13-1
13 CORRECTION FOR REFRACTION AND EARTH CURVATURE
13
CORRECTION FOR REFRACTION AND EARTH
CURVATURE
The instrument measures distance, taking into account correction for refraction and earth curvature.
13.1 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{cos
α
- (2
θ
-
γ
) sin
α
}
Z = L{sin
α
+ (
θ
-
γ
) cos
α
}
θ
= L
•
cos
α
/2R : Earth curvature correcting item
g = K
•
Lcos
α
/2R: Atmospheric refraction correcting item
K = 0.14 or 0.20: Coefficient of refraction
R = 6371km
: Radius of earth
a
: Altitude angle
L
: Slope distance
•
Changing "K (Coefficient of refraction)" value :
Radius of earth
R=6371km
