Which method is used for the preparation of a contour plan for a route survey?

Uses of indirect method of contouring:

Cross section method: This method is suitable for route survey, when cross sections are taken transverse to the longitudinal section.

Square or grid method: The method is used for large scale mapping and at average precision.

Cross section method Procedure:

- In these sections, a base line, centre line or profile line is considered

- Cross sections are taken perpendicular to this line at regular intervals

- A temporary bench mark is set up near the site

- Staff readings are taken along the base line and the cross sections

- The readings are entered in the level book the base line and the cross sections should also be mentioned

- The RL of each of the points calculated

- Then the base line and cross sections are plotted to a suitable scale

- Subsequently the RLs of the respective points are noted on the map, after which the required contour line is drawn by interpolation