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What is Contour? | What is Contour Contour Interval | Definition, Purpose and Factors Affecting of Contour | Contour in Surveying

Today we discuss all related What is Contour?, Contour Interval, Definition, Purpose and Factors Affecting Selecting of Contour Interval

Contour in Surveying

What is Contour?

Definition of contour: A contour is a line joining points of equal elevation on the ground. All the points lying on a contour will have equal elevation.

Second Definition: Contour is an imaginary line joining points of equal elevation.

e.g. A contour of 60.00m indicates that all points lying on this contour are having an elevation of 60 m.

What is Contour? | What is Contour Contour Interval | Definition, Purpose and Factors Affecting of Contour

What is a Contour Interval

Contour Interval Definition

Contour interval is defined as verticle distance between any two consecutive Contours. or It is the difference of elevations between two successive contours.

The contour interval is kept constant for the contour plan. otherwise, the general appearance of the map will be misleading.

Necessity of Contour Plotting

Plotting of contours gives the topography of the area surveyed.

It gives a general idea about the topographic features of the ground which is helpful in deciding the location or alignment of an infrastructure project.

Characteristics of Contour

  • A series of contour lines with higher values inside indicate a hill
  • A series of counter lines with lower values inside the loop always indicate depression
  • Close contour lines indicate a steep slope
  • Wide contour lines indicate a flatter slope
  • Contour lines never cross each other except in the case of an overhanging cliffs.
  • All points on a contour line have equal elevation

Factors Affecting Selecting of Contour Interval

The choice of proper contour interval depends upon the following considerations or factors affecting selecting of the Contour interval is given below:

Nature of The Ground

Contour interval varies with the topography of the area.

It is large for steep grounds and small for flat grounds.

Scale of The Map

The contour interval should be inversely proportional to the scale.

If the scale is small the contour interval should be large.

If the scale is large, the contour interval should be small.

Also Read: Something About Civil Engineering Design Software

Purpose an Extent of The Survey

The contour interval largely depends upon the purpose and the extent of the survey. 

For example, if the survey is intended for detailed design work or for accurate earthwork calculations, a small contour interval is to be used.

The extent of the survey in such cases will generally be small in the case of location survey, for a line of communications and for reservoir and drainage areas, where the extent of the survey is large, a large contour interval is to be used.

Time

If the time available is less, a greater contour interval should be used.

If the contour interval is small, greater time Will be take in the field survey, in reduction and in plotting the map.

Funds

The contour interval is kept large When funds are limited and the contour interval is kept small when a fund is not a problem.

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Also ReadPlane Table Survey | Equipment, Advantages and Limitations of Plane Table Survey

If you want to learn more and detailed learning then download below NCERT book on Topographical Maps

FAQ 1: What is Contour?

Definition of contour: A contour is a line joining points of equal elevation on the ground. All the points lying on a contour will have equal elevation. Second Definition: Contour is an imaginary line joining points of equal elevation.

FAQ 2: What is a Contour Interval?

Contour interval is defined as verticle distance between any two consecutive Contours. or It is the difference of elevations between two successive contours.

FAQ 3: What are the Factors Affecting Selecting of Contour Interval?

1. Nature of The Ground Contour interval varies with the topography of the area. It is large for steep grounds and small for flat grounds. 2. Scale of The Map The contour interval should be inversely proportional to the scale.

FAQ 4: What are the Purpose an Extent of The Survey?

1. Time If the time available is less, a greater contour interval should be used. If the contour interval is small, greater time Will be take in the field survey, in reduction and in plotting the map. 2. Funds The contour interval is kept large When funds are limited and the contour interval is kept small when a fund is not a problem.

FAQ 5: What are the Characteristics of Contour?

1. A series of contour lines with higher values inside indicate a hill 2. A series of counter lines with lower values inside the loop always indicate depression 3. Close contour lines indicate a steep slope 4. Wide contour lines indicate a flatter slope 5. Contour lines never cross each other except in the case of an overhanging cliffs. 6. All points on a contour line have equal elevation

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