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2. Slope Reduction

A surveyor measures the distance between a section and quarter section corners and records a slope distance of 2677.36 ft with a zenith angle of 81°10'25" corrected for atmospheric conditions.

What error is introduced in the horizontal distance if refraction and curvature are not taken into account?

To solve this, compute the difference using Equations A-2 and B-5

From Equation A-2

c ex 2a

From Equation B-5

c ex 2b

The difference is 0.096 ft for a relative accuracy of 1/27,600.

While this is a pretty good relative accuracy, remember that this is just for an error introduced by ignoring refraction and curvature. It doesn't take into account other errors which can affect the measurement.