Topcon GTS-823A Correction for Refraction and Earth Curvature, Distance Calculation Formula

12 CORRECTION FOR REFRACTION AND EARTH CURVATURE

12CORRECTION FOR REFRACTION AND EARTH CURVATURE

The instrument measures distance, taking into account correction for refraction and earth curvature.

Note: If the telescope is positioned within ±9° from the nadir or zenith, no measurement will result even if the correction function for refraction and earth curvature works.

The display shows “W/C OVER”.

12.1 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

lThe 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

Note: 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 8 “PARAMETERS SETTING MODE”.

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