Scale and distance
The idea
Map scale relates map distance to ground distance. Use the units and scale supplied by the map rather than guessing from visual size. A printed map’s scale can become inaccurate when an image is resized, unless the scale bar changes with it.
Worked example
At a scale of 1 centimeter to 2 kilometers, a 3-centimeter map distance represents 6 kilometers in a straight line. A road route may be longer because it bends.
Another application
At 1 cm = 5 km, a 2.5 cm separation represents 12.5 km. If an image is doubled in size without adjusting the printed ratio, a ruler reading cannot be interpreted using the old ratio.
A common misunderstanding
Map distance is not always travel distance. Curving roads and barriers can make the route longer than the straight-line separation.
Try it yourself
Make a map of a room with a stated scale. Measure two real distances and check that the drawn distances match.
Check your understanding
At 1 cm = 5 km, what does 4 cm represent?
Reveal the explained answer
20 km, assuming the map has not been resized relative to its scale.