Identify the correct characteristic of the scale used when drawing a profile of ground from profile levelling data.
Correct Answer: D. Vertical distances are exaggerated
📚 Detailed Explanation: Vertical Scale Is Exaggerated in Profile Levelling Drawings
Why D (Vertical distances are exaggerated) is correct: Profile levelling records the elevation of ground at regular horizontal intervals along a route. When the longitudinal section is plotted, the vertical scale is made much larger than the horizontal scale. Without this exaggeration, minor undulations in the ground — which critically affect design of roads, canals, and pipelines — would be invisible at the horizontal scale used.
Why Vertical Scale is Exaggerated
| Reason | Explanation |
|---|---|
| Terrain relief is subtle | A road alignment over 5 km may vary only 20–30 m in height. At 1:5000 horizontal scale, 20 m height = just 4 mm on paper — invisible |
| Design precision needed | Engineers must clearly see rises, falls, and grades for earthwork calculations; exaggerated vertical scale reveals these |
| Typical ratio | Horizontal 1:1000 to 1:5000; Vertical 1:100 to 1:500 — vertical exaggerated by factor 5–20× |
Why Other Options Are Wrong
| Option | Why Incorrect |
|---|---|
| A. Horizontal exaggerated | Opposite; horizontal is NOT exaggerated |
| B. Both at 1:1 scale | Never used; 1:1 would require enormous paper for any reasonable survey distance |
| C. Both at same scale | Same as B; profile plots always have different H and V scales |
| D. Vertical exaggerated | Correct — standard practice for all longitudinal profile plots |
- In profile levelling plots, the vertical scale is exaggerated relative to horizontal scale.
- This makes minor elevation changes visible at engineering drawing scale.
- Typical: H scale 1:2000, V scale 1:200 (V exaggerated 10×).