Contour Surveying and Its Importance

Contour Surveying is the branch of surveying that uses contour lines to determine variations in the elevation of the earth's surface and relative positions.

The process of determining contour lines in the ground or earth's surface is known as contouring, and the map produced by this contouring process is known as a contour map.

The purpose of contour surveying is to determine the altitude or height of any surface.

Application of Contour Surveying in Civil Engineering

Contour surveying is useful in civil engineering in the following areas:

1. In the proper and precise placement of engineering projects such as roads, canals, etc.
2. Determining the location of water supply, water distribution, and resolving the problem of steam pollution.
3. Dams, reservoirs, aqueducts, transmission lines, and other structures are being planned and built.
4. In the location of new industrial plants.
5. To determine the indivisibility of stations.
6. To determine the profile of the country in any direction.
7. Calculate the amount of soil that will be cut and filled and the reservoir capacity.

 

 

Contour Line

A contour line, also known as a 'contour line,' is an imaginary line that passes through points of equal elevation on the death surface. It is also known as the intersection of the level surface at a specific ground level.

As a result, each contour line has its own altitude in relation to the assumed ground surface.

Read More

>Calculation of unit weight of steel bars in per meter and Its Formulas

>5 Methods for Plotting a Traverse Survey | Compass Surveying | Surveying

>Quantity Surveyor and Responsibilities of QA/AC Engineer

Characteristics of Contour lines

1. All points on a contour line have the same elevation in contour surveying.
2. In a flat region, contour lines are far apart; contour lines are close together in a mountainous region.
3. A Uniform slope is represented by a uniformly spaced contour line from each other. In contrast, flat ground is represented by a straight line that is uniformly spaced and parallel to each other.
4. A hill and the higher value inside indicated a series of contour lines close to each other.
5. A series of closed contour lines indicate depression if the higher value is outside.
6. In the valley or ridge portion, contour lines are at right angles. If the higher value is inside the bend, it denotes 'Ridge,' and if it is outside the bend, it denotes 'Valley.'
7. Contour lines can only end close to themselves or outside the map limit.
8. Whether there is an overhanging cliff or not, contour lines do not cross.
9. Unless there is a vertical cliff, contour lines never intersect.
10. A saddle is a depression between two peaks. Four sets of contours are shown here. It denotes the intersection of two ridges or a dip in a ridge. The watershed line is the line that runs through saddles.

 The contour line cannot be broken; it must be continuous. A contour line comprises the same points, so all of the same points can be found in a single contour line.

We can easily access the earth's surface altitudes from here. It also generates a plan for that specific portion. As a result, the contour map serves as both a plan and a section of that area.

Contour Interval

The contour interval is the constant vertical distance between any two consecutive contours.

We should use a map with a constant contour interval. The variable contour interval gives an incorrect impression of the surface's relative steepness in different parts of the map.

Horizontal equivalent refers to the horizontal distance between two adjacent contours. It is determined by the slope of the ground.

Factors affecting the selection of Contour Interval

There are various factors in contour surveying on which the selection of the appropriate contour interval depends. They are-

Nature of Ground The contour interval is small in countries with flat and uniformly sloping terrain. In contrast, the contour intervals are large in countries with hilly terrain. The contours will be too close if it is too small.

Purpose of the survey: When the area to be surveyed is small, the contour interval is also small, for example, when determining earthwork, etc. Compared to less important works, large intervals are used in large areas.

The scale of the map: The contour interval should be proportional to the scale, i.e., the smaller the scale, the greater the interval ratio.

Funds available: The greater the amount of work, the lower the contour interval.