Quick Answer
Short Answer: To read ridgelines on a map, look for a series of contour lines that are closer together, often forming a series of "humps" or "ridges" in the terrain, indicating a ridge or a high point. Check the contour interval and scale to ensure accuracy. Use this information to orient yourself with the terrain.
Understanding Contour Intervals
Contour intervals are the vertical distance between each contour line on a map. A common interval is 20 feet, but it can vary depending on the map scale and intended use. For example, on a topographic map with a 1:24,000 scale, the contour interval is usually 40 feet. When reading ridgelines, look for areas where the contour lines are closer together, indicating a steeper slope. A general rule of thumb is that contours that are half the contour interval apart indicate a slope of about 20-30 degrees.
Identifying Ridgelines on the Map
To identify ridgelines on the map, look for a series of contour lines that are closer together, often forming a series of “humps” or “ridges” in the terrain. These lines may be parallel to each other, indicating a linear ridge, or may be irregular, indicating a more complex terrain feature. Check the map legend to determine the contour interval and use this information to estimate the steepness of the slope.
Visualizing Terrain Features
When reading ridgelines, it’s essential to visualize the terrain feature as a three-dimensional landscape. Imagine the contour lines as a series of hills or valleys, and use the contour interval to estimate the steepness of the slope. By combining this information with your knowledge of the surrounding terrain, you can develop a mental picture of the terrain and make more accurate decisions about navigation, route selection, and shelter placement.
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