Correction For Refraction And Earth Curvature - Sokkia X-1000 series Operator's Manual

27.3 Correction for Refraction and Earth Curvature

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 (Ref.index)
R = 6371km : Radius of earth
a : Altitude angle
L : Slope distance

Changing Coefficient of refraction value K (Ref.index): "19.1 Observation Conditions - Angle/Tilt"
Radius of earth
R=6371km
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27. EXPLANATIONS