Example 28-2: Determine the azimuth of the sides of a open looped closed traverse (Figure 28.5) by deflection angle correction method. Solution : Figure 28.5 illustrates a closed loop traverse with deflection angles. This traverse originates and closes on traverse station A. Since, the initial and terminating station is the same, if there is no error of closure, the algebraic sum of the deflection angles should be equal to 360°. Column (1c) of Table 28.2 shows the algebraic sum of the observed values of the deflection angles as 360° 01' 40". Thus, there is an error of closure error of +1' 40". To adjust the observed angles, this error is distributed equally (20") among all the five deflection angles, assuming all angles are of equal weight. Since the sum of right deflection angles is more than the sum of left deflection angles and the error of closure is positive, so 20" is subtracted from each right deflection angle and 20" is added to the left deflection angle. Thus, the adjusted value of deflection angles are determined [Column (3) of Table 28.2]. To find the direction of the traverse lines, adjusted value of azimuth of lines are computed using the adjusted deflection angle starting from the previously observed value of azimuth of the line AB [Column (3) of Table 28.3]. Note that the observed azimuth of the starting side AB agrees with its computed value, since the angles had been adjusted before azimuth computation. Table 28.2 Adjustment of Deflection Angles (Figure 28.5)
Table 28.3 Computation of Azimuths Using Adjusted Deflection Angles (Figure 28.5)
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