When you look out over the ocean, the horizon looks like a sharp, flat line. But here’s a secret: that line isn’t always where you think it is. Depending on the weather, the horizon can actually appear higher or lower than its true physical location. This happens because the air near the ground or water is often a different temperature than the air higher up. This difference creates a gradient that bends your line of sight. This is the heart of Atmospheric Refractivity Gradient Mapping.
For a long time, surveyors and builders just had to deal with a bit of
