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What information does a thicker contour line or index contour provide?

Thicker contour lines on a topographic map are called index contours and help to understand elevation data quickly. These lines play a critical role in helping you grasp the map's elevation data efficiently. Here's how:

Being Unique and Distinctive among Others: Index contours are visually emphasized by their increased thickness or use of a different color. This distinct appearance makes them easy to spot on the map, particularly beneficial when numerous contour lines are clustered together. This can be especially helpful when navigating in rugged terrain where precise elevation information is crucial.

Quick Overview of the Elevation: Unlike their thinner counterparts, index contours often have their elevation value explicitly labeled on the line itself. This eliminates the need to meticulously count elevation intervals between regular contour lines. This saves you valuable time and effort, especially when grappling with complex topographic maps.

Organized Pattern: Index contours typically follow a systematic pattern, appearing at regular intervals, such as every fifth or tenth contour line. This consistent organization provides a valuable framework for understanding the overall elevation range encompassed by the map. By quickly identifying the index contours, you can instantly grasp the map's elevation scale and how different areas compare in terms of height.

Thicker index contours serve as important landmarks on a topographic map. They stand out visually, have elevation labels, and are placed in an organized manner. All of these factors make it easier to interpret and analyze elevation data on the map. This, in turn, helps you make informed decisions about the terrain. Topographic maps can provide valuable information, whether you're planning a hike, analyzing weather patterns, or studying geological formations.

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