The formula for computing the combined effect of curvature and refraction is:
C + R = 0.021K2
Where C = correction for curvature
R = correction for refraction
K = sighting distance in thousands of feet
How to eliminate error due to Curvature and Refraction
Proper field procedures (taking shorter shots and balancing shots) can practically reduce errors
Wherever possible, staff readings should be kept at least 0.5 m above the ground,
Using short observation distances (25 m) equalized for backsight and foresight
Air below is denser than air above Air below is denser than air above, Line of sight is bent downward which Negates earth curvature error by 14%.
Simultaneous Reciprocal Trigonometrical Heighting
Observations made at each station at exactly the same time, cancels the effects of curvature and refraction
17yrs in the field of civil engineering as a land surveyor completing projects requiring dead nuts accuracy spanning tens of miles horizontally as well as hundreds of feet vertically using astonishingly precise instrumentation to calculate each known empirically definable variable including adjustments for thermal atmospheric refraction and optical refractory parallax , while maintaining tolerances as little as one one/hundredth of a foot.
Never have i visually observed, nor do my instruments indicate evidence of, and NEVER have i “adjusted” my collected observational field data or implemented any equation variable to account for a spherical geography.
The phenomenon asserting spherical global geography is not included as applied to engineering and construction in the physical world.