"Contouring" theory note based on ioe syllabus 4 th semester surveying

•              COUNTOURING

Introduction :

Contouring:

The process of plotting contours in a plan or map is known contouring. The main objective of contouring is to obtain the point on the ground having same RL. It gives the topographical feature of the ground. It depends on the instrument used to determine the horizontal and vertical position of points. 

Following are the two field method of contouring :

(1)Direct Method :In the direct method,the contour to be plotted is actually traced on the ground. In this method, the equal elevated points are joined. This method is preferred for large scale maps, small contour interval. It is slow and tedious method. 

(2)Indirect Method:In this method, the R. L of different points are taken at regular intervals along a series of lines setup on the ground. The position of the points are plotted on a sheet to any suitable scale.The spot levels are noted at the respective points. Elevation of desired contour are interpolated in between spit levels and contour lines are drawn by joining points of equal elevation 

            This method  is employed for small scale survey work of large areas.