During measurement of distance, various obstacles may be encountered in the field. Depending upon the type of obstacle, a suitable geometrical figure has to be framed and an equivalent distance has to be measured or computed. Obstacles encountered in the field can be divided into three broad categories.

Type I : Ranging along obstacle is possible but not measurement such as pond, river etc.

To carry measurement along the type of obstacles where measurement round the obstacle is possible, perpendicular offsets are drawn from the line one at each side of the obstacle, as shown in Figure 8.4(a). Then, a parallel distance equivalent to distance along the obstacle is measured. In some cases, the distance is being calculated either adopting basic principle of geometry and/or trigonometric relations Figure 8.4(b).

When measurement round an obstacle is not possible, similar triangles are established as shown in Figure 8.5(a), Figure 8.5(b). The unknown distance is calculated by solving similar triangles.

<< Back | Next >>