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Difficulty: MediumCross-Sections and Intervisibility

Assuming an absence of surface obstructions such as trees or tall structures, two observation stations located respectively at the summit and the base of a hill possessing a convex slope are intervisible.

Answer: Answer

Answer

False. Two points located at the summit and the base of a convex slope are not intervisible because the outward bulge of the slope in its upper-middle section obstructs the direct line of sight.
Intervisibility between two points on a map depends on whether the relief between them drops below the straight line of sight. On a convex slope, the upper portion has a gentle gradient (contours far apart) while the lower portion is steep (contours close together). This creates a bulging profile where the central terrain rises into the direct sightline between the summit and the valley floor, preventing mutual visibility.

Step-by-Step Solution

1
Analyze the characteristic contour arrangement and profile of a convex slope.
On a convex slope, contours are widely spaced near the crest (gentle gradient) and closely spaced near the base (steep gradient).
Understanding the physical shape of the land profile is necessary to evaluate the path of the sightline.
2
Evaluate the line of sight between the highest point (summit) and lowest point (base).
The direct line connecting the summit and base passes below the bulging middle section of the hill profile.
Intervisibility requires that no ground point along the cross-section intersects or rises above the straight line connecting the two stations.
3
Determine intervisibility status.
The stations are not intervisible.
Intervening high ground caused by the convex curvature blocks the sightline.

Key Concept

Intervisibility on Convex vs. Concave Slopes
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Topics

Cross-Sections and Intervisibility

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