Finding the highest elevation on a contour map involves identifying specific features and understanding the map's key. The highest point, often a peak or summit, is usually located within the smallest, innermost closed contour line, or marked explicitly as a spot elevation.
Understanding Contour Map Basics
Before locating the highest point, it's crucial to understand the fundamental elements of a contour map:
| Feature | Description |
|---|---|
| Contour Lines | Lines connecting points of equal elevation. |
| Contour Interval | The vertical distance in elevation between adjacent contour lines. This is usually stated on the map's legend. |
| Index Contours | Thicker, labeled contour lines that typically occur every fifth contour, making it easier to read elevations. |
| Spot Elevations | Specific points marked with an 'X' or a small dot, accompanied by an exact elevation number. These are the most precise indicators of elevation. |
| Closed Loops | Contour lines that form a complete circle, indicating a hill, peak, or depression. Tighter loops indicate steeper terrain. |
Step-by-Step Guide to Locate the Highest Elevation
Follow these steps to pinpoint the highest elevation on your contour map:
- Identify the Contour Interval: Locate the contour interval in the map's legend. This value (e.g., 20 feet, 10 meters) tells you the change in elevation between each standard contour line.
- Look for Spot Elevations: Scan the map for any "X" marks or small dots with a number next to them. These are spot elevations and represent precise measurements of peaks, benchmarks, or other significant points. If a spot elevation is present within a closed contour, it's typically the highest point in that immediate area.
- Find the Innermost Closed Contour: If no spot elevation is explicitly marked for a peak, look for the smallest, tightest closed contour line. This innermost loop indicates the summit of a hill or mountain.
- Determine the Elevation Range:
- Once you've found the innermost closed contour, identify its elevation. This is usually done by tracing it back to an index contour (a thicker, labeled line) or by counting up from a known elevation using the contour interval.
- The actual highest point will be above the elevation of this innermost closed contour line.
- It will be below the elevation of the next contour line that would appear if the peak were slightly higher, based on the contour interval.
- Calculate the Highest Possible Elevation: To determine the highest possible elevation, consider the contour interval and the highest visible closed contour.
- For example, if the highest visible closed contour line is 290 meters and the contour interval is 10 meters, the peak's true elevation is greater than 290 meters but less than the next contour line, which would be 300 meters (290 + 10).
- Therefore, the highest possible integer elevation for the peak would be 299 meters, as it hasn't reached the 300-meter contour line.
Practical Tips for Accuracy
- Follow Index Contours: Use the bolded index contours to quickly grasp the general elevation and direction of slopes.
- Contour Line Rules: Remember that contour lines never cross (except in the rare case of an overhanging cliff, which would be specially marked), and they always enclose.
- Depressions vs. Peaks: Closed contour lines with hachure marks (small tick marks pointing inward) indicate a depression, not a peak.
By carefully examining the map's features and understanding the relationship between contour lines and the contour interval, you can accurately determine the highest elevation.
