Which azimuth closure formula corresponds to a first-order network?

• A. 1.7√N
• B. 3.0√N
• C. 4.5√N
• D. 10.0√N

Answer: (A)

The key idea is that azimuth closure error grows with the square root of the number of observations, and the coefficient you use reflects how precise the network must be. A first‑order network is the most precise, so it uses the smallest coefficient.

Among common practice constants, 1.7 is the smallest, so the azimuth closure formula for a first‑order network is 1.7√N. The larger coefficients (3.0√N, 4.5√N, 10.0√N) correspond to lower‑order networks with looser tolerances, not the highest precision.

Here, N represents the number of azimuth observations in the network, so the smaller coefficient yields the smallest predicted closure error, matching the strength of a first‑order network.