Shape Versus Size – Conformality Versus Equivalency
Each of the map projections previously discussed as well as any other type of map projection must consider two important factors. What is more important, depicting the accurate sizes of objects on the map, or depicting accurate shapes of these objects? The challenge is that you cannot have both. The more accurately you depict shape, the less accurate will be your depiction of size, and vice versa.
A map which portrays shape accurately is called a conformal map. Conformal maps are useful in that they help us understand the true shape of the items on the map. However, these maps have many drawbacks. A conformal map tends to get quite distorted, especially towards the top and bottom of the map. This creates problems with scale. The scale may be accurate near the equator, but the further one travels form the equator, the less accurate the scale becomes.
A map which portrays size accurately is referred to as an equivalent map. Equivalent maps are very useful. They accurately show the size of objects on the map. This means that no matter what part of the map we examine, the scale will remain accurate. However, equivalent maps also have drawbacks. Primarily the shape of objects is distorted.