<P> The scale of a map is the ratio of a distance on the map to the corresponding distance on the ground . This simple concept is complicated by the curvature of the Earth's surface, which forces scale to vary across a map . Because of this variation, the concept of scale becomes meaningful in two distinct ways . The first way is the ratio of the size of the generating globe to the size of the Earth . The generating globe is a conceptual model to which the Earth is shrunk and from which the map is projected . </P> <P> The ratio of the Earth's size to the generating globe's size is called the nominal scale (= principal scale = representative fraction). Many maps state the nominal scale and may even display a bar scale (sometimes merely called a' scale') to represent it . The second distinct concept of scale applies to the variation in scale across a map . It is the ratio of the mapped point's scale to the nominal scale . In this case' scale' means the scale factor (= point scale = particular scale). </P>

What does the scale of a map show