What type of line is used to indicate equal elevation on a map?

The type of line used to indicate equal elevation on a map is known as a contour line. These lines connect points of the same elevation, allowing users to visualize the terrain's features and understand the changes in elevation across an area. Contour lines are essential in topographic maps, where they depict the relief of the land, showing hills, valleys, and slopes.

Contour lines can provide valuable information about the steepness of terrain—closely spaced lines indicate steep slopes, while lines that are farther apart suggest gentle slopes. Additionally, contour lines may form closed loops that signify hilltops or depressions. This clarity in representing elevation change enables effective analysis and decision-making in various applications, such as planning, environmental studies, and outdoor navigation.

The other options do not represent equal elevation in the same way as contour lines do. Vector lines are used to represent direction and magnitude in spatial analysis, isolines are a broader category that can include various types of lines representing other variables like temperature or precipitation, and demarcation lines refer to boundaries in a more general sense, not specifically related to elevation.