The effect of an error in the measurement of the angle q on the computed length D is as follows (Figure 24.5):
---------------- Equation (24.12)
where dD is the error in the distance D; dq is the error in the angle q. The angle q is in radians.
It may be noted that the nature of error in computation of distance is opposite to the nature of error in measurement of horizontal angle ie., a positive error in dq produces a negative error in D and vice versa.