[Ref FAA-H-8083-18 Flight Navigator Handbook]
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.
Charts are made to various scales for different purposes. If a chart is to show the whole world and yet not be too large, it must be drawn to small scale. If a chart is to show much detail, it must be drawn to a large scale
large area, small scale; small area, large scale
the smaller the denominator of the representative fraction, the larger the scale – examples: WAC 1:1,000,000 ; VTC 1:500,000
On aeronautical charts, the scale is indicated in one of two ways:
- representative fraction
- This means one of any unit on the chart represents 500,000 of the same unit on the earth.
- graphic scale
- could shown by a “graduated line” – usually is found printed along the border of a chart