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5. Comparing Different Measurement Sets
Two survey crews measure different horizontal angles multiple times; their results are shown in the table.
Crew A | Crew B | |
2 D/R | 4 D/R | |
Average Angle | 128°18'15" | 196°02'40" |
Std Dev | ±00°00'12" | ±00°00'14" |
D/R means to measure an angle direct and reverse; each D/R set is 2 measurements
Which crew has better precision?
Crew A because their standard deviation is smaller.
Which crew has better accuracy?
We need to determine the expected error in each crew’s average angle. Use Equation D-4.
Crew A: | |
Crew B: |
Crew B has better accuracy since the expected error in their average angle is less.