Carry out contouring in the field.
Introduction
Contouring in surveying is the determination of elevation of various points on the ground and fixing these points of same horizontal positions in the contour map.
This experiment is useful to carry out contouring in the field.
Principle
- Spot elevation of various points are measured on the ground and points of equal elevation are joined by smoot line known as contour.
- In general, principle of linear interpolation is used to find out the elevation of other ground.
Equipments Used
- Level or Theodolite.
- Staff.
- Clinometer and Clinopole.
Dos and Don'ts
Dos
- Always assess the maximum and minimum elevation values in the area to be surveyed.
- Always take large number of leveling observations wherever there is a sharp change in profile and plan curvature.
- Take sufficient number of spot levels so as to cover the entire area.
- Always draw the contours in the field (when there are sufficient numbers of spot levels) as it is easy to bring out the correct shape of the contours in front of the terrain.
- Use interpolation method to draw all the contours as per desired contour interval.
Don'ts
- Do not take either very large number or very small number of spot levels, as contouring is always done by interpolation.
- Do not draw the contours with sharp spikes and turnings; instead draw them by smooth curve.
- Do not select two different contour intervals for one single area to be surveyed.