Contouring MCQ Quiz - Objective Question with Answer for Contouring - Download Free PDF

Explanation:

Contour maps are used for:

i. Calculating the water capacity of reservoirs.

ii. Determining the catchment area of the drainage basin

• Contours are the most accurate method of representing relief features.
• Contouring is an act of using contour lines when representing the relief of an area on the map.
• Contour lines are the lines drawn on the map connecting all points on the earth’s surface with equal elevations above a fixed datum line (usually the mean sea level).
  • They are numbered in either feet or meters, above sea level. Usually, these numbers represent the exact elevation of land above sea level for all points along that line.
  • Contour lines never cross or intersect each other.
  • The spacing or gap between the contour lines represents the degree of slope.
  • Contour lines lie perpendicular to streams and rivers.

Some of the salient uses of contours are described below

1. Nature of Ground

2. To Locate Route

3. Intervisibility between Stations

4. To Determine Catchment Area or Drainage Area

5. Storage capacity of a Reservoir

Explanation:

Contour Interval in a Contour Map

• Contour interval refers to the vertical distance between two consecutive contour lines on a map.

• Option 1 states that contour interval is inversely proportional to the scale of the map.

• This is correct because a map with a smaller scale covers a larger area, requiring larger contour intervals to prevent overcrowding of lines.

• Option 2 suggests that contour interval is directly proportional to the flatness of the ground.

• This is incorrect as flatter terrains may require smaller intervals for better detail.

• Option 3 mentions that contour interval is directly proportional to availability of the ground.

• This is not relevant to the concept of contour intervals.

• Option 4 states "All of the above," which is incorrect because only Option 1 is correct.

• Therefore, the correct answer is Option 1: Contour interval is inversely proportional to the scale of the map.

Explanation:

A Series of Closely Spaced Contour Lines Represents

• Contour lines on a map represent points of equal elevation above a reference level, such as sea level.

• When these contour lines are closely spaced, it indicates a rapid change in elevation over a small horizontal distance.

• This signifies a steep slope or a steep terrain, as the ground surface rises or falls sharply.

• In contrast, widely spaced contour lines represent a gentle slope, as the elevation changes gradually over a larger horizontal distance.

• The arrangement of these lines helps in understanding the topography of the land, which is essential for construction, navigation, and environmental studies.

• In this specific case, the correct answer is Option 1: Steep Slope, as closely spaced contour lines are characteristic of such terrain.

Explanation:

• Radial Line Method is most suitable for hilly and undulating terrains.

• In this method:

  • Contour levels are taken along radial lines (rays) from a centrally located station, typically a theodolite or plane table station.

  • Useful when the survey area is mountainous or inaccessible.

  • Observations are made by turning the table and sighting along different rays.

• This method helps in:

  • Accurate location of contour points

  • Efficient data collection in irregular or steep terrain

Explanation:

Closed Contours with Higher Values Inside

Closed contours on a map represent areas of equal elevation. When the values inside the contours are higher, it indicates that the elevation is increasing towards the center. This concept is essential in understanding the topography represented by contour maps:

• Contours with higher values inside represent elevated landforms like hills or mountains.

• Contours with lower values inside represent depressions or basins.

• Equal spacing between contours indicates a uniform slope.

• Irregular spacing indicates varying slopes, with closer contours showing steeper gradients.

Analyzing the Given Options

1. "Depression" (Incorrect)

   • Depressions are represented by closed contours with lower values inside, not higher values.

   • Thus, this option does not match the given condition.

2. "Hill" (Correct)

   • Hills or elevated landforms are represented by closed contours with increasing values towards the center.

   • This matches the given condition perfectly, making it the correct answer.

3. "Plain Surface" (Incorrect)

   • Plain surfaces are represented by widely spaced or absent contours, not closed contours with higher values.

   • Hence, this option does not match the given condition.

4. "None of the Above" (Incorrect)

   • Since "Hill" is the correct answer, this option is not valid.

   • This option does not apply to the given condition.

Final Answer: Option 2 - Hill

The different types of area measuring devices are as follows:

1. Clinometer or Inclinometer: It is used to measure angles of slopes either elevation or depression of an object with respect to gravity direction as reference.

2. Planimeter: It is the mechanical device used to measure area of plane. This measurement consists of dragging along boundary region.

Concept:

Contour Interval = 25/(No. of cm per km) (metres)

Also Contour Interval = 50/(No. of inches per mile) (feet)

Calculation:

For the scale of 1: 10000.

1 cm represents 10000 cm

∴ 1 cm represents 10000 × 10-5 km = 0.1 km

∴ 1 cm represents 0.1 km. So 1 km represent 10 cm

∴ Contour interval = 25/10 = 2.5 meters

Hence, the most appropriate answer is option 1.

Explanation:

Indirect Method of Contouring:

• Indirect methods are quicker, cheaper, and less laborious than the direct method
• In this method, a series of guide points are selected along with a system of straight lines and their elevations are determined
• These points are then plotted, and contours are drawn by interpolation

Three methods used for interpolation are as follows:

(i) By Estimation:

This is a rough method and is used on a small-scale map.

(ii) By Arithmetic Calculations

This is a very accurate method but a tedious one. The position of contours points between guide points is located by arithmetic calculations.

(iii) By Graphical Method

This is a rapid and convenient method and gives higher accuracy than the estimation method. It involves a lot of interpolation work.

Important points:

Arithmetical Calculation is considered more accurate than a graphical method, as the graphical method assumes only linear variation between the two guide points.

The geometric method is not used for interpolation of contours.

Explanation:

Horizontal Equivalent: 

(i) The horizontal distance between two points on two consecutive contour lines for a given slope is known as horizontal equivalent.

(ii) For a given contour interval, scale of the map and the nature of terrain decide the horizontal equivalent. As the slope becomes more and more steeper, the horizontal equivalent decreases.

Additional Information

Contour elevation:

(i) It is the line joining points of equal elevation on the surface of the earth.

Contour Interval: 

(i) The difference in elevation between successive contour lines on a given map is fixed. This vertical distance between any two contour lines on a map is called the contour interval.

Explanation:

Different characteristics of contours are as follows:

From the above observation:

Explanation:

Different methods of contouring are:

Tachometric method of contouring

• This method is used for angular surveying.
• This method is best suited for hilly terrains as the number of stations which can be commanded by a tachometer is far more than those by a level and thus the number of instrument settings is considerably reduced.

Direct Method

• The reduced level of different selected points is located and joined to form a contour.
• This method is accurate but very tedious and slow.

Square method or grid method

• In this method, we draw a grid point on the ground and measure the reduce level of all these points.
• It is generally used in plain terrain.

Cross Section method

• This method is generally used for hilly terrain to produce contour lines.

Explanation:

Contour is defined as an imaginary line on the ground surface joining the points of equal elevation.

Contours show distinct characteristic features of the terrain as follows:

1. Contour lines cross a watershed or ridgeline at right angles
2. No two contour lines can meet or cross each other except in the rare case of an overhanging or vertical cliff or wall
3. The direction of the steepest slope is along with the shortest distance between the contours.
4. In the direct method of contouring, the contours are not interpolated.
5. Closely spaced contour lines indicate a steep slope.
6. Widely spaced contour lines indicate a gentle slope.
7. Equally spaced contour lines indicate a uniform slope.
8. Closed contour lines with higher elevation towards the center indicate hills.
9. Closed contour lines with reducing levels towards the center indicate pond or other depression.
10. Contour lines of ridge show higher elevation within the loop of the contours. Contour lines cross the ridge at right angles.
11. Contour lines of the valley show reducing elevation within the loop of the contours. Contour lines cross the valley at right angles.
12. All contour lines must close either within the map boundary or outside.
13. All points on a contour line are of the same elevation.

Contour lines are the lines joining the points of equal elevation on the ground surface.

Characteristics of the contour lines are:

1. Two contour lines of different elevation cannot cross each other.

2. Contour lines of different elevations can unite to form one line only in case of a vertical cliff.

3. Contours lines crosses a valley or ridge line at 90°.

Concept:

Contour Map:

• From a contour map, the nature of the ground surface of an area can be known. So for identifying a suitable site for a dam or reservoir and for marking the tentative alignment of engineering projects involving roads, railways, etc. a contour map is essential.
• The horizontal scale is used to plot a contour map.

Contouring:

• Contours are the most accurate method of representing relief features.
• Contouring is the act of using contour lines when representing the relief of an area on the map.
• Contour lines are the lines drawn on the map connecting all points on the earth’s surface with equal elevations above a fixed datum line (usually the mean sea level).
  • They are numbered in either feet or meters, above sea level. Usually, these numbers represent the exact elevation of land above sea level for all points along that line.
  • Contour lines never cross or intersect each other.
  • The spacing or gap between the contour lines represents the degree of slope.
  • Contour lines lie perpendicular to streams and rivers.

Some of the salient uses of contours are described below

1. Nature of Ground

2. To Locate Route

3. Intervisibility between Stations

4. To Determine Catchment Area or Drainage Area

5. Storage capacity of a Reservoir

Explanation:

Depression:

A set of close contours with lower figures inside and higher figures outside indicates depression.

Given data:

The values from point A to point B are 500 m, 400 m, 300 m, 200 m, 200 m, 300 m, 400 m, and 500 m.

Additional Information

Hill: 

• A set of close contours with higher figures inside and lower figures outside indicates a hill.

Cliff:

• Cliffs are the steep rock faces along the sea coast and may be vertical where the contour line coincide with each other, an overhanging cliff where the contour lines intersect each other.