Topcon GPT-7500 Series, Instruction Manual

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9 CORRECTION FOR REFRACTION AND EARTH CURVATURE
9 CORRECTION FOR REFRACTION AND EARTH
CURVATURE
The instrument measures distance, taking into account correction for refraction and earth curvature.
9.1 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
) or BE(
β
)
Vertical distance Z =BC(
α
) or EA(
β
)
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
γ
=K
•
Lcos
α
/2R....... Atmospheric
refraction
correcting item
K =0.14 or 0.2.......... Coefficient of
refraction
R =6372km.............. Radius of earth
α
( or
β
)................... Altitude angle
L .............................. Slope distance
•
The conversion formula for horizontal and vertical distances is as follows when correction for
refraction and earth curvature is not applied.
D=L
•
cos
α
Z=L
•
sin
α
The coefficient of the instrument has been set at 0.14 before shipment (K=0.14).
if the "K" value is to be changed, refer to 5 “PARAMETERS SETTING MODE”.