What defines a "grid zone" on a map?

A "grid zone" on a map specifically refers to one of the 60 north-south divisions of the Earth's surface. Each grid zone is defined by lines of longitude and latitude, which allow for more accurate navigation and mapping. These divisions help to standardize the way that locations are identified on maps, making it easier for users to pinpoint exact coordinates and navigate effectively.

In the context of topographical and military mapping, each grid zone assists in organizing the vast expanses of the Earth's surface into manageable sections, ensuring that coordinates are clear and easily interpretable. This is crucial for operations that require precise location data, such as military strategies, navigation, and surveying.

Knowing that the other options describe different concepts helps clarify how grid zones specifically pertain to the organization of geographical areas rather than terrain types, elevation references, or generic map features.