Which of the following is NOT a type of contour line?

Contour lines are essential elements on topographic maps, representing elevation changes across the landscape. Each type of contour line serves a specific purpose in conveying information about the terrain.

Index contour lines are the thicker, often darker lines typically labeled with elevation values. They are spaced at regular intervals and provide a clear reference for understanding the elevation changes across the map.

Intermediate contour lines are the thinner lines found between index contours. They help indicate more subtle changes in elevation that the index lines do not cover, thereby allowing for a more detailed understanding of the terrain.

Supplementary contour lines are also present on some maps, and while they may vary in application, they usually represent minor changes or additional detail that complements the information given by the primary contour lines.

The term "relative contour lines" does not correspond to a recognized concept in land navigation or topographic mapping. Therefore, it does not exist within the established types of contour lines used in mapping. This makes it the correct answer in identifying the type that is NOT used. Understanding the different types of contour lines—index, intermediate, and supplementary—clarifies how they contribute to reading and interpreting terrain features accurately.