On a topographic or engineering map, what do the drawn lines that connect points of equal ground elevation represent? Choose the correct term for these elevation-reference lines shown in plan view.

Introduction / Context:
Site design, drainage analysis, and grading plans depend on understanding ground shape. Maps use specific linework to express how elevation changes across the landscape in plan view, enabling quick visualization of slopes, ridges, and depressions.

Given Data / Assumptions:

• We are viewing a plan (overhead) map.
• Lines connect points that share the same elevation value.
• We must name those lines correctly.

Concept / Approach:

Contour lines (or contours) are continuous lines on a map joining locations of equal elevation relative to a datum. Evenly spaced contours indicate uniform slopes; closely spaced ones indicate steep terrain; widely spaced ones indicate gentle slopes. Index contours are labeled to help read elevations quickly.

Step-by-Step Solution:

Verification / Alternative check:

Civil engineering references emphasize contours for preliminary design, earthwork estimation, and hydrologic analysis. Profiles and cross-sections are derived from contours to study elevation changes along a path.

Why Other Options Are Wrong:

Elevations: scalar values at single points, not the lines connecting equal values.

Profiles: vertical sections along a chosen baseline (e.g., road centerline), not plan-view elevation lines.

Hatchures: unrelated term here; hachures are an older shading method to represent relief, not equal-elevation lines.

Common Pitfalls:

Misreading closed contour loops that indicate hills (higher inside) or depressions (lower inside, sometimes marked with ticks). Always check labeled index contours.

Final Answer:

Contours