Which contour type is heavier and used as the primary elevation reference on older maps?

Which contour type is heavier and used as the primary elevation reference on older maps?

• A. Index Contour Lines
• B. Intermediate Contour Lines
• C. Supplementary Contour Lines
• D. Contour Lines

Answer: (A)

On topographic maps, the heavy, prominent lines are the index contour lines. These bold lines, usually labeled with their exact elevation (often every fifth contour), serve as the primary reference for reading elevation quickly. They stand out to give you a quick sense of the terrain’s height without having to read every single contour line, which is especially useful on older maps where fewer labels are present. The lighter intermediate contours fill in the elevations between index lines to show precise slope, while supplementary contours (when used) are faint lines added in areas needing extra detail. So the heavier, labeled lines used as the main elevation reference are the index contour lines.

On topographic maps, the heavy, prominent lines are the index contour lines. These bold lines, usually labeled with their exact elevation (often every fifth contour), serve as the primary reference for reading elevation quickly. They stand out to give you a quick sense of the terrain’s height without having to read every single contour line, which is especially useful on older maps where fewer labels are present. The lighter intermediate contours fill in the elevations between index lines to show precise slope, while supplementary contours (when used) are faint lines added in areas needing extra detail. So the heavier, labeled lines used as the main elevation reference are the index contour lines.