Understanding the subtle bending of light and Earth in precise surveying.
A level surface follows the Earth's shape. A surveyor's horizontal line of sight departs from this level surface as distance increases.
Light bends downwards through the atmosphere, partially offsetting the effect of Earth's curvature. It's roughly 14% of the curvature correction.
The net difference between curvature and refraction that must be applied to precise leveling.
K = Distance (km) | h = Correction (m)