Simplification and Classification

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Because scale reduces the size of the Earth, information must be generalized. Making the best use of available space is a major problem in chart development. The detail of the real world cannot be shown on the chart. The crowding of lines and symbols beyond a specific limit renders the chart unreadable, yet the amount of information that might be useful or desirable is almost unlimited. The smaller the chart scale, the more critical and difficult the problem; therefore, the cartographer is forced to simplify and classify information.

Simplification is the omission of detail that would clutter the map and prevent the pilot from obtaining needed information. The necessity for detail is subjective and not all will agree on what should, or should not, be included. The inclusion of too much detail runs the risk of confusing the reader by obscuring more important information. For example, the chart producer might have to decide whether to include a prominent landmark, the limit of controlled airspace, or a symbol indicating a parachute jump area. The problem of simplification has led directly to the use of aeronautical publications, such as the Airport/Facility Directory.

The Airport/Facility Directory is divided into seven booklets that cover the United States, including Puerto Rico and the Virgin Islands. Alaska is covered by the Alaska Supplement, and areas of the Pacific are covered by the Pacific Chart Supplement. These directories are a pilot’s manual containing data on airports, seaplane bases, heliports, navigational aids, communications, special notices, and operational procedures. They provide information that cannot be readily depicted on charts: airport hours of operation, types of fuel available, runway widths, lighting information, and other data. The directories are also a means of updating charts between chart issuances. Directories, charts, and other related publications may be obtained directly from NOAA. Free catalogs are available.

Classification is necessary in order to reduce the amount of information into a usable form. The cartographer must classify towns, rivers, and highways of different appearance on the ground into a common symbol for the chart. The pilot must then be able to interpret this information.

To maximize the amount of information on a chart, the cartographer uses symbols. Symbol shape, size, color, and pattern are used to convey specific information. The pilot must be able to interpret these symbols. Lack of chart symbol knowledge can lead to misinterpretation, confusion, and wandering into airspace where a pilot has no business.

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