Which of the following is NOT a purpose of a flow-line map?

A flow-line map is specifically designed to visualize the movement of items, whether that be goods, people, or ideas, typically represented by lines of varying thickness to denote the volume or intensity of that flow. This makes it particularly effective for representing the flow of goods, illustrating migration patterns, and displaying trends in population movement, as these types of information inherently involve directional movement across geography.

In contrast, showing geographic elevations pertains to a topographic representation, which involves contour lines that illustrate the physical heights and depressions of a terrain. This purpose is fundamentally different from what a flow-line map is used for. Therefore, the characteristic of showing geographic elevations does not fit within the intended uses of a flow-line map.