Most travel, street, or highway maps show a measurement scale, usually in terms of miles and kilometers. To determine a straight line (horizontal) distance on a map, take a piece of paper and mark the origin and destination as tick marks on the paper. Then measure the “distance” between the tick marks based on the map scale to find the distance in miles or kilometers.

Topological maps also have scales, but in this case the scale is a ratio representing the measure on a map to some number of the actual units of measure on the Earth’s surface. For example, a map with a scale of 1:25,000 means that one inch on the map is equal to 25,000 inches on the ground. Because both numbers have the same units, it can also be interpreted as any unit measure. For example, the same map could also be interpreted as 1 centimeter equals 25,000 centimeters on the ground, or 1 meter equals 25,000 meters, and so on. For those who prefer to measure in miles and kilometers, most topographic maps also offer a graphic scale in the legend. (For more about scales, see “Math in Engineering.”)