Topcon GPT-7500 Series - Correction for Refraction and Earth Curvature; Distance Calculation Formula

112
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{cosα–(2θ – γ ) sinα}
Z = L{sinα+(θ – γ ) cosα}
θ = L.cosα/2R........... Earth curvature
correcting item
γ =K
•Lcosα/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
•cosα
Z=L
•sinα
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”.