_______ are lines drawn on a map to locate, in the plan view, points of equal ground elevation.
Contours
Understanding Lines of Equal Ground Elevation on Maps
Mapping the Earth's surface involves representing three-dimensional features like hills, valleys, and flat areas on a two-dimensional plane, like a map. One crucial aspect of this is showing elevation, which is the height of a point above a reference level, usually mean sea level.
To depict elevation on maps, cartographers use various techniques. A common method is drawing lines that connect points of the same elevation. These lines provide a visual representation of the terrain's shape and slope.
What are Lines of Equal Ground Elevation?
The question asks for the specific term used for lines drawn on a map in a plan view that connect points of equal ground elevation. Let's examine the options provided:
- Profiles: A profile is a side view or cross-section of the terrain along a specific line. It shows the vertical shape of the ground, not lines connecting equal elevation points in a plan view.
- Contours: Contour lines are indeed lines drawn on a map connecting points of equal elevation. They are fundamental to representing topography (the shape and features of the Earth's surface) in a plan view. Closely spaced contours indicate steep slopes, while widely spaced contours indicate gentle slopes.
- Elevations: Elevation refers to the height of a single point above a reference datum. It's a value, not a line on a map connecting multiple points. Spot elevations are sometimes marked on maps with a value indicating the specific elevation at that point.
- Hatches: Hatches, or hachures, are short lines drawn on a map to indicate slopes. They typically point downhill and are denser on steeper slopes. While they show terrain form, they do not connect points of equal elevation.
Comparing the Options
Let's summarize the differences:
| Term | Description | Represents Equal Elevation Points? | Plan View? |
|---|---|---|---|
| Profiles | Side view/cross-section of terrain | No (shows elevation along a line) | No (side view) |
| Contours | Lines connecting points of equal elevation | Yes | Yes |
| Elevations | Height of a single point | No (a single value) | Yes (can be marked on a plan) |
| Hatches | Short lines indicating slope direction/steepness | No | Yes |
Based on the definitions and the comparison, the term that specifically refers to lines drawn on a map connecting points of equal ground elevation in a plan view is "Contours".
Conclusion on Equal Ground Elevation Lines
The lines drawn on a map to locate points of equal ground elevation in the plan view are known as Contours or Contour Lines. This method is standard practice in topographic mapping to visualize the shape of the land surface.
Revision Table: Key Mapping Terms
| Term | Meaning in Mapping |
|---|---|
| Contour Line | A line on a map connecting points of equal elevation. |
| Contour Interval | The vertical difference in elevation between adjacent contour lines. |
| Spot Elevation | The exact elevation of a specific point, often marked by a dot or cross with the elevation value. |
| Benchmark | A permanent marker placed on the ground at a point of known elevation. |
| Topography | The detailed mapping or charting of the features of an area, including hills, valleys, etc. |
Additional Information on Contours and Elevation Mapping
Contour lines provide a wealth of information about the terrain. Besides indicating equal elevation, their pattern reveals features like:
- Slope: The closer contour lines are, the steeper the slope; the farther apart, the gentler the slope.
- Hills and Ridges: These are shown by closed loops of contour lines. The highest point is inside the innermost loop.
- Valleys and Depressions: Valleys are indicated by V-shaped contours pointing uphill (towards higher elevation). Depressions are shown by closed contours with short lines (hachures) pointing inwards, indicating the ground slopes down into the depression.
- Saddles: A saddle is a dip or low point between two peaks, represented by contour lines that dip between two closed loops.
Understanding contour lines is essential for anyone interpreting topographic maps, whether for hiking, engineering, or environmental studies. They are the primary way that elevation is represented in a plan view on standard maps.
Important Questions from Contouring
Identify the correct statements.
i. Contour lines form sharp V-shaped curves across valley line, with the convex side of the curve towards the higher ground.
ii. Contour lines form U-shaped curves across valley line, with the convex side of the curve towards the higher ground.
iii. Contour lines form U-shaped curves across ridge line, with the concave side of the curve towards the higher ground.
iv. Contour lines form sharp U-shaped curves across ridge line, with the convex side of the curve towards the higher ground.
Two contour lines of same elevation:
The suitable contour interval for a map with scale 1:50,000 is
Contour lines cross a ridge or valley line at
Which of the following contour represents either hills or ponds?
