Map Use - Scale
Scale is a fairly straight forward item. A globe is a scale model of the earth. If the earth is 12,800 km in radius and the globe is 30 cm (12 inches), then the scale is
s = (30cm/(100 cm/m * 1000 m/km ) / 12,800 km
or roughly
s = 1 / 42,700,000
s = 1 : 42,700,000
The second form with the colon in place of the division bar is common on maps.
The common map legend gives the scale as 1:24,000 often read as one to twenty four thousand. This is common in the US where it means 1 inch is 2000 feet.
Notice that scale values are really a small numbers. That is one reason they are represented as a ratio. But the divisor is big. So a 1:12,000 (one to twelve thousand) is a Larger Scale map than a 1:50,000 (one to fifty thousand). Because maps are generally about the same size, a small scale map (say 1:5,000,000 one to five million) will cover a large area. Conversely a large scale map (1:24:000) will cover a smaller area. This potential confusion is why this module has referred to small area maps rather than large scale maps.
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