Direct Method of Contouring

Introduction
Contouring is the process of determining and representing the shape and elevation of the land surface. It is an important aspect of surveying, which is used in various applications such as mapping, engineering design, and construction. There are several methods of contouring, including the direct method, the map method, and the digitizing method. In this article, we will focus on the direct method of contouring.

Overview of Direct Method
The direct method of contouring involves locating and marking the contour lines on the ground using a level and a graduated staff. The method is based on the principle that points lying on the same contour line have the same elevation. The direct method is considered as the most accurate method of contouring, and it is suitable for all types of terrain, including hilly terrains.

Procedure for Direct Method
The following are the steps involved in the direct method of contouring:

1. Set up the level: The first step is to set up the level at a convenient location where the entire survey area can be observed.

2. Establish the benchmark: A benchmark is a point of known elevation, which is used as a reference point for the survey. The benchmark can be established by using a permanent object such as a building or a tree, or by driving a stake into the ground.

3. Take readings: The level is then used to take readings on the graduated staff at various points on the survey area. The readings are taken at regular intervals, such as every 10 meters or every 20 meters.

4. Calculate elevations: The elevations of the points are calculated by subtracting the reading on the staff from the height of the level instrument at the time of taking the reading.

5. Plot the contour lines: The contour lines are then plotted on the ground by joining the points of equal elevation. The contour lines can be either hand-drawn or digitized using computer software.

Advantages of Direct Method
The following are the advantages of the direct method of contouring:

1. Most accurate method: The direct method is considered as the most accurate method of contouring, as it involves measuring the elevation of each point on the ground.

2. Suitable for all terrains: The direct method is suitable for all types of terrain, including hilly terrains.

3. Quick method: The direct method is a relatively quick method of contouring, as it does not require any complex calculations.

Conclusion
In conclusion, the direct method of contouring is a highly accurate method that is suitable for all types of terrain. It involves locating and marking the contour lines on the ground using a level and a graduated staff. The method is relatively quick and does not require any complex calculations.