted of a magnetized needle floated in cork or straw in a dish of water.

The magnetic compass shows local variation, or declination, because Magnetic North is not the same as True North. Charts show the local variation/declination to help sailors measure their courses more accurately.

Additionally, the presence of iron nearby can draw the needle away from its correct position. This became a particular problem in the late 1800s with the production of iron and steel ships. The gyrocompass was developed to solve this and is based on a spinning gyroscope and the earth's rotation, allowing it to point toward True North at all times.

How far north or south am I? - The science of latitude

It is very important for navigators to know how far north or south they are. To determine this they need two pieces of information:

After astronomers had been collecting information about the movement and position of stars for many thousand years and plotting the track of the sun across the sky, they compiled this information into tables called almanacs. It was easy to find the geographical position of a particular star at a certain time by referring to these tables. The problem was that the earlier almanacs consisted of astrological symbols and other information that wasn't any help to sailors and mapmakers. Finally in 1509 a small pamphlet of 24 pages was published in Portugal which was a bigger help and told navigators how to calculate their latitude with the help of the sun and the Pole Star. It also included a list of latitudes of known places.

Many ships used a traverse board to more conveniently and accurately chart their location. Sailors kept track of direction and speed by pegging holes in a wooden board; this information was then translated into distance and direction traveled and noted on a chart. Speed was measured by using a piece of wood tied to a knotted rope; the number of knots crossing the deck as the ship traveled in a 30-second time period corresponded to the number of knots (nautical miles per hour) that the ship traveled.

While dead reckoning helped compensate for a lack of knowledge of east-west location and overcast sides, it was far from accurate. Because it doesn't consider important factors like current, errors in steering, and wind, this method proved fatal at times. One of the most tragic incidents cost nearly 2000 sailors their lives when they ran around upon fog-enshrouded islands in 1707.

The lead allowed sailors to determine their location in shallower waters, especially around islands. A weighted cone was dropped overboard on a line marked by fathoms (6-ft intervals) to measure the water's depth. The hollow bottom of the heavy lead was filled with malleable tallow to retrieve sample of the ocean bottom and report valuable information about location (bottom is rocky, sandy, etc.)

Charts (maps) were perhaps a navigator's greatest asset; because they were so rare, they became closely guarded secrets. Containing markings such as water depth, ocean bottom composition, and lighthouse location, charts provided sailors with vital information, and are still vital to modem navigation. If a ship were attacked, sailors would weight their charts and throw them overboard; under no circumstances should the enemy profit from their use!

While sailors in the early 1700s could easily measure their latitude, they had no way to determine how far east or west they were on the ocean. For generations, seamen and scientists alike sought for a solution to this problem. Respected scientists like Galileo Galilei and Sir Isaac Newton searched for a method to measure longitude in the stars, but their celestial methods were either undependable or too complicated for unlearned sailors to compute. Finally, a self-taught clockmaker named John Harrison delivered an approach from a different angle: why not develop a clock accurate enough to keep time at sea? He created the first chronometers, clocks accurate enough to carry the correct time despite changes in temperature and moisture, and rough seas. Longitude became easy to measure by comparing the clock's time, set to London, Paris or some other major city, with local high noon; the time difference is transferable into degrees of longitude, with every hour corresponding to fifteen degrees of latitude and four minutes of time equaling one degree.

As technology has developed in every technical field it has also developed and improved navigation. The cross - staff, quadrant and other traditional navigational aids have been good enough in the past, but they don't provide ships with enough exact information anymore and have been replaced with modern electric navigational systems such as radio, radar and GPS.

Radio: The radio was the start of electronic navigation after it was first used on ships and airplanes in the early 1900's. To find one's way with the help of radio signals the navigator moves the antenna of a radio direction finder (RDF) to locate the direction of a radio beacon. A radio beacon is a bearing of a transmitter. The RDF notifies the navigator as soon as the antenna points toward the beacon. Usually radio direction finding is used along coastal waters and the range of RDF signals depends on the type of radio beacon.

Radar: A radar system is based on the transmission of radio signals toward an object and the reception of the signals that are reflected from the object, the returning signals create an image on the radar screen. Which allows navigators to figure out the direction and distance from the object to the vehicle.

Radar can help navigators in many ways, such as carrying out a piloting operation by locating the vehicle's position in relation to landmarks at night or in bad weather; it also prevents collision with other vehicles and locates obstructions. And, of course, navigators use radar to track the position of ships (or airplanes, missiles, spaceships).

GPS: GPS is a worldwide satellite system that was started by the United States in the 1970's and then became fully operational in the year 1995. Satellite navigation itself began in 1960 with the TRANSIT IB satellite.

The Global Positioning System (GPS) includes 24 Navstar satellites controlled by the U.S. Air force. Navstar stands for Navigation Satellite Tracking and Ranging. These 24 satellites circle the Earth in six different orbits, and each of them broadcasts its exact position and the time. A computerized receiver on a vehicle analyzes how long it takes the broadcast from at least three different satellites to reach it. The receiver then determines its location by calculating its distance from these satellites. The GPS makes it possible for all types of vehicles on the Earth and in the air to find their position under all weather conditions. There are even GPS receivers, which can be held in a hand and used outside of a vehicle.

Here's an activity for you: locate our current position and mark it on a chart.

Method: identify two visible points on a chart. Sight each point with a compass and record the directions. Extend the directional lines on the chart; our location is the point of intersection.