To locate a rising gradient of 1 in 100 from the station P, a level is set up at a commanding position and back sight is taken at P. Let the back sight reading be 1.255 m. The staff reading at any point X on the contour gradient can be calculated from its distance from P (Figure 18.2). For the distance XP of 20 m, the required staff reading would be
To locate the point X on the ground, the staff man holds the 20 m-mark of the tape, keeping the zero-mark at P, and moves till the staff reading of 1.055 m is obtained. Likewise, the staff readings for other points at known distance from P, are calculated, and the points are located. If the point Q is on the contour of 105 m, its distance from P would be 500 m in this case. The instruments such as Indian clinometer, theodolite and Ghat tracer may also be used for tracing the contour gradient on the ground.