Physical Science - Other

Aircraft Navigation and Waypoints

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Since early man wandered from his cave, gathered some berries and meandered back to the same cave, he has been using some form of navigation. Basically, navigation is getting from one place to another, hopefully without getting lost. When man was walking around the immediate area of his cave, navigation was pretty easy; look for the things that were familiar - a rock formation, an unusual looking tree or the curve of a river. Visual navigation is the simplest form of getting from one place to another. As we began to venture further afield, the art of navigation became a bit more complicated.

The word "navigate" comes from the Latin words "navis" meaning "ship" and "agere", "to move". Early ship captains learned to use the position of the sun, moon and stars to help them get where they wanted to go. This is called celestial navigation. With the aid of a "star map", a nautical chart, a sextant and later a chronometer and compass, man began to spread across the globe and learn how to get not only where he wanted to go, but back home again. As time pasted both maps and instruments became more accurate and more sophisticated, however still depended on the skill of the person using them. Ships became faster, man discovered radio waves and both radio and radar navigation became common place.

With the advent of air travel, navigation entered an entirely new realm. Aircraft generally travel at much higher speeds and can't stop to determine where they are. They are limited in the amount of fuel they carry, making them unable to sit and wait for someone to find them if they get lost. Also, it is probably not going to end well for an aircraft whose pilot unwittingly steers the plane into the side of a mountain because of a wrong turn. Obviously, it is of vital importance for the pilot of a plane to have an accurate and up-to-the-minute picture of where he is.

The type of navigation used by pilots depend on several factors - the size and speed of the aircraft he is flying, the experience of the pilot and the distance between points A & B are some of them. Prior to the 1920's flying was limited to daylight hours. Pilots flew with a road map and a prayer. Mountains, rivers and towns were used to establish one's location. There was no radio communication, no air traffic control, no real charts or navigational aids. Anyone who wanted to could build and fly an "airplane".

In the early '20's, things began to change. The U.S. Airmail Service needed to be able to move the mail quickly and at their request a series of beacons were built. The 1,000-watt lamps were mounted on 51' towers and amplified by 24" parabolic mirrors. By 1929, a series of beacons stretched from New York to San Francisco. Spaced 10 miles apart, the one million candlepower beams helped light the dark for early pilots.

Altimeters, directional gyroscopes, two-way radios, VOR, VHF... With each advance in technology, navigation became more sure and flight became safer. Today, navigation techniques still depend on whether a pilot is flying VFR (visual flight rules) or IRF (instrument flight rules). The pilot who is flying "visual" will be flying at a lower altitude and using landmarks. Combined with tracking one's speed, course and elapsed time, these enable a pilot to pinpoint where he is on a map. This is known as "dead reckoning". For slower, low flying planes this type of navigation works well most of the time. Problems occur when weather or darkness obscure the landmarks. This is when pilots must use other means of navigation, such as radio, radar or GPS to reach their destination.

From the earliest forms of radio and beacons to the most up-to-date GPS systems, the goal has always been the same - knowing the plane's position compared to a set location. This can be either an actual location or a set of coordinates, called a "waypoint".

Waypoints came into being with the development of radio navigation, but their usage has become increasingly widespread since the development of the Global Positioning System, or GPS. Though waypoints can be tied to radio beacons, satellites or buoys, they are most often only a set of coordinates that include the longitude, latitude and (in many cases in aviation) the altitude. Waypoints can be programmed into a computer mapping program and uploaded to a GPS receiver or entered manually as a set of coordinates into a plane's computer. Many autopilot systems are combined with GPS navigation, allowing the plane to fly from waypoint to waypoint without pilot intervention.

Waypoints allow air traffic controllers around the world to safely rout all manner of aircraft - in effect creating "highways" thousands of feet above the earth. But, possibly even more important, these invisible intersections on latitude and longitude allow the pilot, flying through the darkness over the mid-Atlantic to know exactly where he is.

More about this author: Sherry Law

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