What term describes a line that connects points of equal value on a map?

The term "isoline" refers to a line on a map that connects points of equal value for a particular variable, such as elevation, temperature, or precipitation. Isolines are essential in geography and cartography for visualizing spatial patterns and variations across a landscape. For example, in a topographic map, contour lines are specific types of isolines that represent elevation and connect points of equal height above a reference datum.

The broader category of isolines includes various specific types, such as contour lines (specifically for elevation), isotherms (for temperature), and isohyets (for precipitation). This flexibility allows the term to encompass any line that conveys equal value for any measured parameter.

Other options provided relate to different concepts. Contour lines are indeed a type of isoline but are narrower in definition to only elevation. Pathlines refer to the paths that particles take over time, which is distinct from representing constant values on a map. Gradation line is not a standard term in this context and does not specifically relate to the connection of points with equal value. Understanding the broader classification that "isoline" represents helps clarify its significance in mapping and data representation.