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CHAPTER 2 NAVIGATION
Latitude and Longitude - 14030_39

Aviation Electronics Technician 1 (Organizational)
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Navigation is both an art and a science. The science part is the development of instruments and procedures of navigation, along with the computations involved. The art is the skillful use of the instruments and the interpretation of the data. This combination has led some to call navigation a “scientific art.” The beginning navigators practiced the science of navigation, in that they gathered data and used it to solve a navigational problem in a mechanical way. It takes many hours of flying for navigators to realize that their total role involves not only the mechanics of navigation, but an integration based on judgement. They build accuracy and reliability into their performance by applying sound judgment based on experience. Navy navigators must be able to plan missions covering every possible situation. In flight, they must evaluate the progress of the aircraft and plan for the remainder of the mission. High-speed navigation demands that they have the ability to anticipate changes in flight conditions and make the correct decisions immediately ahead of those changes. The purpose of air navigation is to determine the direction of travel needed to end up at the desired location, to locate positions, and to measure distance and time as a means to that end. This chapter deals with the various types of navigation and the equipment used in aviation navigation. You must know and understand this information in order to train your subordinates. METHODS OF NAVIGATION Learning Objective:    Recognize the various methods of navigation. There are certain terms that you must know to understand navigation. The navigator uses these terms to express and accomplish the practical aspects of air navigation. These terms are position, direction, distance, and time. These terms are defined as follows: Position is a point defined by stated or implied coordinates. It always refers to some place that can be identified. A navigator must know the aircraft’s immediate position before he/she can direct it to another position. Direction is the position of one point in space relative to another without reference to the distance between them. Direction is not in itself an angle, but it is measured in terms of its angular distance from a reference direction. Distance is the spatial separation between two points and is measured by the length of a line joining them. On a plane surface, this is a simple problem. However, consider distance on a sphere, where the separation between points may be expressed as a variety of curves. The navigator must decide how the distance is to be measured. This distance can be expressed in various units; miles, yards, etc. Time is defined in many ways, but for our purposes, it is either the hour of the day or an elapsed interval. These terms represent definite quantities or conditions that can be measured in several different ways.    The position of an aircraft may be expressed as coordinates such as latitude and longitude, or as being 10 miles south of a certain landmark. It is vital that navigators learn how to measure quantities and how to apply the units by which they are expressed. EARTH’S SIZE AND SHAPE For navigational purposes, the earth is assumed to be a perfect sphere, although it is not. There is an approximate 12-mile difference between the highest point and the lowest point of the earth’s crust. The variations in the surface (valleys, mountains, oceans, etc.) give the earth an irregular appearance. Measured at the equator, the earth is approximately 6,887.91 nautical miles in diameter. The polar diameter is approximately 6,864.57 nautical miles. This difference of 23.34 nautical miles is used to express the ellipticity of the earth. Great Circles and Small Circles A great circle is defined as a circle on the surface of a sphere whose center and radius are those of the 2-2







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