Section 4: Soil and Water Conservation Engineering
Surveying and Levelling
Subtopic: Plane table surveying
Question Statement:
In solving the three-point problem in plane table surveying by Lehmann's method of trial and error, the point sought $P$ lies outside the 'great triangle' $ABC$. If the surveyor is facing the stations, the triangle of error falls to the right of rays. The true station point $p$ must lie:
Options:
(A) To the right of all three rays (or left of all three rays) when facing the respective stations
(B) Inside the triangle of error
(C) On the circumference of the great circle passing through A, B, and C
(D) At station A
Answer Key:
A
Step-by-Step Solution & Explanation
Lehmann's rules: (1) If $p$ is outside the great triangle, it lies on the same side (all left or all right) of each of the three rays when facing the stations. (2) Its distance from each ray is proportional to the distance of the station.