For Profile levelling:
1) Let PQR be the given centre line.
2) Mark point at 10 m intervals on this line.
3) Level is set up on a firm ground at a suitable point I1.
4) Temporary adjustment of level is done and B.S. is taken on B.M.
5) The RL of collimation (HI) is worked out by adding B.S. to the R.L. of B.M.
The chain is stretched from P toward the point Q.
6) Also, the staff readings are taken at 10 m points, and entered in the I.S column against the respective changes.
7) Beside these points, the staff readings are taken at the representative points. for example slope of ground surface changes appreciably.
8) When it is found necessary to shift the instruments on account of the length of sight exceeding about 100 m or the further points not being possible to be observed owing to the irregularities of the ground, CP1 is taken at suitable position, and F.S is taken on it and entered in F.S column.
9) The instrument is then shifted and set up on firm ground at I2 as before.
10) B.S is taken on CP1 and new HI is calculated.
For cross Sectioning: While profile leveling is in progress, cross-sectional leveling should also be done. The cross-sections are taken perpendicular to the Centre line of the alignment at some regular intervals (say 20m, 40m etc). The purpose of cross-sectional leveling is to know the undulation of the ground surface transverse to the centre of the road.
The length depends upon the nature of the work. In case of ordinary work, the length may be 20 or 40 m on each side of the center line. The levels are taken at an interval of 5 m on each side. Additional readings may be taken if the nature of the ground surfaces suddenly changes.