(1) that offset by the tangent to the curve resulting from the curvature of the Earth. The offset of approx. 8 cm to 1 km away. (2) that offset which is given in tables as a correction to the curvature of the Earth. the values indicated in these tables usually combine the effects of both Earth's curvature and atmospheric refraction. Under normal conditions, the atmospheric refraction partially compensates for the curvature of the Earth, then the fix is about 6 cm to a point distant 1 km.