Appendix C Navigational Charts

APPENDIX C

NAVIGATIONAL CHARTS

C100. INTRODUCTION

An aeronautical chart is a pictorial representation of a portion of the earth's surface upon which

lines and symbols in a variety of colors represent features that can be seen. In addition to ground

images, many additional symbols and notes are added to indicate additional information

necessary for navigation. Aeronautical charts are vital aids to navigation. Because of their great

importance, you must be thoroughly familiar with the wide variety of aeronautical charts

available to you and their proper use.

Scale. The ratio between any given unit of length on a chart and the true distance it represents

on the earth is the scale of the chart. The scale may be relatively uniform over the whole chart,

or it may vary greatly from one part of the chart to another. The charts you will use will

normally have a uniform scale. Charts are made to various scales for different purposes. If a

chart shows the whole world, it is drawn to a small scale; otherwise it would be too big to be

useful. If a chart needs to show a lot of detail, it needs to be drawn to a large scale. Remember:

"Large area=small scale and small area=large scale" (Figure C-1). The scale of a chart may be

given by a simple statement, such as, "1 inch equals 10 miles." This means 10 miles on the

earth's surface is shown as 1 inch on the chart. On aeronautical charts the scale is indicated as a

representative fraction or graphic scale.

Representative Fraction. The scale may be given as a representative fraction, such as

1:500,000. This means that one of any unit on the chart represents 500,000 of the same unit on

the earth. For example, 1 inch on the chart represents 500,000 inches on the earth. A

representative fraction can be converted into a statement of mile to the inch. Thus, if the scale is

1:1,000,000, 1 inch on the chart stands for 1,000,000 inches or about 68.5 NM. Similarly, if the

scale is 1:500,000, 1 inch on the chart represents about 13.7 NM. Thus, the larger the

denominator of the representative fraction, the smaller the scale.

NAVIGATIONAL CHARTS C-1