In which type of mapping are lines of equal value drawn, known as contour lines?

Contour lines, which represent lines of equal value, are a central feature of isopleth maps. This type of mapping is specifically designed to depict phenomena that vary over a geographical area and can include elements like elevation, temperature, or rainfall. The isopleth map connects points of equal data values, enabling users to visualize gradients and changes across the mapped space effectively.

In contrast, choropleth maps use different shades or colors within predefined geographic areas (like states or counties) to show distinct values or categories of data but do not involve the direct representation of continuous data through connecting lines. Thematic maps encompass a broader category that highlights specific themes or subjects but can utilize various methods of representation, not solely reliant on equal value lines. Proportional symbol maps represent data using symbols of varying sizes to indicate magnitude, focusing on the point data rather than the continuous nature of values found in isopleth mapping.

This distinction illustrates why isopleth maps are uniquely equipped to effectively represent values through the use of contour lines, making them essential for visualizing and analyzing spatial data trends.