Levelling:
The purpose of levelling is to determine the relative heights of points of interest on the surface of earth. Therefore, it includes measurements of distances in a vertical plane like distances in horizontal planes were measured in chain surveying. The levelling exercise will give an accurate network of elevations of ground surface covering the whole area of the project site. For several civil engineering projects, the levelling is of critical importance. For construction of highways, canals, pipelines of water, railway tracks, gas or sewage, dams etc., an accurate knowledge of associative heights of ground surface along its alignment and cross sectional details at appropriate intervals is essential for their execution. The primary design and project economy of such projects depend on the accuracy with that the levelling is carried out. A good network of levels gives an excellent idea of the existing terrain in terms of relative heights, based on that an engineer could plan, design and execute the project safely, efficiently and economically.
Objectives
After studying this unit, you should be able to
- know the basic principles of levelling and various terms used in leveling,
- elaborate the use and working of different types of levels and other instruments used in levelling,
- elaborate various operations and procedures performed during levelling exercise, and
- define various methods of contouring and uses of contour maps.