Lehmann's rules

1. If the position of plane table station is inside the great triangle, its plotted position should be chosen inside the triangle of error (Figure 35.3).
2. If the position of plane table station is outside the great triangle, its plotted position should be chosen outside the triangle of error (Figure 35.4).
3. The plotted position of the plane table should be so chosen that its distance from the the resectors is proportional to the distance of plane table station from the field positions of the considered objects Figure 35.4.
4. The plotted position of the plane table should be so chosen that it is to the same side of all the three rays. For example, in (Figure 35.4), as p is chosen to the right of the ray Xx, it is chosen in such a way that it is also to the right of the rays Yy and Zz.

   (4a) If the position of plane table station is outside the great circle, its plotted position should be so chosen that

   • It lies on the same side of ray to the most distant point as the intersection k of the other two rays (Figure 35.4).
   • The intersection of two rays to the nearer points, is midway between the plotted position of the station and the ray to the most distant point (Figure 35.4)..

   (4b) If the position of plane table station is outside the great triangle but inside the great circle, the plotted position of the station is so chosen that the ray to the middle point lies between plotted station position and the intersection of the rays to the two extreme points (Figure 35.5).

<< Back | Next >>