Topcon OS-103 - Correction for Refraction and Earth Curvature

27. EXPLANATIONS
152
The instrument measures distance, taking into account correction for refraction and earth curvature.
Distance Calculation Formula
Distance Calculation Formula; with correction for refraction and earth curvature taken into account.
Follow the Formula below for converting horizontal and vertical distances.
Horizontal distance D = AC(α)
Vertical distance Z = BC(α)
D = L{cosα - (2θ - γ) sinα}
Z = L{sinα + (θ - γ) cosα}
θ = L
• cosα/2R : Earth curvature correcting item
g = K
• Lcosα/2R : Atmospheric refraction correcting item
K = 0.142 or 0.2 : Coefficient of refraction
R = 6371km : Radius of earth
a : Altitude angle
L : Slope distance
Changing "K (Coefficient of refraction)" value : "20.1 Observation Conditions"
27.2 Correction for Refraction and Earth Curvature
Radius of earth
R=6371km